Growth dynamics and sustainable development of aquatic products export trade of China and Vietnam

Abstract

The establishment of the China-ASEAN Free Trade Area has prompted closer cooperation in aquatic products trade between China and Vietnam. Studying the aquatic trade situation and export trade growth dynamics of China and Vietnam can help clarify the aquatic trade relationship between China and Vietnam and promote the sustainable development of bilateral aquatic trade cooperation. This paper analyzes the trade growth dynamics of aquatic products exported from China and Vietnam from 2002 to 2020 using the ternary marginal method. The trade growth pattern of aquatic products exported from China to Vietnam is “both quantity and price growth,” and the trade growth pattern of aquatic products exported from Vietnam to China is “quantity growth mainly, extensive growth supplemented.” The two countries have apparent differences in the growth dynamics of aquatic products export trade. Moreover, there is a higher complementarity when exporting Vietnam’s aquatic products to China than China’s aquatic products to Vietnam. Based on these, analyze the factors affecting the growth dynamics of Vietnam’s aquatic products export to China: Vietnam’s economic development level negatively affects the price index and quantity index of Vietnam’s aquatic products exported to China, and Vietnam’s aquatic product output affects the price index. China’s trade freedom positively affects the price index and negatively affects the quantity index. Finally, this paper put forward suggestions to promote the sustainable development of bilateral aquatic products trade between China and Vietnam to facilitate the formulation of relevant policies between the two countries.

Introduction

In October 2000, China first proposed the construction of the China-ASEAN Free Trade Area. In January 2010, China-ASEAN Free Trade Area was formally established. Moreover, in October 2013, President Xi Jinping proposed the “21st Century Maritime Silk Road” concept during his visit to ASEAN countries, hoping to connect China closely with coastal countries through maritime shipping channels and important port cities. These have allowed China to start trade with ASEAN, enabling bilateral trade between China and ASEAN to develop smoothly. ASEAN has become China’s third-largest trading partner, and China is ASEAN’s first-largest trading partner. The aquatic products industry has become one of the five critical areas of cooperation between the two sides. The trade value of aquatic products exported from China to ASEAN increased from USD 99 million in 2002 to USD 793 million in 2020, with an average annual growth rate of 12.27%. The trade value of aquatic products exported from ASEAN to China increased from USD 256 million in 2002 to USD 2.359 billion in 2020, with an average annual growth rate of 13.13% (Figs. 1 and 2).

Fig. 1.

Proportion of aquatic products exported by China to ASEAN countries (%)

Fig. 2.

Proportion of aquatic products exported by ASEAN countries to China (%)

As the only ASEAN country bordering China by land and sea, Vietnam’s trade cooperation with China has become increasingly close in recent years. Vietnam has become the largest trading partner of China in ASEAN countries and countries along the “Belt and Road” and the sixth largest single trading partner of China, especially in the field of aquatic products trade, which both countries have highly valued. The trade value of aquatic products exported by China to Vietnam increased from USD 119 million in 2002 to USD 134 million in 2020 (Fig. 1). The trade value of aquatic products exported by Vietnam to China increased from USD 256 million in 2002 to USD 1.087 million in 2020, with an average annual growth rate of more than 50%. Vietnam’s trade value of aquatic products exported to China accounts for 42.41% of ASEAN’s trade value of aquatic products exported to China, surpassing Indonesia and becoming the largest country in bilateral aquatic products trade between China and ASEAN (Fig. 2). Moreover, China has become the largest exporter of Vietnam’s aquatic products with a proportion of 32.59% in 2020, higher than Japan and the USA, the two traditional exporters of Vietnam’s aquatic products. Although affected by COVID-19 in 2020, Vietnam’s trade value of aquatic products exported to China only decreased by 1%. Vietnam has undoubtedly become one of the essential sources of aquatic products for China. Therefore, this paper studies the aquatic products trade situation and export trade growth dynamics of China and Vietnam, which clarifies the aquatic products trade relations between China and Vietnam and the demand and consumption direction of the aquatic products market. This conclusion will be conducive to adjusting the aquatic products trade structure and stabilizing and optimizing the industrial chain so that the aquatic products trade cooperation between the two countries can be sustainable.

Literature review

The existing literature mainly uses the constant market share (CMS) model and the trade gravity model to study the driving mechanism of export growth. Among these, the CMS focuses on the factors influencing product export growth from a macro level, so there needs to be more clarity at the micro level. This paper will use the ternary marginal method to analyze export trade growth patterns at the micro level, measuring the impact of product quality improvement or product price increase on export value or market share (Li and Dong 2019). Many scholars have used this approach to study China’s trade. Their findings show that China’s export trade growth mainly stems from the increase in export quantity and the extension of export product variety (Shi 2010; Gao et al. 2013; Lu et al. 2020). In studying agricultural trade between China and the USA, Liu and Dong (2019) find that the primary growth dynamics of China’s agricultural products export to the USA is marginal growth in quantity. However, Ding and Xiao (2019) argue that the trade growth of China’s agricultural products exported to the USA relies mainly on marginal growth in extension. In studying agricultural trade between China and Russia, the extensive margin and the quantity margin are the primary sources of growth in China’s agricultural products export trade to Russia (Zheng and Ding 2018). Studies conducted from the perspective of agricultural import trade concluded that from 1995 to 2018, the quantity margin is the main dynamic of China’s import of bulk agricultural products, so there is a need to address the structural imbalance caused by quantity deficit in bulk agricultural products (Dong and Yu 2020). In addition to analyzing national trade growth patterns, some scholars have studied the agricultural products trade carried out between China and a region. The primary dynamic of China’s agricultural products export to Southeast Asian countries is the quantity margin (Ding and Xiao 2021). The extensive margin plays a significant role in the growth of China’s agricultural products export to countries along the “Belt and Road” (Huang et al. 2018). The price margin is the main dynamic of China’s agricultural products export to Central Asia (Yang and Ding 2016). The growth pattern of China’s agricultural products exported to RCEP members is “quantity growth mainly, price growth supplemented” (Wang and Wang 2022). In addition, some scholars have used the ternary marginal method to analyze the dynamics of China’s exports of different agricultural products. In terms of aquatic products trade, from 1995 to 2015, the dynamics of China’s aquatic products export to the world and its major trading partners are mainly quantity margin (Liu et al. 2017). From 2000 to 2016, the primary dynamics of China’s aquatic products export to the USA are the intensive margin, in which the quantity margin plays a dominant role, while the influence of the price margin is also rising (Zhang and Zhao 2018). There are three stages in the growth dynamics of China’s aquatic products export according to time. The first stage is from 2000 to 2007, when China’s aquatic products export growth is the increase in export quantity. The second stage is from 2008 to 2015, when China’s aquatic products export growth dynamics change from an increase in export quantity to an increase in export price. The third stage is from 2016 to 2020 when China’s aquatic products export bottleneck and growth weakens (Mi et al. 2022). All in all, the existing literature is mainly based on regional or overall research perspective, using the ternary marginal method to analyze China’s aquatic products export growth dynamics. However, the conclusions obtained do not reflect the situation of aquatic products trade between specific countries, and most of them are from one country’s perspective, which is not in line with the reality of bilateral trade development.

