Table 1. Variables and model selection.
A) | ||||||||
Variables | Description | |||||||
Depth | Measured from sea surface to the ocean floor (meters) | |||||||
Sea surface salinity (SSS) | Average salinity from each station from 0–50 meters (parts "per mille"—ppt) | |||||||
Sea surface temperature (SST) | Average temperature from each station from 0–50 meters (°C) | |||||||
Zooplankton biomass | Dry weight from WP2 hauls at each station (mg/m3) | |||||||
Fulton's K | Fulton's condition factor (K = 100(W/L3) | |||||||
Latitude and longitude | Geographical marker of stations | |||||||
Total catch | Log transformed total mackerel catch (ton) per station | |||||||
Week | week number during the survey | |||||||
Time of day | Day divided into four time periods with 6 hours in each (00:00–05:00, 06:00–11:00, 12:00–17:00, 18:00–23:00) | |||||||
Year | Data collected from 2011–2014 | |||||||
Distance to shore | From isobath lines (≤100m, ≤200m, ≤500, >501m) | |||||||
B) | ||||||||
Model # | Response variable Explanatory variable | Factorial variables | AIC | ΔAIC | wi | Deviance explained | R2 adjusted | DF |
1 | log(stomach weight) zooplankton + (longitude,latitude)+ Fulton´s K+ depth + SSS + SST + log(total catch) | time period+distance to shore+week+year | -1854 | 8.92 | 0.007 | 48.50% | 0.44 | 153 |
2 | log(stomach weight) zooplankton + (longitude,latitude)+ depth + SSS + SST + log(total catch) | time period+distance to shore | -1863 | 0 | 0.58 | 48.60% | 0.44 | 150 |
3 | log(stomach weight) zooplankton + (longitude,latitude) + SSS + SST + log(total catch) | time period | -1862 | 1 | 0.35 | 48.50% | 0.44 | 148 |
4 | log(stomach weight) zooplankton + (longitude,latitude)+ depth+ SSS + SST | time period | -1860 | 4.4 | 0.06 | 48.30% | 0.42 | 147 |
A) List of explanatory variables considered in analyses of Northeast Atlantic mackerel stomach weight in Icelandic waters in 2011–2014 using generalised additive models (GAMs). B) GAMs selection table, the model marked in bold was found to be the best-fitted model based on Akaike Information Criterion (AIC) from the R package “MuMIn” (see Table 6).