Because batch fecundity is positively correlated with fish size (Lowerre-Barbieri et al., 2015), relative batch fecundity (RBF, number of eggs/g ovary-free body weight) was used in all models to remove the influence of fish size and was calculated as batch fecundity divided by ovary-free body weight.
Values ranged from 0.179 eggs/g ovary-free body weight in 1994 to 394.0 eggs/g ovary-free body weight in 2013 in the northeastern GOM and 0.048 eggs/g ovary-free body weight in 1998 to 557.39 eggs/g ovary-free body weight in 2001 in the northwestern GOM.
Estimated mean (50% confidence interval [lower-upper as 25% and 75% CI]) RBF values for regions combined were initially 58.0 (45.8-71.4) eggs/g ovary-free body weight in 1991, increased to 83.8 (74.4-93.5) eggs/g ovary-free body weight in 2001, then decreased to 35.7 (29.1-43.1) eggs/g ovary-free body weight in 2017 (Fig.
The relative number of oocytes per gram of female (RN) was calculated by dividing N by the ovary-free body weight. Unlike the equation originally developed by Kurita and Kjesbu (2009), the stage-specific oocyte packing density ([OPD.sup.i]) in this study was simplified by dividing N of stage i oocytes by the ovary weight.
N, oocytes per ovary; RN, oocytes per gram of ovary-free body weight.
Relative fecundity (RF, number of hydrated oocytes per gram of ovary-free body weight
) was estimated as the batch fecundity divided by female weight (without ovaries).
Mean relative batch fecundity was 107.8 eggs/g ovary-free body weight (standard error 17.1).
The RBF ranged from 31.1-328.3 eggs/g ovary-free body weight with an overall mean of 107.8 eggs/g ovary-free body weight (SE 17.1; median: 101.7).
Relative fecundity (RF) was defined as the number of hydrated oocytes per gram of ovary-free body weight. Fecundity values obtained for the different months within the spawning season were compared with a test of equality of means (Draper and Smith, 1981).
The relationship between batch fecundity and ovary-free body weight was linear (Fig.
Batch fecundity calculated with the NBF method showed a positive relationship with fork length (P=0.021, [r.sup.2]=0.132) and ovary-free body weight (OFBW; P=0.016, [r.sup.2]=0.143).
In all cases, fecundity was expressed as both batch fecundity (mean number of eggs/batch) and relative fecundity (number of eggs/gram of ovary-free body weight).