Abstract

The carnivorous largemouth bass Micropterus salmoides has been introduced to many regions and poses a threat to native aquatic organisms due to predation, resulting in a significant decrease in biodiversity. Under conditions of prey scarcity, the largemouth bass is thought to consume smaller conspecifics. However, little is known about this species’ dietary reliance on intraspecific predation and its impact on the population structure. We investigated the length–frequency distribution of largemouth bass and estimated their reliance on intraspecific predation using stable carbon and nitrogen isotopes in an agricultural pond with no available prey fish. Almost all individual largemouth bass were collected via the pond drainage system. Within the largemouth bass population, the dominant length class was composed of fish measuring 100–160 mm standard length (SL), whereas few individuals measuring < 100 mm SL (first-year juveniles) were collected. The results from a Stable Isotope Analysis in R mixing model indicated that all four length classes (105–146, 165–180, 216–246, and 300–337 mm SL) of largemouth bass fed mainly on juvenile conspecifics and on red swamp crayfish (Procambarus clarkii). First-year juveniles could have been predated by other individuals of various sizes. The dominant 100–160 mm SL length class may have experienced a weak predation pressure when they were in the first-year juvenile class. Consequently, the largemouth bass population was unbalanced, with few first-year juveniles (< 100 mm SL) and dominance of a 100–160 mm SL length class.

摘要

肉食性大嘴鲈Micropterus salmoides已被引入许多地区，由于被捕食，对本地水生生物构成威胁，导致生物多样性大大减少。在猎物稀缺的条件下，大嘴鲈被认为消耗较小的物种。但是，关于该物种对种内捕食的饮食依赖性及其对种群结构的影响知之甚少。我们调查了大嘴鲈的频率分布，并估计了它们在没有可用猎物的农业池塘中使用稳定的碳和氮同位素对种内捕食的依赖。几乎所有大嘴鲈都是通过池塘排水系统收集的。在大嘴鲈鱼种群中，优势长度类别由尺寸为100–160的鱼组成 毫米标准长度（SL），而 收集到的个体<100毫米SL（第一年级少年）。R混合模型中的稳定同位素分析结果表明，大嘴鲈鱼的所有四种长度类别（105-146、165-180、216-246和300-337  mm SL）主要以幼鱼和红沼泽螯虾为食（克氏原螯虾）。第一年的少年可能早于其他各种规模的人。主要的100–160  mm SL长度班级在进入第一年级少年班时可能经历了较弱的掠食压力。因此，大嘴黑鲈种群不平衡，少有的第一年幼鱼（<100  mm SL），且优势在100-160  mm SL级别。