Taylor David L, Pearson Chloe, Green-Gavrielidis Lindsay, Hobbs Niels-Viggo, Thornber Carol, Cicchetti Giancarlo, Gerber-Williams Anna, McManus M Conor
Department of Marine Biology, Roger Williams University, One Old Ferry Road, Bristol, RI 02809.
Department of Biology and Biomedical Sciences, Salve Regina University, 100 Ochre Point Avenue, Newport, RI 02840.
Mar Ecol Prog Ser. 2023 Oct;720:133-159. doi: 10.3354/meps14409.
Juvenile black sea bass populations are increasing in southern New England estuaries of the northeastern United States with possible trophodynamic effects on native labrid species: tautog and cunner . In this study, we examined the abundance, size-structure, and feeding ecology of juvenile sea bass and labrids in Narragansett Bay (Rhode Island, USA) from June to October in 2018 and 2019, and evaluated potential interspecific competition using habitat, diet, and isotopic niche overlap indices. Juveniles (age-0+) of each fish species spatiotemporally co-occurred in shallow, polyhaline habitats throughout the estuary. Age-0 cohorts were numerically dominant across species and initially recruited to the study area in July (minimum total length, TL = 15-20 mm), reached peak abundances in mid- to late summer (maximum abundances = 12-140 fish 100 m), and emigrated from field sites in October (maximum TL = 85-96 mm). Stomach content and stable isotope (δN and δC) analyses determined that focal fishes were generalist carnivores that foraged in bentho-pelagic food webs. Focal fishes also overlapped in their respective ambit and core isotopic niche space, but interspecific dietary overlap was size-dependent. Dietary overlap was most pronounced between sea bass ≤ 49 mm TL and labrids ≤ 59 mm TL due to their mutual reliance on gammarid and caprellid amphipods. Ontogenetic dietary shifts then resulted in food niche segregation, such that sea bass 50-139 mm TL consumed decapod crustaceans and fish, whereas labrids 60-181 mm TL mainly fed on amphipods, worms, bivalves, and turf-associated biota, i.e. bryozoans, hydroids, and seaweeds. Habitat and trophic niche overlap between early juvenile sea bass and labrids have not caused opposite population trajectories or food resource limitation in Narragansett Bay, indicating an absence of exploitative competition. Alternatively, realized competition in focal fishes may be too spatiotemporally restricted to alter their population dynamics. Continuous monitoring of the sea bass's bio-ecological effects in southern New England estuaries is warranted, however, given their recent range expansion and increasing abundances at northern latitudes.
美国东北部新英格兰南部河口的幼年黑海鲈数量正在增加，这可能对当地的隆头鱼科物种（黑口新虾虎鱼和康氏小公鱼）产生营养动力学影响。在本研究中，我们于2018年和2019年6月至10月调查了美国罗德岛纳拉甘西特湾幼年海鲈和隆头鱼科鱼类的丰度、大小结构和摄食生态，并使用栖息地、饮食和同位素生态位重叠指数评估了潜在的种间竞争。每种鱼类的幼鱼（0龄以上）在整个河口的浅海、多盐度栖息地中在时空上同时出现。0龄群体在所有物种中数量占主导地位，7月开始进入研究区域（最小全长，TL = 15 - 20毫米），夏末达到丰度峰值（最大丰度 = 12 - 140尾鱼/100平方米），10月从野外站点迁出（最大TL = 85 - 96毫米）。胃内容物和稳定同位素（δN和δC）分析表明，目标鱼类是在底栖 - 浮游食物网中觅食的广食性肉食动物。目标鱼类在各自的活动范围和核心同位素生态位空间也有重叠，但种间饮食重叠与大小有关。由于它们都依赖于钩虾和麦秆虫等端足类动物，TL≤49毫米的海鲈和TL≤59毫米的隆头鱼科鱼类之间的饮食重叠最为明显。个体发育过程中的饮食转变导致了食物生态位的分离，因此TL为50 - 139毫米的海鲈以十足目甲壳类动物和鱼类为食，而TL为60 - 181毫米的隆头鱼科鱼类主要以端足类动物、蠕虫、双壳类动物以及与草皮相关的生物群（即苔藓虫、水螅虫和海藻）为食。幼年海鲈和隆头鱼科鱼类在栖息地和营养生态位上的重叠并没有导致纳拉甘西特湾相反的种群动态轨迹或食物资源限制，这表明不存在剥削性竞争。另外，目标鱼类之间实际发生的竞争在时空上可能受到太大限制，以至于无法改变它们的种群动态。然而，鉴于黑海鲈最近在范围上的扩展以及在北纬地区数量的增加，有必要持续监测其在美国新英格兰南部河口的生物生态影响。