The existing literature on Vietnam’s aquatic products export trade mostly studies the value added and competitiveness of exported aquatic products from the perspective of enterprises (Tuyet 2017; Ai 2018). Other literature analyzes the factors affecting Vietnam’s aquatic products export trade, including the economic size and income level of importing countries, the establishment of CPTPP agreements and preferential trade agreements, and the implementation of trade barriers such as food safety standards (Thanh and Chuong 2010; Dao and Vu 2017; Nguyen et al. 2020; Vu et al. 2020). At the same time, Vietnam’s aquatic products export trade will also have a reverse effect on domestic aquatic product output and aquatic product safety (Tung et al. 2004; Hien et al. 2008). Accordingly, there is a lack of research on Vietnam’s aquatic products export trade, and the perspective of the research is relatively single. Although some research on the factors affecting export trade, there is no decomposition of aquatic products export trade growth based on trade growth theory from the perspective of dynamic trade theory and a lack of attention to the sustainability of Vietnam’s aquatic products export (Khanh Nguyen et al. 2019). Therefore, this paper will have the following contributions: Firstly, the study of the growth pattern and dynamics of aquatic products export trade of the two countries from the perspective of export trade dynamics can provide a research paradigm for subsequent analysis of inter-country trade growth dynamics, especially for developing countries; secondly, the study of growth dynamics of Vietnam’s aquatic products export trade can complement the existing literature on Vietnam’s aquatic products export trade and enrich the existing research base on Vietnam’s aquatic products trade; thirdly, this paper focuses on the bilateral aquatic products trade of China and Vietnam. From the perspective of both countries, based on the advantages of the growth dynamics of the export trade of China and Vietnam to consider fully the differences and linkages between the growth dynamics of trade between the two countries which is more conducive to the formulation of policy consistent with the sustainable development of bilateral aquatic products trade between China and Vietnam.

The structure of this paper is arranged as follows: “Research methods and data sources” chapter will explain the research methodology and data sources and analyze the growth dynamics of aquatic products export trade of China and Vietnam in the “Analysis of the growth dynamics of aquatic products export trade of China and Vietnam” chapter. Through dynamics comparison and complementary analysis of the growth dynamics of aquatic products export trade of China and Vietnam in the “Analysis of factors influencing the growth dynamics of Vietnam’s aquatic products export trade to China” chapter, “Discussion” chapter of this paper will further explore the factors affecting the growth of aquatic products export trade. Finally, the findings are discussed and analyzed in the “Conclusion” chapter, based on which to propose countermeasures and suggestions for promoting the sustainable development of aquatic products trade between China and Vietnam.

Research methods and data sources

Ternary marginal decomposition method for export growth

Melitz (2003) pioneers a new-new trade theory that mentions the binary decomposition of trade growth: extensive growth and intensive growth (extensive margin and intensive margin). Hummels and Klenow (2005) decompose depth growth into quantity growth and price growth (quantity margin and price margin) while maintaining extensive growth, developing the binary decomposition into a ternary decomposition. Shi (2010) builds on it by further deriving the growth rates of extension, price, and quantity to study a country’s trade growth relative to the world average. In this paper, we will apply the ternary marginal model of Shi to decompose the growth of aquatic products exported from China to Vietnam and Vietnam to China to analyze their export growth pattern.

The specific formula for the extensive index is as follows:

$$EMjm=\frac{{\sum }_{i\in Ijm}prmixrmi}{{\sum }_{i\in Irm}prmixrmi}$$ 1

In formula (1), j and r denote the target and reference countries, respectively. m denotes the importing country, and I_jm and I_rm denote the set of goods exported from the target country and the reference country to country m, respectively. The economic meaning of the extensive index is the richness of the variety of commodities exported from country j to country m relative to the variety of commodities exported from country r to country m. That is, the more the variety of products exported from country j, the greater the extensive index. In studying the trade dynamics of China’s aquatic products export, I_jm denotes the set of aquatic product species exported from China to Vietnam, and I_rm denotes the set of aquatic product species exported from the world to Vietnam. In studying the trade dynamics of Vietnam’s aquatic products export, I_jm denotes the set of aquatic product species exported from Vietnam to China, and I_rm denotes the set of aquatic product species exported from the world to China. i denotes the exported aquatic product species, and p and q represent the export price and quantity of these products, respectively.

The specific formula for the intensive index is as follows:

$$IMjm=\frac{{\sum }_{i\in Ijm}pjmixjmi}{{\sum }_{i\in Ijm}prmixrmi}$$ 2

In formula (2), the economic meaning of the intensive index is the proportion of exports from country j to exports from country r among the overlapping commodity varieties exported from country j and country r to country m. That is, the greater the proportion, the greater the intensive index. In the study of the trade dynamics of aquatic products exports of China and Vietnam, IM denotes the proportion of the value of aquatic product species exported from China to Vietnam and from Vietnam to China in the value of the overlapping aquatic product species exported from the world to Vietnam and China, respectively.

The intensive index can be further decomposed into the price index and quantity index:

$$I{M}_{\mathit{jm}}=P_{\mathit{jm}}\times Q_{\mathit{jm}}$$ 3

In formula (3), $P_{\mathit{jm}}={\prod }_{i\in I_{\mathit{jm}}}{\left(\frac{p_{\mathit{jmi}}}{p_{\mathit{rmi}}}\right)}^{w_{\mathit{jmi}}},Qjm={\prod }_{i\in I_{\mathit{jm}}}{\left(\frac{q_{\mathit{jmi}}}{q_{\mathit{rmi}}}\right)}^{w_{\mathit{jmi}}}$ denote the price index and quantity index, respectively. In studying the trade dynamics of aquatic products exported from China and Vietnam, P and Q denote the price and quantity proportion of aquatic products exported from China to Vietnam and from Vietnam to China to the world export to Vietnam and China, respectively, where w_jm is the weight. The calculation formula is as follows:

$$w_{\mathit{jm}}=\frac{\frac{s_{\mathit{jm}}-s_{\mathit{rm}}}{ln{s}_{\mathit{jm}}-ln{s}_{\mathit{rm}}}}{{\sum }_{i\in I_{\mathit{jm}}}\frac{s_{\mathit{jm}}-s_{\mathit{rm}}}{ln{s}_{\mathit{jm}}-ln{s}_{\mathit{rm}}}}$$ 4

