Table 4. Modelled (FSR_mod) and observed (FSR_obs) fertilization success for each urchin pair under acidified conditions (pH 7.6 and 7.8), and parameters from Control observations (pH 8.1) used in modelling FSR_mod at lowered pH levels.

pH	7.6		7.8		8.1
Pair/Male	FSRmod (%)	FSRobs (%)	FSRmod (%)	FSRobs (%)	FSR50 Control (%)	F 50 Control (sperm µl−1)
A	no data
B	26.46	63.92	25.33	50.38	28.95	1258.93
C	36.21	47.93	55.81	47.19	47.76	1584.89
D	23.25	10.46	24.45	12.95	24.94	4466.84
E	41.34	45.80	43.21	62.59	37.03	3162.28
F	51.59	24.21	50.45	37.27	49.74	7943.28
G	41.55	44.83	42.74	46.93	48.98	2511.89
H	38.78	61.78	39.09	51.80	47.37	22387.21
I	41.52	9.05	43.45	7.11	42.03	251.19
J	3.74	30.15	3.50	2.47	31.94	398.11
K	38.95	71.08	41.06	53.18	48.64	22387.21
L	40.78	64.17	41.26	60.09	48.06	10000.00
M	28.60	40.79	30.54	35.49	34.61	2511.89
N	52.12	47.55	53.29	53.32	48.81	3981.07
O	35.89	43.26	37.83	43.39	42.95	10000.00
P	43.72	28.96	41.66	52.20	49.88	50118.72
Q	49.49	22.29	49.71	41.97	48.26	8912.51
R	50.57	54.19	47.54	63.00	46.58	15848.93
S	54.44	76.84	53.87	49.54	50.77	2238.72
mean	38.83	43.74	40.27	42.83	43.18	9442.43
S.E.	2.93	4.68	3.02	4.24	1.91	2898.53

FSR_{50 Control} = 50% of maximum fertilization success in Controls; F _{50 Control} = sperm concentration that generates 50% of maximum fertilization success in Controls. Sperm data from each male in Table 2 were used in modelling FSR_mod. No females were spawned for male A.