Temporal and spatial comparisons of the reproductive biology of northern Gulf of Mexico (USA) red snapper (Lutjanus campechanus) collected a decade apart

Abstract

In studies done a decade apart, we provide evidence of a recent shift toward a slower progression to sexual maturity as well as reduced egg production, especially among young, small female red snapper, in the Gulf of Mexico (Gulf). Slower maturation rates (among fish ≤6 years old), lower GSI values and decreased spawning frequency were observed, and were especially pronounced in the northwestern Gulf. Furthermore, an Index of Reproductive Importance showed that young fish (ages 2–7) are contributing far less to the spawning stock in recent years, while older fish (>8 years) are contributing more, when compared to fish from the same age groups sampled in the previous decade. Coincident with these changes in reproductive output, fishing pressure has steadily declined gulf-wide, and spawning stock biomass and spawning potential ratio have increased. Thus, it is possible that the age structure of the red snapper stock is becoming less truncated, or that reproductive effort observed is due to the temporary influence of recent strong year classes produced in 2004 and 2006 as they begin to reach full reproductive potential. If the latter is true, careful documentation of the stock’s reproductive dynamics during a time of population growth provides new understanding at the meta-population spatial and decadal temporal scales. In contrast, if the former is true, a truncated age structure due to overharvest can limit the productivity of the Gulf red snapper stock. In addition, we have learned that red snapper females in the northwestern Gulf collected on natural reefs and banks have much higher reproductive output than those on artificial reefs in the form of standing and toppled oil and gas platforms, thus making the need to know the relative abundance of females found on these disparate habitats an important next step toward better-understanding factors impacting the reproductive dynamics of this species.

Habitat‐Specific Reproductive Potential of Red Snapper: A Comparison of Artificial and Natural Reefs in the Western Gulf of Mexico

“…; Kulaw et al. ). Additionally, some differences in reproduction, including GSI, SFE, and batch fecundity (BFE), were found among six geographical regions spanning the northern Gulf from central Florida to south Texas (Kulaw ).…”

“…Previous studies of Red Snapper reproduction in the Gulf have been focused offshore of Alabama and Louisiana (Collins et al 2001;Woods et al 2003;Jackson et al 2006Jackson et al , 2007Kulaw 2012;Glenn et al 2017), Florida (Brown-Peterson et al 2008, and the Yucatán Peninsula (Brulé et al 2010). Off Louisiana, differences in gonadosomatic index (GSI), maturity, and spawning frequency (SFE) were found among natural shelf-edge banks, standing platform sites, and toppled platform sites; however, due to geographical constraints, these habitats were located across a wide depth range (i.e., 55-160 m;Kulaw 2012;Glenn et al 2017;Kulaw et al 2017). Additionally, some differences in reproduction, including GSI, SFE, and batch fecundity (BFE), were found among six geographical regions spanning the northern Gulf from central Florida to south Texas (Kulaw 2012).…”

Effects of a New Artificial Reef Complex on Red Snapper and the Associated Fish Community: an Evaluation Using a Before–After Control–Impact Approach

“…Based on the ages of Red Snapper collected in this study and the reported age at 50% maturity of 4.5 years for Red Snapper in the western GOM (Gallaway et al 2009;Kulaw et al 2017), a vast majority of individuals inhabiting CCNR were juveniles. An ontogenetic habitat shift has been suggested for Red Snapper, and juveniles can move from lowrelief shell rubble habitats to intermediate-relief structures within the first year (Wells et al 2008c;Gallaway et al 2009).…”

Using Common Age Units to Communicate the Relative Catch of Red Snapper in Recreational, Commercial, and Shrimp Fisheries in the Gulf of Mexico

“…Red Snapper become reproductively mature between 2 and 8 years of age, with apparent individual variation through time and across regions (Kulaw et al. ). During this period, Red Snapper continue to occupy high‐relief habitat, spanning the width of the continental shelf, with larger individuals shifting to reefs with increasing vertical height and complexity.…”

“…Given that this ontogenetic shift appears to be related to the increasing body size of Red Snapper precluding them from sheltering in shell rubble, the snapper that do not recruit to highrelief habitats are likely subject to predation. Red Snapper become reproductively mature between 2 and 8 years of age, with apparent individual variation through time and across regions (Kulaw et al 2017). During this period, Red Snapper continue to occupy high-relief habitat, spanning the width of the continental shelf, with larger individuals shifting to reefs with increasing vertical height and complexity.…”