In formula (4), s_jm denotes the proportion of the export value of commodity i of country j in its total export value. s_rm denotes the proportion of the export value of commodity i exported by country r in its total export value among the commodity categories that overlap country j and country r, calculated as follows:

$$s_{\mathit{jm}}=\frac{p_{\mathit{jm}}{q}_{\mathit{jm}}}{{\sum }_{i\in I_{\mathit{jm}}}{p}_{\mathit{jm}}{q}_{\mathit{jm}}},s_{\mathit{rm}}=\frac{p_{\mathit{rm}}{q}_{\mathit{rm}}}{{\sum }_{i\in I_{\mathit{jm}}}{p}_{\mathit{rm}}{q}_{\mathit{rm}}}$$ 5

The above formula is a decomposition framework that decomposes the market share of a country’s export to a particular country into ternary margins, including the extensive index, price index, and quantity index. The formula for calculating market share R is as follows:

$$Rjm=\frac{{\sum }_{i\in I_{\mathit{jm}}}{p}_{\mathit{jmi}}{q}_{\mathit{jmi}}}{{\sum }_{i\in I_{\mathit{rm}}}{p}_{\mathit{rmi}}{q}_{\mathit{rmi}}}$$ 6

$$R_{\mathit{jm}}=E{M}_{\mathit{jm}}I{M}_{\mathit{jm}}=E{M}_{\mathit{jm}}{P}_{\mathit{jm}}{Q}_{\mathit{jm}}$$ 7

Since this paper will study the growth of China’s aquatic products export to Vietnam and Vietnam’s export to China, the market shares of the 2 years should be compared whose specific expressions are as follows:

$$\frac{W^{t+1}}{W^t}=\frac{E{X}^{t+1}}{E{X}^t}+\frac{Q^{t+1}}{Q^t}+\frac{P^{t+1}}{P^t}$$ 8

Taking the natural logarithm and dividing it by the interval years will get the decomposition of export growth dynamics. The expression is as follows:

$$G_W=G_{\mathit{EX}}+G_Q+G_P$$ 9

In formula (9), G_W denotes the average annual growth rate of the proportion of aquatic product exports from China to Vietnam and from Vietnam to China. G_EX, G_Q, and G_P denote the average annual growth rate of the extension, quantity, and price of aquatic product exports.

Scope identification of the aquatic product

The scope of aquatic products includes two major categories: primary and manufactured products. According to the HS classification method in the United Nations trade database, the primary products of aquatic products are from 0301 to 0307. The aquatic manufactured products are impossible to determine, so the products studied in this paper refer to primary products. In order to better study the extensive margin, this paper will follow the HS six-digit code for the classification of aquatic product species, including a total of 282 aquatic products (Wang 2020).

Data sources

The aquatic products trade data used in this paper are from the United Nations trade database, including all HS92 six-digit code trade value and trade net weight data of aquatic products exports from China and Vietnam from 2002 to 2020, as well as the trade value and trade net weight data of aquatic products exports from many countries in the world to China and Vietnam. The export prices are calculated based on the trade value and net weight, where the trade value is in USD, and the trade net weight is in kilograms.

Analysis of the growth dynamics of aquatic products export trade of China and Vietnam

Analysis of trade growth dynamics of China’s aquatic products export to Vietnam

Overall ternary marginal characteristics of China’s aquatic products export to Vietnam

The extensive index of China’s aquatic products exported to Vietnam has apparent fluctuations but is in an upward trend overall, among which the extensive index decreased significantly in 2008 and 2016. This phenomenon may be related to the overall world environment, such as the economic crisis. Based on the abnormal situation in 2016, the year with the most significant increase in the extensive index in 2017, with an increase of 74.79%. After that, the richness of China’s aquatic products in Vietnam’s market shows a clear trend. Vietnam’s GDP rises from 281.4 billion USD in 2017 to 343.2 billion USD in 2020, so economic development prompts Vietnam’s consumers to demand aquatic products that cannot be produced in their own country. The average annual growth rate of the extensive index from 2002 to 2020 is 0.32%, and China’s diversified aquatic products export contribution to Vietnam’s market share is low. Aquatic product diversification is not an essential dynamic of the increase in aquatic products export trade. However, the increase in the variety of aquatic products will boost China’s aquatic products export to Vietnam.

The quantity index of China’s aquatic products exported to Vietnam has an average annual growth rate of 3.40%, and its contribution rate is 49.14%. It is one of the primary growth dynamics in China’s aquatic products export trade to Vietnam and has remained between 0.01 and 0.06 for a long time. There are fluctuating changes from 2003 to 2005 and 2020 due to the impact of global health disease events, but it has less impact on China than other countries in the world.

The price index fluctuates significantly from 2002 to 2020, with an inverted “V” shape. Vietnam’s economic deterioration leads to the emergence of inflation in 2007 and the financial crisis in 2008, so China’s aquatic products export to Vietnam prices increased by 240.26%. Moreover, as a new member joining the China-ASEAN Free Trade Area in 2015, Vietnam reduced tariffs and other aspects to lower aquatic products’ export prices, so the price drops to 1.0408.

From Fig. 3, the market share of China’s aquatic products exported to Vietnam remains stable. The average annual growth rate of China’s aquatic products market share from 2002 to 2020 is 7.04%, and the overall trend is more consistent with the quantity index. It can reflect that the increase in the quantity of China’s aquatic products exports has the most significant impact on Vietnam’s market share. In Table 1, the contribution of the extensive index, quantity index, and price index to the growth of market share from 2002 to 2020 is 4.63%, 49.14%, and 46.23%, respectively, indicating that the growth pattern of China’s aquatic products export to Vietnam is “both quantity and price growth.” It is a good export trend that China’s aquatic products export trade is gradually changing from relying on quantity growth to price growth by improving product quality.

Fig. 3.

The changing trend in the growth dynamics of China’s aquatic products export to Vietnam from 2002 to 2020

Table 1.

