Kulaw Dannielle H, Cowan James H, Jackson Melissa W
Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America.
Department of Marine Sciences, University of South Alabama, Mobile, Alabama, United States of America.
PLoS One. 2017 Mar 29;12(3):e0172360. doi: 10.1371/journal.pone.0172360. eCollection 2017.
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.
在相隔十年进行的研究中，我们提供了证据表明，墨西哥湾（海湾）近期出现了向性成熟进程放缓以及产卵量减少的转变，尤其是在年轻、体型较小的雌性红鲷鱼中。观察到成熟率降低（在年龄≤6岁的鱼类中）、性腺指数值较低以及产卵频率下降，且在墨西哥湾西北部尤为明显。此外，繁殖重要性指数显示，与前十年采样的同年龄组鱼类相比，近年来幼鱼（2至7岁）对产卵群体的贡献要少得多，而成年鱼（>8岁）的贡献则更多。与这些繁殖产出变化同时发生的是，整个海湾的捕捞压力稳步下降，产卵群体生物量和产卵潜力比率有所增加。因此，有可能红鲷鱼种群的年龄结构变得不那么截断，或者观察到的繁殖努力是由于2004年和2006年产生的近期强壮鱼群开始达到完全繁殖潜力的暂时影响。如果后者属实，在种群增长时期对该种群繁殖动态进行仔细记录，将在集合种群空间和十年时间尺度上提供新的认识。相比之下，如果前者属实，过度捕捞导致的截断年龄结构可能会限制墨西哥湾红鲷鱼种群的生产力。此外，我们了解到，在天然礁石和浅滩采集的墨西哥湾西北部红鲷鱼雌鱼的繁殖产出比以矗立和倒塌的石油和天然气平台形式存在的人工礁石上的雌鱼要高得多，因此，了解在这些不同栖息地发现的雌鱼的相对丰度，是朝着更好地理解影响该物种繁殖动态的因素迈出的重要下一步。
