Sex‐Specific Growth and Reproductive Dynamics of Red Drum in the Northern Gulf of Mexico

Abstract

The Red Drum Sciaenops ocellatus stock is heavily targeted in the Gulf of Mexico (GOM) by recreational fishers and supports a small commercial fishery in Mississippi. Despite their popularity, little recent work has been done to describe their life history. In this work, we describe sex‐specific growth and reproductive dynamics of Red Drum collected from the northern GOM from September 2016 through October 2017. We evaluated seven candidate growth models and found that the three‐parameter von Bertalanffy growth function (VBGF) was the best candidate length‐at‐age model. No significant difference in growth between sexes was observed with the three‐parameter VBGF, despite the female‐specific curve having a larger mean asymptotic length than the male‐specific curve. All seven candidate growth models predicted similar mean length‐at‐age estimates, and four of them exhibited significant differences in sex‐specific mean length at age, with females reaching a larger length at age than males after age 5. There was no significant difference between the sex‐specific weight‐at‐length relationships. Red Drum are batch spawners that spawn in northern GOM coastal waters during August and September. We estimated 3.7 d between spawns and 10.5 spawning events per female in 2017. Nearly 20% of fish collected during the spawning season were sexually mature but reproductively inactive, indicating the possibility of skipped spawning. The age at 50% maturity was around 3 years (length at 50% maturity = 670 mm TL) in both sexes, but fish were not spawning capable until age 4.5 (703 mm TL) in males and age 5.8 (840 mm TL) in females. Furthermore, elevated gonadosomatic indices were not observed until around age 5–6. The updated life history information presented in this work helps to address current data limitations and provides critical information for future assessments of Red Drum stocks in the northern GOM.

Rapid changes in age structure, mortality, and escapement accompanied stock recovery of the estuarine Red Drum population of Texas

“…The GLM comparing TL to age, sex, and season suggested that age and season were explanatory, whereas sex and the age × sex interaction were not (Table 1). These results were consistent with previous studies suggesting that growth trajectories change significantly after age 4 (Ross et al 1995), thus hindering mathematical modeling of growth in Red Drum across a broader range of ages with a simple single‐stage growth function (Ross et al 1995; Porch et al 2001; Bennetts et al 2019). For this reason, we used only age‐4 and younger individuals for subsequent analyses, which nevertheless constituted the bulk of the observed estuarine population.…”

“…A singular sex‐aggregated growth trajectory was assumed if the likelihood ratio for inclusion of the age × sex term did not significantly improve the model. Although sex‐based differences in growth have been observed in Red Drum, these differences typically manifest after sexual maturity, and aggregated growth functions perform reasonably well in age‐classes younger than 5 (Bennetts et al 2019; Hightower et al 2022). Upon observation of no growth differences between sexes for ages 0–4 (see Results), sex‐aggregated point estimates of mean length at age were obtained from otolith‐aged individuals that were collected in each season (i.e., seasonal mean length at age).…”

Reproductive strategies of a temperate Australian sciaenid (teraglin, Atractoscion atelodus )

“…There are a few examples of sciaenids where males and females mature at similar sizes (e.g. S. ocellatus , Bennetts et al., 2019) and further research into exploring the possible mechanisms for these differing life history strategies is warranted.…”

“…ocellatus, Bennetts et al, 2019) and further research into exploring the possible mechanisms for these differing life history strategies is warranted.…”

Accuracy of histology, endoscopy, ultrasonography, and plasma sex steroids in describing the population reproductive structure of hatchery‐origin and wild white sturgeon

“…Despite the presence of precocious cysts, the males sampled in this study were considered functionally immature (prepubertal) as they did not have enough spermatozoa in the testes to successfully fertilize eggs. However, they would be considered physiologically mature (post-pubertal) based on the literature (see Bennetts et al, 2019;Lowerre-Barbiere et al, 2016). To our knowledge, precocious cysts within the gonad in a highly advanced stage of gonadal development have not been described in the literature for any sturgeon or teleost species.…”