Decomposition of the growth dynamics of China’s aquatic products export to Vietnam from 2002 to 2020

Year	Market share	Extensive index	Quantity index	Price index
2002	0.0467	0.8332	0.0705	0.7958
2003	0.2233	0.8609	0.3490	0.7432
2004	0.1061	0.5940	0.2465	0.7243
2005	0.0641	0.5399	0.1403	0.8463
2006	0.0242	0.6157	0.0469	0.8392
2007	0.0100	0.5531	0.0594	0.3034
2008	0.0136	0.4411	0.0298	1.0308
2009	0.0433	0.6740	0.0509	1.2619
2010	0.0545	0.6458	0.0356	2.3726
2011	0.0610	0.6388	0.0449	2.1267
2012	0.0441	0.6673	0.0295	2.2425
2013	0.0270	0.6285	0.0267	1.6129
2014	0.0155	0.6293	0.0163	1.5107
2015	0.0134	0.7897	0.0162	1.0408
2016	0.0146	0.4142	0.0311	1.1348
2017	0.0169	0.7240	0.0201	1.1620
2018	0.0396	0.8927	0.0348	1.2733
2019	0.0461	0.9430	0.0313	1.5612
2020	0.1702	0.8853	0.1329	1.4462
2002–2020 growth rate (%)	7.04%	0.32%	3.40%	3.19%
2002–2020 contribution rate (%)	100.00%	4.63%	49.14%	46.23%

Ternary marginal characteristics of China’s different types of aquatic products export to Vietnam

According to the overall situation of the aquatic products market, aquatic products have three major categories: The first category is fish and fish products (0301–0305); the second category is crustaceans and products (0306); the third category is mollusks and products (0307). As seen from Table 2, China’s first and third categories of aquatic products exported to Vietnam show an overall growth rate of 9.89% and 3.69%, respectively. China’s second category of aquatic products exported to Vietnam is less in the rest of the years except for a significant increase in 2003. The considerable increase in the market share of the second category of aquatic products in 2003 is the main reason for the increase in the market share of China’s aquatic products in Vietnam in that year.

Table 2.

Decomposition of export growth of different types of aquatic products from 2002 to 2020

Year	Market share			Extensive index			Quantity index			Price index
	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)
2002	0.04	0.05	0.09	0.28	0.94	0.85	0.13	0.06	0.08	1.09	0.75	1.31
2003	0.15	0.25	0.05	0.42	0.99	0.29	0.41	0.34	0.18	0.84	0.73	1.04
2004	0.04	0.17	0.04	0.35	0.85	0.15	0.12	N/A	0.16	0.81	0.19	1.50
2005	0.04	0.08	0.10	0.39	0.88	0.26	0.14	0.11	0.34	0.74	0.83	1.16
2006	0.02	0.03	0.03	0.41	0.83	0.88	0.07	0.05	0.03	0.63	0.78	1.32
2007	0.01	0.01	0.02	0.37	0.84	0.86	0.04	0.01	0.27	0.73	0.35	0.08
2008	0.02	0.01	0.01	0.37	0.83	0.35	0.05	0.01	0.03	0.95	1.26	1.23
2009	0.04	0.06	0.04	0.72	0.90	0.35	0.05	0.06	0.06	1.15	1.18	2.10
2010	0.05	0.04	0.07	0.54	0.92	0.82	0.04	0.03	0.03	2.58	1.33	2.68
2011	0.04	0.05	0.13	0.52	0.88	0.83	0.03	0.05	0.06	2.34	1.09	2.50
2012	0.04	0.02	0.09	0.55	0.83	0.80	0.03	0.02	0.05	2.78	1.33	2.14
2013	0.03	0.02	0.05	0.48	0.72	0.83	0.04	0.02	0.03	1.39	1.45	2.19
2014	0.02	0.01	0.03	0.47	0.72	0.80	0.03	0.01	0.03	1.86	0.94	1.39
2015	0.03	0.01	0.01	0.60	0.96	0.78	0.04	0.01	0.02	1.07	1.09	0.78
2016	0.03	0.01	0.02	0.55	0.20	0.82	0.05	0.01	0.01	1.12	0.96	1.40
2017	0.04	0.01	0.02	0.56	0.85	0.67	0.06	0.01	0.02	1.12	1.25	1.17
2018	0.10	0.01	0.09	0.78	0.95	0.91	0.10	0.01	0.06	1.31	0.84	1.61
2019	0.07	0.01	0.11	0.94	0.99	0.63	0.05	0.01	0.15	1.63	1.90	1.15
2020	0.23	0.01	0.17	0.88	0.86	0.96	0.21	0.01	0.09	1.29	1.49	1.97
2002–2020 growth rate (%)	9.89	−20.91	3.69	6.14	−0.42	0.60	2.63	−23.38	0.88	0.89	3.66	2.16
2002–2020 contribution rate (%)	100.00	100.00	100.00	63.55	2.07	16.73	27.25	116.10	24.22	9.20	−18.17	59.25

Note: (Abrams, 1980), (Ai, 2018), and (Dao & Vu, 2017) represent the first category, second category, and third category, respectively

From the extensive index, except for the first category of aquatic products, which has an evident growth trend, the other two categories of aquatic product export varieties keep changing. On the one hand, because the second and third categories of aquatic products cover a relatively small range of products, the diversity change significantly impacts the export of this type of aquatic products. On the other hand, these two categories of aquatic products are more obviously affected by changes in demand. The extensive index of the first category of aquatic products has increased, and the highest growth rate of the first is 6.14%. It indicates that the main reason for the growth of China’s first category of aquatic products in Vietnam’s export trade is the richness of products.

From the quantity index, the contribution of these three categories of aquatic products from 2002 to 2020 is 27.25%, 116.10%, and 24.22%, respectively. That is, no matter what type of aquatic products, quantity growth is an essential dynamic of its export growth. The quantity margin of the previous period fluctuates sharply and becomes relatively stable after 2008. However, due to the limitation of the scallop farming area and the increasing domestic demand for this product, the overall attitude of China’s second category of aquatic products (0306 fresh shellfish) export is more pessimistic.

From the price index, the growth rates of these three categories of aquatic products from 2002 to 2020 are 0.89%, 3.66%, and 2.16%, respectively. The trend of price margins for various aquatic products is more consistent with the overall price margins. The price margins are upward, especially after 2008, when the price index is mostly higher than 1. It shows that the prices of various types of aquatic products exported by China have been slightly higher than the world average for a long time. It indirectly shows that the quality of aquatic products exported by China has improved and gradually changed to a “winning by quality” growth pattern to enhance the competitiveness of aquatic products.

In summary, the first category of aquatic products export trade follows the growth pattern of “extensive growth mainly, quantity growth supplemented.” The second category of aquatic products export growth depends entirely on quantity growth. The third category of aquatic products export trade follows the growth pattern of “price growth mainly, quantity growth supplemented.”

