Maturation of female common snook Centropomus undecimalis: implications for managing protandrous fishes

Abstract

The assumption for hermaphroditic fish species that mature individuals of the terminal sex arise directly from mature individuals of the primary sex has led to the use of sex ratios as a proxy for age at maturity (A 50). The timing of transition and deficient energy reserves, however, can result in a delay between transition and spawning. To test the assumption of female maturity and investigate the relationship between maturation and energy reserves, common snook, Centropomus undecimalis, a protandrous hermaphrodite, were collected from rivers, estuaries, inlets and offshore habitats on the east coast of Florida during 2010-2015. Immature females were observed every month, with lowest proportions during the peak spawning months of July and August. When calculated based on sex ratio, A 50 (8.1 years) overestimated the age at which 50% of the female population was, in fact, mature (4.1-4.9 years). Best-fit models indicate that mesenteric fat index (I F) and hepato-somatic index (I H) were significantly affected by gonad phase, month and size and weakly by habitat. In post hoc analysis, immature female I F did not differ significantly from developing and regenerating females, but immature female I H was significantly lower than that for all mature phases except animals in the regressing phase. Although immature females may have sufficient energy in terms of fat, it appears that energy is not allocated to reproductive processes, as evidenced by lower I H. Nonetheless, approximately 95% of females were spawning-capable during peak spawning months, suggesting that the energy threshold at which immature females reach maturity is met by most females each spawning cycle.

Cascading effects of climate change on recreational marine flats fishes and fisheries

“…The extent to which fish may be capable of adapting behaviorally and physiologically to the rate of changing water conditions due to climate change is generally not well known and a key determinant of the degree to which climate change will impact their energetics, and more broadly, their populations. There is also often a complex relationship between fish energetics and life history traits including maturation and reproductive output (e.g., Young et al 2020 ), which will influence how changes in energetics may result in altered population dynamics for flats fishes. Although the degree to which changing ocean conditions will impact flats fishes is not totally clear, given they live in such thermally extreme shallow coastal habitats, often near thermal maxima, it certainly allows for potential to have negative impacts on their bioenergetics, which in turn may influence individual fitness and population dynamics.…”

Primed and cued: long-term acoustic telemetry links interannual and seasonal variations in freshwater flows to the spawning migrations of Common Snook in the Florida Everglades

“…This period was selected based both on its role in the sexual maturation of Snook, and as a period shown to provide enhanced opportunities for foraging on freshwater prey as water levels drops through the dry season [ 38 , 46 , 47 ]. Snook are protandrous hermaphrodites, transitioning from mature males to females at sizes that range from a total length (TL) of 264 to 876 mm [ 57 , 94 ]. Histological analysis of female Snook indicated that the months between spawning periods correspond to the development and regeneration of oocytes, and high hepato-somatic indices suggest that sex transition and maturation is occurring outside of the spawning season [ 57 ].…”

“…Snook are protandrous hermaphrodites, transitioning from mature males to females at sizes that range from a total length (TL) of 264 to 876 mm [ 57 , 94 ]. Histological analysis of female Snook indicated that the months between spawning periods correspond to the development and regeneration of oocytes, and high hepato-somatic indices suggest that sex transition and maturation is occurring outside of the spawning season [ 57 ]. Because gametogenesis and reproductive migrations are energetically costly, resource acquisition during this period can be particularly important.…”

“…Because gametogenesis and reproductive migrations are energetically costly, resource acquisition during this period can be particularly important. Results from Young et al [ 57 ] support capital breeding to some extent for Snook, and that energy derived outside of the spawning season is used during reproduction [ 95 ]. Because the timing of peak prey concentration can vary widely from year-to-year based on the annual hydrograph (Additional file 1 : Fig.…”

Reproductive biology of the fat snook Centropomus parallelus Poey, 1860 (Teleostei, Centropomidae) and implications for its management in the southern Atlantic Ocean

“…Even though fat snook individuals first mature as males, and then undergo a sex change to become secondary females, few immature females were registered, and we found no evidence (residual male tissue) that they derived from post‐spawning males. The occurrence of few immature females was also recorded in southern (Chaves & Nogueira, 2019) and south‐eastern Brazil (Santos, 2014), and this fact is also known for C. undecimalis (Young et al ., 2020). Our understanding on the evolutionary drivers and advantages underlying the sequential hermaphroditism strategy is still very limited, but the dominant explanation for male‐to‐female sex change (protandry), the size‐advantage model (Warner, 1975), suggests that males switch sex to females because large females achieve a greater fitness, as female fecundity and reproductive energy increase with body size (Barneche et al ., 2018).…”