Hodgson Olivia C, Stark Sydney, Schall Megan K, Smith Geoffrey D, Smalling Kelly L, Wagner Tyler
Pennsylvania Cooperative Fish and Wildlife Research Unit, The Pennsylvania State University, University Park, Pennsylvania, USA.
Department of Biology, Pennsylvania State University Hazleton, Hazleton, Pennsylvania, USA.
Ecology. 2025 Sep;106(9):e70180. doi: 10.1002/ecy.70180.
Invasive species are drivers of ecological change with the potential to reshape the structure and function of terrestrial and aquatic ecosystems. The invasive flathead catfish (Pylodictis olivaris) is an opportunistic predator that has established a rapidly growing population in the Susquehanna River, Pennsylvania, USA, since they were first detected in 2002. Although the predatory effects of invasive catfishes on native fish communities have been documented, the effects of invasion on riverine food webs are poorly understood. This study quantified the effects of invasive flathead catfish on the trophic position (TP) and isotopic niche of the river's food web by comparing invaded and non-invaded sites. In addition to flathead catfish, the food web components examined included crayfish, minnows, and two ecologically and socioeconomically important fish species: the smallmouth bass (Micropterus dolomieu) and channel catfish (Ictalurus punctatus). We found that flathead catfish occupied the highest TP, with a posterior mean TP of 3.08 (95% credible interval = [2.71, 3.42]), exceeding that of the two resident fish predators, the smallmouth bass and channel catfish. The TP of the resident channel catfish, which occupies a similar ecological niche, declined after flathead catfish invasion. In fact, there was a 0.92 posterior probability that channel catfish TP was lower in invaded sites than at non-invaded sites. Using a Bayesian bivariate ellipses analysis, we found overwhelming evidence of isotopic niche expansion and overlap for all components of the food web in the presence of flathead catfish. These findings support the "trophic disruption hypothesis," where an introduced species prompts resident species to change diets in an attempt to avoid competition and predation following invasion. Our results indicate that flathead catfish invasion is altering food web structure and energy flow in a large riverine ecosystem and contributes to the breadth of knowledge regarding how ecosystems may respond to the introduction of a large predatory fish species.
入侵物种是生态变化的驱动因素，有可能重塑陆地和水生生态系统的结构与功能。入侵性的扁头鲶鱼（Pylodictis olivaris）是一种机会主义捕食者，自2002年首次在美国宾夕法尼亚州的萨斯奎哈纳河被发现以来，其种群数量迅速增长。尽管入侵鲶鱼对本地鱼类群落的捕食影响已有记录，但入侵对河流食物网的影响却知之甚少。本研究通过比较入侵和未入侵的地点，量化了入侵扁头鲶鱼对河流食物网营养级位置（TP）和同位素生态位的影响。除了扁头鲶鱼，所研究的食物网组成部分还包括小龙虾、米诺鱼，以及两种在生态和社会经济方面都很重要的鱼类：小口黑鲈（Micropterus dolomieu）和沟鲶（Ictalurus punctatus）。我们发现扁头鲶鱼占据最高的营养级位置，其后验平均营养级位置为3.08（95%可信区间 = [2.71, 3.42]），超过了两种本地鱼类捕食者小口黑鲈和沟鲶。占据相似生态位的本地沟鲶的营养级位置在扁头鲶鱼入侵后下降。事实上，有0.92的后验概率表明，入侵地点的沟鲶营养级位置低于未入侵地点。通过贝叶斯双变量椭圆分析，我们发现有压倒性的证据表明，在有扁头鲶鱼存在的情况下，食物网的所有组成部分都出现了同位素生态位扩展和重叠。这些发现支持了“营养级破坏假说”，即引入物种促使本地物种改变饮食，以试图在入侵后避免竞争和捕食。我们的结果表明，扁头鲶鱼的入侵正在改变大型河流生态系统中的食物网结构和能量流动，并有助于拓宽关于生态系统如何应对大型掠食性鱼类物种引入的知识广度。