Analysis of trade growth dynamics of Vietnam’s aquatic products exports to China

Overall ternary marginal characteristics of Vietnam’s aquatic products exports to China

The extensive index of Vietnam’s aquatic products export to China is in the range from 0.5 to 0.85, which fluctuates slightly. In 2004, 2013, and 2020, the extensive index shows significant decreases, that is, the reduction in the variety of aquatic products exported, which is caused by major public emergencies such as SARS and product price competition, according to a report by the Vietnam Department of Fisheries. The year with the most significant increase in the extensive index is 2010, with an increase of 16.80%, and the average annual growth rate of the extensive index from 2002 to 2020 is −1.08%, which has a hindering effect on the export of Vietnam’s aquatic products to China’s market.

The overall quantity index of Vietnam’s aquatic products exports to China is relatively stable and roughly the same as the market share trend, with the most significant growth rate in 2013, which is more than twice the previous year. The average annual growth rate of the quantity index is 3.09% from 2002 to 2020, which is the most significant contribution to market share growth. The contribution rate is always the highest among the indicators. It shows that the trade growth of Vietnam’s aquatic products exports to China mainly bases on quantity growth. That is, Vietnam increases aquatic products’ export value and market share in China through increasing export quantity.

The price index of Vietnam’s aquatic products exports to China fluctuates significantly, remaining above 1 in all years except 2020. As can be seen from Fig. 4, the trends of the quantity index and the price index are generally opposite. However, the price index changes more sharply, resulting from a combination of factors such as the increase in aquatic products feed prices, changes in breeding technology, foreign exchange rates, tariffs, and non-tariff barriers. This phenomenon also indirectly confirms that the growth of Vietnam’s aquatic products trade to China is less affected by prices, which is why its export prices fluctuate frequently.

Fig. 4.

The changing trend in the growth dynamics of Vietnam’s aquatic products exports to China from 2002 to 2020

The market share of Vietnam’s aquatic products exported to China has remained stable and increased slightly, with an average annual growth rate of 0.72% from 2002 to 2020. Among them is the year with the largest market share in 2017, when the export trade value of Vietnam’s aquatic products to China accounted for a significant breakthrough in the proportion of ASEAN. Vietnam becomes the ninth largest importer of China’s aquatic products in that year when the share of Vietnam’s aquatic products in China’s market is as high as 13.23%. The most significant increase in market share is in 2020, with an increase of 68.80%. Although Vietnam’s aquatic products exports have also declined under the impact of COVID-19, compared with other countries in the world, its trade cooperation with China in aquatic products is relatively stable, so it has achieved a counter-trend increase in market share. Without considering the impact of the “black swan” incidents of COVID-19 in 2020, the contribution of the extensive index, quantity index, and price index to market share growth from 2002 to 2019 is 16.08%, 75.07%, and 9.36%, respectively. It indicates that the trade growth pattern of Vietnam’s aquatic products exports to China is “quantity growth mainly, extensive growth supplemented” (Table 3).

Table 3.

Decomposition of growth dynamics of Vietnam’s aquatic products exports to China from 2002 to 2020

Year	Market share	Extensive index	Quantity index	Price index
2002	0.1236	0.8389	0.1268	1.1627
2003	0.0483	0.8240	0.0506	1.1600
2004	0.0390	0.6377	0.0472	1.2968
2005	0.0383	0.7065	0.0462	1.1744
2006	0.0317	0.5885	0.0396	1.3591
2007	0.0298	0.5523	0.0450	1.1998
2008	0.0311	0.6021	0.0477	1.0821
2009	0.0376	0.6178	0.0389	1.5629
2010	0.0364	0.7216	0.0368	1.3724
2011	0.0415	0.6629	0.0328	1.9059
2013	0.0625	0.5271	0.1120	1.0581
2014	0.0689	0.6245	0.0997	1.1068
2015	0.0682	0.6338	0.0555	1.9387
2016	0.0958	0.7263	0.1030	1.2804
2017	0.1323	0.7118	0.1452	1.2797
2018	0.0884	0.7456	0.0848	1.3987
2019	0.0827	0.7869	0.0938	1.1201
2020	0.1396	0.6895	0.2193	0.9231
2002–2019 growth rate (%)	−2.49%	−0.40%	−1.87%	−0.23%
2002–2019 contribution rate (%)	100.00%	16.08%	75.07%	9.36%
2002–2020 growth rate (%)	0.72%	−1.08%	3.09%	−1.27%
2002–2020 contribution rate (%)	100.00%	−160.31%	457.88%	−188.38%

Note: Due to the lack of data on Vietnam’s aquatic products export trade in 2012, the decomposition of the growth dynamics of Vietnam’s export to China in 2012 is not reflected in Table 1

Ternary marginal characteristics of China’s different types of aquatic products export to Vietnam

As seen from Table 4, Vietnam’s first and second categories of aquatic products export to China show growth rates of 2.83% and 5.33%, respectively. The typical third category of aquatic products includes squid and sepia. Due to China’s increasingly strict regulation of imported food, many enterprises have stopped buying Vietnam’s dried squid. Furthermore, restricted by the supply of raw materials for domestic production and the high sea freight rate, the third category of aquatic products has a slightly lower market share in China. The proportion of Vietnam’s aquatic products in China’s market fluctuates wildly. For example, the market share of the second category of aquatic products in China is only 1% in 2011 but 23% in 2017, which indirectly indicates that Vietnam’s aquatic products exported to China are greatly influenced by market supply and demand on the one hand. On the other hand, Vietnam’s aquatic products are highly substitutable worldwide.

Table 4.

Decomposition of export growth of different types of aquatic products from 2002 to 2020

Year	Market share			Extensive index			Quantity index			Price index
	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)	(Abrams, 1980)	(Ai, 2018)	(Dao & Vu, 2017)
2002	0.12	0.07	0.32	0.84	0.99	1	0.13	0.05	0.20	0.83	1.32	1.58
2003	0.05	0.02	0.23	0.82	0.99	1	0.03	0.02	0.14	0.73	1.35	1.64
2004	0.04	0.02	0.18	0.64	0.54	1	0.02	0.02	0.11	1.03	1.74	1.73
2005	0.04	0.03	0.18	0.71	0.64	0.85	0.02	0.03	0.15	0.90	1.60	1.39
2006	0.03	0.03	0.12	0.59	1	0.88	0.04	0.02	0.07	1.05	1.61	1.88
2007	0.03	0.03	0.08	0.55	0.95	0.90	0.03	0.02	0.09	1.30	1.48	0.99
2008	0.03	0.07	0.06	0.60	0.92	0.93	0.03	0.05	0.08	1.15	1.38	0.81
2009	0.04	0.16	0.03	0.62	0.93	0.79	0.02	0.11	0.01	1.34	1.54	2.83
2010	0.04	0.16	0.03	0.72	0.99	0.93	0.02	0.11	0.01	1.20	1.40	1.89
2011	0.04	0.01	0.05	0.66	0.77	0.78	0.02	0.13	0.04	1.02	0.10	1.48
2013	0.06	0.18	0.02	0.53	0.69	0.45	0.05	0.28	0.02	0.92	0.96	2.37
2014	0.07	0.18	0.02	0.62	0.83	0.94	0.07	0.17	0.01	0.87	1.30	2.06
2015	0.07	0.13	0.02	0.63	0.78	0.85	0.02	0.16	0.01	3.93	1.06	2.56
2016	0.10	0.16	0.01	0.73	0.98	0.85	0.13	0.12	0.01	1.11	1.37	2.27
2017	0.13	0.23	0.04	0.71	0.87	0.99	0.13	0.24	0.01	1.312	1.10	2.58
2018	0.09	0.08	0.03	0.75	0.87	0.95	0.13	0.06	0.02	1.29	1.54	1.61
2019	0.08	0.07	0.01	0.79	0.98	0.95	0.22	0.05	0.01	0.93	1.26	1.69
2020	0.14	0.17	0.13	0.69	0.96	0.94	0.26	0.18	0.14	0.87	1.00	0.99
2002–2020 growth rate (%)	2.83	5.33	−5.30	−1.59	−0.18	−0.31	4.21	7.25	−2.34	0.27	−1.61	−2.70
2002–2020 contribution rate (%)	100.00	100.00	100.00	−56.04	−3.42	5.80	148.75	136.04	44.21	9.41	−30.23	50.93

