Estimating the Dependence of Spawning Frequency on Size and Age in Gulf of Mexico Red Snapper

Abstract

In 2011, a large multivessel survey was conducted to provide nearly synoptic sampling of Red Snapper Lutjanus campechanus throughout their reproductive season in the U.S. Gulf of Mexico. A total of 2,487 Red Snapper were caught with a female : male ratio that was approximately 1:1. The ovaries of 1,002 females were histologically examined. Females (n = 391) were found with spawning markers (postovulatory follicles and hydrated oocytes) throughout the study area, but primarily in outer shelf waters. Statistical models were developed to quantify and test the dependence of the proportion of females bearing spawning markers (spawning fraction) on female length and age, time of year, depth, gear type (vertical line or longline), or region (east or west of the Mississippi River). Most of the variance in spawning fraction was explained by the time of year; spawning fractions were generally low in spring, peaked in midsummer, and declined by fall. There was also strong statistical evidence of a positive relationship between spawning fraction and either age or length. The effects of region and gear type were not significant once time of year and size or age were accounted for. These results demonstrate the need to account for differences in the time of year and age structure of the population when the productivity of populations of Red Snapper are compared. For example, productivity has been hypothesized to be greater in the western Gulf than in the eastern Gulf, as evidenced by regional patterns of egg and larval abundance. Our results suggest that this regional difference is not due to any intrinsic difference in the biology of the fish, but simply a consequence of there being more large, old Red Snapper in the western Gulf. Recent stock assessments have indicated that Red Snapper are increasing in abundance and there is a need to continue monitoring to detect any possible compensation in reproduction. Received November 25, 2014; accepted April 2, 2015

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

“…This reinforces the hypothesis that Red Snapper in the western Gulf may have more varied reproductive potential than fish in the northern Gulf (Lyczkowski‐Shultz and Hanisko ; Porch et al. ).…”

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

“…A potential regional difference in SF detected during the recovery period indicated eastern red snapper spawned slightly more often than conspecifics in the west. While this result contradicts reports that spawning frequency for red snapper is greater in the western Gulf due to the existence of larger fish in that region [20], and our findings corroborate those of Porch et al [20], who found no regional difference in spawning frequency east or west of the Mississippi was found once age or size was considered.…”

“…To account for variability in SF estimates caused by the time of day when fish were caught [45] or other factors including accelerated degradation of POFs at warm water temperatures [72], we chose to rely on SF estimates determined using the TC method in this study; this is likely the most accurate method for determining SF because it is inclusive to both day-0 and day-1 fish [34, 48], each of which are known histological spawning indicators [20]. A temporal trend toward less frequent spawning in recent years was observed.…”

“…Smaller sample sizes [40] and reduced size and age ranges during the recovery period may account for some of these differences, as SF is known to increase with maternal size and age in iteroparous fishes [11, 34, 57, 73–75], including red snapper [20]. On the other hand, while no studies to date have directly linked fishing pressure to changes in spawning frequency, stocks with a severely truncated age distribution are dependent upon small, younger spawners [17], which have been shown to spawn less often and over a shorter seasonal duration compared to older, larger fish [5, 20, 74, 76]. A potential regional difference in SF detected during the recovery period indicated eastern red snapper spawned slightly more often than conspecifics in the west.…”

A Comparison of Fish Community Structure at Mesophotic Artificial Reefs and Natural Banks in the Western Gulf of Mexico

“…This inference is supported by a recent survey of recreational anglers in Texas, which suggested that over 70% of the anglers used artificial reefs, with nearly 40% of these anglers targeting standing platforms (Schuett et al 2015). Moreover, in a GOM-wide study, Porch et al (2015) observed the highest Red Snapper spawning frequencies at natural habitats in our region, further highlighting the potential benefits of the RTR artificial reefs and the diversion of fishing pressure away from natural habitats. Although more detailed study of fishing effort among habitat types is needed, these findings certainly reveal several management implications for RTR habitats versus natural banks.…”