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
Estimates of age and growth of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna remain problematic because validation of growth zone deposition (opaque and translucent) has not been properly evaluated. Otolith growth structure (zone clarity) can be poorly defined for tropical tunas, but the use of bomb radiocarbon dating has validated age estimates to 16–18 years for yellowfin and bigeye tuna. Use of the radiocarbon decline period — defined by regional coral and otoliths — provided valid ages through ontogeny. Yellowfin tuna aged 2–18 years (n = 34, 1029–1810 mm FL) and bigeye tuna aged 3–17 years (n = 12, 1280–1750 mm FL) led to birth years that were coincident with the bomb radiocarbon decline. The results indicate there was no age reading bias for yellowfin tuna and that age estimates of previous studies were likely underestimated for both species.
The fecundity of Gray Triggerfish Balistes capriscus has been difficult to estimate, as few imminently spawning or recently spawned females have been detected. Our study focused on verifying the pattern of oogenesis and fecundity type in Gray Triggerfish. During 1999–2012, females (n = 1,092) were collected from the eastern Gulf of Mexico, and subsets of these fish were used to calculate condition indices and assess ovarian histology. The gonadosomatic index, hepatosomatic index, and Fulton's condition factor indicated that liver and somatic energy stores increased prior to spawning and were depleted throughout the spawning period, characteristic of a capital pattern of energy storage and allocation to reproduction. Typical of a capital breeding pattern, we also observed (1) a hiatus in oocyte size distribution and (2) group‐synchronous oogenesis, which are both traits of a determinate fecundity type. However, evidence that fecundity was not set prior to spawning included the observation of “de novo” vitellogenesis during the spawning season; secondary oocytes increased in number and failed to increase in mean size over time. Thus, Gray Triggerfish exhibit an indeterminate fecundity type with mixed reproductive traits that may characterize species exhibiting female parental care in warmwater environments. Further, we estimated the secondary oocyte growth rate (37 m/d) based upon the time lag of postovulatory follicle (POF) degeneration. Using oocyte growth rate and the proportion of females bearing POFs, the interspawning interval was estimated to range from 8 to 11 d, indicating that 8–11 batches/female could be produced during the estimated 86‐d reproductive period. The hiatus in oocyte size distribution was used to define a minimum size (250 m) from which to distinguish an advancing batch of secondary growth oocytes. Batch fecundity (BF) ranged from 0.34 to 1.99 million eggs and was significantly related to FL (mm): BF = 8,703.69·FL – 1,776,483 (r2 = 0.56). Received October 10, 2014; accepted June 27, 2015
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.