Note: (Abrams, 1980), (Ai, 2018), and (Dao & Vu, 2017) represent the first category, second category, and third category, respectively

From the extensive index, the highest growth rate of the third category of aquatic products indicates that this category relies heavily on product diversification to achieve trade growth. In contrast, other aquatic products do not have obvious advantages in terms of product richness, or even product variety cannot meet the market demand for aquatic products in China. Except for 2013, the extensive index of the third category of aquatic products has maintained a high level, even reaching 1, indicating that Vietnam’s exports of the third category of aquatic products fully encompass China’s demand for the third category of aquatic products.

From the quantity index, the contribution of these three categories of aquatic products from 2002 to 2020 is 148.75%, 136.04%, and 44.21%, respectively. No matter what category of aquatic products, quantity growth is the most critical dynamic of its export growth.

From the price index, the growth rate and contribution rate of the price index of the second category of aquatic products are negative. The price decrease is the main reason for the decrease in the market share of Vietnam’s second category of aquatic products in China. The price index of the first category of aquatic products shows abnormal values in 2015. According to the data, China’s demand for live, frozen fish such as tuna and basa fish surges that year, so the price is higher than the world average. Because the economic crisis and the epidemic affect the price index around 2008 to 2020, in the rest of the year, the price index of the third category of aquatic products is more than 1, reaching a peak of 2.83. It indicates that with the continuous improvement of breeding technology, the third category of aquatic products has gradually changed from “winning by quantity” to “winning by quality.”

To sum up, the export trade of the first category of aquatic products follows the growth pattern of “quantity growth mainly, price growth supplemented.” The export growth of the second category of aquatic products depends entirely on quantity growth. The export trade of the third category of aquatic products follows the growth pattern of “quantity and price growth synergetic promotion.” Vietnam has a significant advantage in China’s market by continuously improving the quality of the third category of aquatic products, thus promoting the upgrading and transformation of Vietnam’s export trade pattern. China’s exports to Vietnam of various types of aquatic products growth dynamics pattern are slightly different from Vietnam’s exports to China, especially the first category of aquatic products. China’s exports of the first category of aquatic products are more diversified dynamics, to a certain extent to reduce the risk of external shocks.

Comparative analysis of the growth dynamics of aquatic products export trade of China and Vietnam

Dynamic distribution evolution of the growth dynamics of aquatic products export trade of China and Vietnam

The kernel density estimation method is a non-parametric estimation method, which eliminates the assumption of the overall distribution and can better reflect the data distribution and dynamic evolution. So the kernel density estimation method is used to examine the dynamic distribution evolution of bilateral aquatic products export trade of China and Vietnam more specifically (Fig. 5).

Fig. 5.

Dynamic distribution evolution of the growth dynamics of aquatic products export trade of China and Vietnam from 2002 to 2020

The increase in the market share of aquatic products exported from China to Vietnam is higher than that of aquatic products exported from Vietnam to China. However, the difference in the bilateral aquatic products export trade share is insignificant, and the difference in export market share fluctuates less each year. From the peak of the distribution curve in the kernel density diagram, the difference between the two countries’ bilateral trade in aquatic products is negligible when the peak is the largest. Moreover, the difference between the two countries’ export shares in aquatic products is gradually decreasing. The richness of aquatic product species exported from China to Vietnam is higher than the richness of aquatic product species exported from Vietnam to China. However, aquatic species exported from Vietnam each year are mostly the same. In contrast, the difference in aquatic product species in bilateral export trade between the two countries is enormous. The increment of aquatic products exported from China to Vietnam is lower than those exported from Vietnam to China. The relatively significant difference in the quantity of bilateral aquatic products exported and the curve is more volatile, which is similar to the market share curve in distribution, indicating that the quantity of aquatic products exported has a noticeable pulling effect on export growth. From the peaks of the distribution curve in the kernel density diagram, the bilateral aquatic trade between China and Vietnam varies significantly in terms of export quantity each year. However, there are multiple peaks, and the difference in aquatic products export quantity between years shows alternating changes of increase and decrease, among which the quantity of aquatic products exported from Vietnam to China changes frequently. The price increase of aquatic products exported from China to Vietnam is lower than those exported from Vietnam to China. The price difference between bilateral aquatic products exported from China and Vietnam is enormous. The peak of the price index of aquatic products exported from China to Vietnam is from 1 to 1.5, which indicates that the price difference of aquatic products exported from China to Vietnam is slightly higher than the world average in most cases. It reflects that China’s aquatic products export trade has started to move away from “winning by quantity” to “winning by quality.” The price of aquatic products exported from Vietnam to China varies significantly yearly, undeniably correlated with the supply and demand situation each year. In general, the dynamic distribution shows that the growth pattern of China’s aquatic products exports to Vietnam is different from that of Vietnam’s exports to China, especially in terms of export types and prices. Based on the apparent differences in the growth dynamics of the aquatic products export trade between China and Vietnam, an in-depth investigation is made into whether there is a complementary between the aquatic products export trade between China and Vietnam.

