Blanco-Martínez Zeferino, Pérez-Castañeda Roberto, Sánchez-Martínez Jesús Genaro, Benavides-González Flaviano, Rábago-Castro Jaime Luis, Vázquez-Sauceda María de la Luz, Garrido-Olvera Lorena
Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Tamaulipas, Victoria, Tamaulipas, Mexico.
Instituto de Ecología Aplicada, Universidad Autónoma de Tamaulipas, Victoria, Tamaulipas, Mexico.
PeerJ. 2020 Dec 8;8:e10496. doi: 10.7717/peerj.10496. eCollection 2020.
Seagrasses are critical habitats for the recruitment and growth of juvenile penaeid shrimps within estuaries and coastal lagoons. The location of a seagrass bed within the lagoon can determine the value of a particular bed for shrimp populations. Consequently, differences in the abundance of shrimp can be found in seagrasses depending on their location. As shrimp density increases, density-dependent effects on biological parameters are more likely to occur. However, knowledge about density-dependent processes on shrimp populations in nursery habitats remains limited. The present investigation was undertaken to examine the effects of population density on shrimp condition in two selected seagrass beds, located at different distance from a tidal inlet, one 25 km away (distant) and the other 1 km away (nearby), in a subtropical coastal lagoon. The study was based on monthly samplings during one year in Laguna Madre (Mexico), performing a total of 36 shrimp trawls (100 m each one) within each seagrass bed ( = 3 trawls per bed per month for 12 months). Shrimp density was related to the proximity to the tidal inlet (higher density was consistently observed in the nearby seagrass bed), which in turn adversely affected the condition of both species studied ( and ). In this regard, the present study provides the first evidence of density-dependent effects on shrimp condition inhabiting a nursery habitat. Both shrimp species exhibited a negative relationship between condition and shrimp density. However, this pattern differed depending on the proximity to the tidal inlet, suggesting that shrimp populations inhabiting the nearby seagrass bed are exposed to density-dependent effects on condition; whereas, such effects were not detected in the distant seagrass bed. Shrimp density within the distant seagrass bed was probably below carrying capacity, which is suggested by the better shrimp condition observed in that area of the lagoon. Intra and interspecific competition for food items is surmised to occur, predominantly within seagrass beds near the tidal inlet. However, this hypothesis needs to be tested in future studies.
海草床是河口和沿海泻湖内对虾幼体的招募和生长至关重要的栖息地。泻湖内海草床的位置能够决定某一特定海草床对于虾类种群的价值。因此，根据海草床的位置不同，虾类的丰度也会有所差异。随着虾类密度的增加，对生物学参数的密度依赖性效应更有可能发生。然而，关于育苗栖息地中虾类种群的密度依赖性过程的知识仍然有限。本次调查旨在研究种群密度对位于亚热带沿海泻湖、距潮汐入口不同距离（一个距离为25公里（远），另一个距离为1公里（近））的两个选定海草床中虾类状况的影响。该研究基于在墨西哥马德雷泻湖进行的为期一年的月度采样工作，在每个海草床内总共进行了36次虾类拖网捕捞（每次拖网100米）（即每个海草床每月拖网3次，共12个月）。虾类密度与距潮汐入口的距离有关（在较近的海草床中始终观察到更高的密度），这反过来又对所研究的两种虾类的状况产生了不利影响（和）。在这方面，本研究首次提供了密度依赖性效应影响育苗栖息地中虾类状况的证据。两种虾类的状况与虾类密度之间均呈现负相关关系。然而，这种模式因距潮汐入口的距离而异，这表明栖息在较近海草床中的虾类种群受到了密度依赖性的状况影响；而在较远的海草床中未检测到此类影响。较远海草床内的虾类密度可能低于承载能力，这从该泻湖区域观察到的较好的虾类状况可以推断出来。据推测，食物的种内和种间竞争主要发生在潮汐入口附近的海草床内。然而，这一假设需要在未来的研究中进行验证。
