Figure 1.
Map indicating locations where samples were collected from South Pacific albacore.
Localities are shown for active female (red crosses), inactive or immature female (orange squares) and male (blue circles).
Table 1.
Number of South Pacific albacore gonads sampled by region.
Figure 2.
Histological sections of ovaries showing examples of development classes, oocyte stages and postovulatory follicles (POF).
(A) unyolked oocytes in an immature ovary, (B) advanced yolked oocytes in a spawning capable ovary, (C) migratory nucleus oocyte in a spawning ovary, (D) hydrated oocytes in a spawning ovary, (E) <12 hour POF in a spawning ovary, (F) >12 hour POF in a spawning ovary. UY = unyolked, EY = early yolked, AY = advanced yolked, MN = migratory nucleus, H = hydrated. The scale bars are 200 µm (black) and 100 µm (white).
Figure 3.
Histological sections of ovaries showing examples of development classes and maturity markers.
(A) alpha and beta atresia in a regressed 1 ovary, (B) residual (unovulated) hydrated oocytes in a regenerating ovary, (C–F) late stage atresia (brown bodies; arrows). α = alpha atresia, β = beta atresia, RH = residual hydrated oocyte, EY = early yolked oocyte. The scale bars are 200 µm (black) and 100 µm (white).
Table 2.
Histological classification criteria for South Pacific albacore.
Figure 4.
Predicted trends in sex ratio (proportion male) with fork length (FL) and month.
Predictions derived from best fit model described in Table 3.
Table 3.
Parameter estimates from generalized linear mixed-effects models (GLMM).
Figure 5.
Observed gonad weight at fork length (FL) for male and female South Pacific albacore.
Data are presented by reproductive stage for females (but not males) and the regressing class includes classes 5, 6a and 6b (see Table 2). The curve plotted for females represents a gonad index of 1.7, above which individuals are assumed to be mature [27].
Figure 6.
Observed oocyte diameter and predicted trends with fork length (FL), month and oocyte stage.
Predictions derived from best fit model described in Table 3. Predicted oocyte diameter based on oocytes at stage 4 in upper panel and the month of November in lower panel. Data were available only for the peak spawning months of October, November and December.
Figure 7.
Gonad index and predicted trends with month and longitude for mature females and all males.
Predictions derived from best fit model described in Table 3.
Figure 8.
Proportion of development classes of mature female South Pacific albacore by month sampled.
Top panel represent fish sampled north of 25°S and bottom panel represents fish sampled south of 25°S. The regressing class includes classes 5, 6a and 6b (see Table 2). Sample size per month shown at top of each bar.
Figure 9.
Predicted trends in the proportion of active females with month for South Pacific albacore.
Top panel represent trends with fork length (FL) and bottom panel represents trends with age. Predictions derived from best fit model described in Table 3.
Figure 10.
Most advanced oocyte stage (upper) and postovulatory follicle stage (lower) at the time of death.
Most advanced oocyte (MAGO) stages are advanced yolked (3), migratory nucleus (4), and hydrated (5). POF stages are new (1), <12 hours (2), and >12 hours (3). POF = postovulatory follicle.
Figure 11.
Predicted trends in spawning fraction with fork length (FL), age and month.
Predictions derived from best fit model described in Table 3. No active females were sampled in September.
Figure 12.
Estimated batch fecundity and predicted trends with fork length (FL), age and month.
Predictions derived from best fit model described in Table 3.
Figure 13.
Estimated trends in potential monthly and annual fecundity with fork length (FL) and age.