Complementary analysis of bilateral trade in aquatic products of China and Vietnam

The economist Drysdale and Garnaut (1982) proposes the complementary trade index trade to calculate the closeness of trade between two countries or regions, expressed by the formula: C_ijk = RCA_xik × RCA_mjk. Where RCA_xik denotes the comparative advantage of country i in product k as measured by exports, expressed by the formula: RCA_xik = (X_ik/X_i)/(W_k/W); RCA_mik denotes the comparative advantage of country j in product k as measured by imports, expressed by the formula: RCA_mjk = (M_jk/M_j)/(W_k/W). X_ik and M_ik denote the country i’s exports and imports in category k products, respectively. X_i and M_i denote the exports and imports of all products in country i. W_k denotes total world exports in category k products, and W denotes total world exports. In general, the larger the value of C_ijk, the higher the trade complementary of the two countries, and the smaller the value of C_ijk, the lower the trade complementary of the two countries.

The results in Table 5 show that China and Vietnam’s complementary aquatic products trade is very high. The average value of the complementary index of China’s aquatic products export and Vietnam’s aquatic products import is 0.8926, and the average value of the complementary index of Vietnam’s aquatic products export and China’s aquatic products import is as high as 6.8364. Although the complementary index decreases year by year, the complementary index is not less than 2.8, reflecting the strong complementary between Vietnam’s aquatic products export and China’s import. Thus, it is necessary to analyze further the factors affecting the growth dynamics of Vietnam’s export trade to China to realize better the sustainable bilateral development of aquatic products trade between China and Vietnam.

Table 5.

Complementary index of bilateral trade in aquatic products between China and Vietnam from 2002 to 2020

China’s aquatic products export — Vietnam’s aquatic products import
2002	2003	2004	2005	2006	2007	2008	2009	2010	2011
0.9471	0.8337	1.0789	0.9790	0.8369	0.6398	0.6664	0.7205	0.7564	1.0384
2012	2013	2014	2015	2016	2017	2018	2019	2020	均值
1.1602	1.0476	1.2276	1.0022	0.8929	0.8908	0.8458	0.7468	0.6485	0.8926
Vietnam’s aquatic products export — China’s aquatic products import
2002	2003	2004	2005	2006	2007	2008	2009	2010	2011
14.1939	12.0587	10.5753	10.6694	11.1107	10.5201	9.9215	7.3083	6.2198	5.8822
2012	2013	2014	2015	2016	2017	2018	2019	2020	均值
4.7675	4.0214	3.7089	3.0583	2.8111	2.7613	3.3037	4.0136	2.9866	6.8364

Analysis of factors influencing the growth dynamics of Vietnam’s aquatic products export trade to China

Based on the previous study, the trade growth dynamics of Vietnam’s exports to China are mainly quantity growth. The complementary of Vietnam’s exports of aquatic products and China’s imports of aquatic products is higher than that of China’s exports of aquatic products and Vietnam’s imports of aquatic products. Therefore, it is necessary to explore further the factors influencing the trade growth dynamics of Vietnam’s aquatic products export to China. In this paper, we mainly consider the economic factors and trade factors that affect the growth dynamics of Vietnam’s trade in exported aquatic products: In terms of economic factors, Abrams (1980) argues that the trade potential of a country can be measured by the level of economic development, the higher economic development level of the importing country, the higher the consumption level of people will be, and the greater the demand for a specific product. The higher economic level of the exporting country may have an indirect impact on the scale of trade. A potential increase in total supply will stimulate trade export potential. In the development of bilateral trade, the larger the economic scale and the stronger the economic strength of the two countries, the more conducive it is to the development of bilateral trade. Therefore, this paper takes the GDP of both countries as the influencing factor indicator, considering the exporting country’s supply, and takes the domestic aquatic product output as the influencing factor. Another critical factor affecting the growth dynamics of bilateral trade is the trade factor. This paper considers trade freedom and the level of trade facilitation. Grossman and Helpman (1995) argue that the reason for the formation of free trade depends on the domestic political environment. The government will choose the trade policy that maximizes the sum of the weighted welfare of interest groups and the population. Usually, the higher the trade freedom, the more conducive to bilateral trade. Iwanow and Kirkpatrick (2007) show that exports will increase with the level of trade facilitation. Therefore, the effect of trade facilitation on the growth dynamics of trade in Vietnam’s aquatic products exported to China is considered. The data sources for each variable are as follows: The data on the growth dynamics of Vietnam’s aquatic products export trade to China, including the extensive index (EM), price index (P), and quantity index (Q), are obtained from the previous calculations; the data on the level of economic development of Vietnam and China, that is GDP of Vietnam (GDPV) and GDP of China (GDPC), and Vietnam’s aquatic product output (PRO) are obtained from the World Bank’s WDI database; Vietnam’s trade freedom data are obtained from the annual report of The Heritage Foundation Index of Economic Freedom; China’s trade facilitation level (TFI) data are obtained from the measurement data of related research literature.

Since the data selected in this paper are time series, it is necessary to test the variables’ robustness to eliminate the “pseudo-regression” and obtain the long-term equilibrium relationship between variables. This paper adopts the ADF method in the unit root test. Trade freedom is a stationary series, the price index, quantity index, and trade facilitation have a first-order cointegration relationship, respectively, and trade facilitation is a static variable after the third-order difference. Accordingly, a general linear regression is conducted to obtain the factors affecting the growth dynamics of Vietnam’s aquatic products export trade to China. The specific regression results are shown in Table 6.

Table 6.

Results of the empirical analysis of factors influencing the growth dynamics of Vietnam’s aquatic products export trade to China

	EM	D.P	D.Q
GDPC	−0.6601 (0.9320)	3.4127 (2.3769)	0.2264 (0.1354)
GDPV	0.7796 (0.9903)	−6.7291** (2.5013)	−0.3474* (0.1551)
PRO	−0.4108 (0.7032)	4.0816** (1.6175)	0.1645 (0.1404)
FREE	0.0467 (0.070)	0.3298** (0.1187)	−0.0144* (0.0076)
TFI
D.TFI		−5.8132 (4.0086)	0.7265 (0.4417)
D3.TFI	0.0722 (0.4706)
C	3.0698 (4.6770)	−34.0752 (19.6346)	−0.5089 (1.6224)
R2	0.2302	0.7673	0.6190

Note: Robust standard deviations of the corresponding variables are in parentheses, and ***, **, and * indicate significance at 1%, 5%, and 10% significance levels, respectively. The t-value magnitude is shown in parentheses

From the regression results in Table 6, each influencing factor has a negligible effect on the extensive index in the growth dynamics of Vietnam’s aquatic products export to China, which are all insignificant. It indicates that economic and trade factors hardly influence trade growth prompted by the increase in product variety. The quantity index, as the central dynamics of trade growth, is influenced by the size of Vietnam’s economy. With the expansion of economic scale, people’s living standard increases, and the demand for aquatic products increases, which makes the domestic supply of aquatic products increases and the quantity of aquatic products exported to China decreases. Thus, the size of Vietnam’s economy negatively affects the quantity margin of aquatic product exports. Moreover, the expansion of Vietnam’s economic scale reduces the price margin. That is, the production technology and the division of labor tend to be improved, the ability to produce aquatic products is improved, and the price of exported aquatic products is reduced. China’s trade freedom also has a significant negative impact on the quantity margin of Vietnam’s aquatic products exports. Higher trade freedom means that the country’s relevant system is more sound than others. The higher the degree of openness, the lower the trading threshold for import and export, the more aquatic products can enter the country and the more intense competition. The international competitiveness of Vietnam’s aquatic products is not strong, hurting the quantity margin of exported products to some extent. It positively impacts the price margin, indicating that Vietnam is more likely to export higher quality or higher-end aquatic products to China due to the impact of world aquatic products export competition, so the price index has increased. In the long run, it is urgent to optimize the structure of Vietnam’s aquatic products export to make Vietnam’s aquatic products more competitive in the international market. The increase in Vietnam’s aquatic product output is conducive to improving the price index, and its price changes are more reflected in the costs. Due to the rising prices of aquatic product feed, the upgrading of breeding technology, and the continuous vibration of foreign exchange rates, they can raise the cost of aquaculture in Vietnam. Therefore, the increase in output driven by the increase in expenses will increase the price of Vietnam’s aquatic products exports.

Discussion and conclusion

Discussion

In terms of studying the growth dynamics of aquatic products export trade of China and Vietnam, this paper uses the ternary marginal model to conduct an empirical analysis, which expands the research field of international trade growth dynamics and provides a reference for promoting the development of bilateral aquatic products trade cooperation between China and Vietnam. Specifically, this paper enriches the existing research foundation of Vietnam’s aquatic product trade, which will be conducive to the study of the sustainable development of bilateral aquatic products trade between China and Vietnam. According to this paper, the growth pattern of China’s aquatic products export trade to Vietnam is “both quantity and price growth.” This is consistent with the research conclusions of Liu et al. (2007) that the export dynamics of China’s aquatic products to the world and its major trading partners are mainly quantitative marginal. However, this conclusion is different from the research conclusions of Wang (2020) that China’s aquatic products export to Vietnam follows the growth model of “price growth mainly, extensive growth as the supplement.” The reason for this difference is that the period of the research is different. The period of Wang’s research is from 2002 to 2018, while the research span of this paper is from 2002 to 2020. Although there is only a 2-year difference, according to the research of Mi et al.(2022), it can be seen that the growth dynamics of China’s aquatic products export has very significant phased characteristics. This is also a place for further research, that is, to analyze in detail the phased characteristics of the growth dynamics of China’s aquatic products exported to Vietnam. Moreover, this paper has another limitation. Due to the limited amount of data collected, the author can only obtain the HS six-digit code of aquatic products through the United Nations trade database, it is impossible to carry out detailed research on key aquatic product species. Based on this, the author hopes to make up for this limitation by using relatively microscopic data in the future. Besides, it has practical policy significance to analyze the dynamics of other countries’ aquatic products export to China, such as Indonesia. These will become the focus of the author’s future research. And the author will also conduct more in-depth research about aquatic products trade based on the existing research results and from the perspective of China-ASEAN.

In terms of studying the sustainable development of aquatic products export trade of China and Vietnam, in order to achieve sustainable development of China’s aquatic products exported to Vietnam, it is necessary to continue to improve the international competitiveness of aquatic products. Although China’s aquatic products export trade pattern has begun to “winning by quality” transformation, the overall global competitiveness of China’s aquatic products still lacks stability (Liu et al. 2017). Therefore, it is more critical to expand through brand marketing and targeted marketing of China’s aquatic products in Vietnam’s market share. The second category of aquatic products should accelerate the export transformation, not simply rely on quantity export to promote trade growth. In order to achieve sustainable development of Vietnam’s aquatic products exported to China, it is necessary to adjust the structure of aquatic products exported, especially the continuous improvement of the extensive index of Vietnam’s aquatic products exported to China, vigorously promote advanced breeding technology, and increase the development of new species. Besides, it is essential to improve the added value of exported aquatic products to achieve “winning by quality.” For a long time, quantity growth has dominated the growth of Vietnam’s aquatic products export trade, which will be highly substitutable. It is vital to alter the extensive growth pattern, encourage China to import Vietnam’s aquatic products due to their high quality, and convert cost advantages into product advantages to improve the value of aquatic products. Among them, the deep processing of aquatic products is the key to increasing their added value. Aquatic product enterprises can increase investment in scientific research and rely on scientific and technological progress to improve the processing technology of aquatic products. Moreover, they need to extend the deep processing industrial chain of aquatic products and gradually change from primary products to deep processing direction (Zhang and Zhao 2018).

Conclusion

The growth pattern of China’s aquatic products export trade to Vietnam is “both quantity and price growth.” Among these, the first category of aquatic products export trade follows the growth pattern of “extensive growth mainly, quantity growth supplemented.” The second category of aquatic products export growth depends entirely on quantity growth. The third category of aquatic products export trade follows the growth pattern of “price growth mainly, quantity growth supplemented.” The growth pattern of Vietnam’s aquatic products export trade to China is “quantity growth mainly, extensive growth supplemented.” Among these, the first category of aquatic products export trade follows the growth pattern of “quantity growth mainly, price growth supplemented.” The second category of aquatic products export growth depends entirely on quantity growth. The third category of aquatic products export trade follows the growth pattern of “quantity and price growth synergetic promotion.” From the dynamic distribution, there are apparent differences between the growth dynamics of China’s aquatic products export to Vietnam and Vietnam’s aquatic products export to China, especially in terms of export types and export prices. Therefore, further analysis of the complementary of China-Vietnam trade in aquatic products shows that the complementary of China-Vietnam trade in aquatic products is very high, especially the highest complementary when Vietnam exports aquatic products and China imports aquatic products. By analyzing the factors that influence the growth dynamics of Vietnam’s aquatic products export to China, this paper concludes that the level of economic development of Vietnam negatively affects the price index and quantity index of Vietnam’s aquatic products export to China. Vietnam’s aquatic product output affects the price index of Vietnam’s aquatic products exports to China, and the trade freedom in China positively affects the price and quantity index of Vietnam’s aquatic products exports to China.

Author contribution

All authors contributed to the study conception and design. XW and YX performed material preparation, data collection, and analysis. XW wrote the first draft of the manuscript, and LW commented on previous versions and gave some suggestions. All authors read and approved the final manuscript.

Declarations

Ethical approval

This article does not contain any studies with animals performed by any of the authors.

Competing interests

The authors declare no competing interests.