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Seasonality in diet and feeding habits of the endemic Chala tilapia (Oreochromis hunteri) and two introduced tilapiine cichlids in Lake Chala, East Africa
Hydrobiologia ( IF 2.6 ) Pub Date : 2020-10-08 , DOI: 10.1007/s10750-020-04427-3
Jorunn Dieleman , Christine Cocquyt , Wanja Dorothy Nyingi , Dirk Verschuren

Oreochromis cf. korogwe and Coptodon rendalli, two tilapiine fishes introduced to Lake Chala (Kenya/Tanzania) ~ 40 years ago, may negatively affect the endemic Chala tilapia (Oreochromis hunteri) by competition for food. However, the actual threat posed by the introduced cichlids cannot be assessed without data on the local feeding habits of all three species. This paper describes the diet of O. hunteri and both introduced species, focusing on seasonal changes in food-source availability. Microscopic analysis of gut content in 35 fishes collected over a 20-month period was compared with the composition of littoral food sources and seasonal variation in the limnetic phytoplankton and complemented with exploratory stable-isotope analysis of fish tissue. We found that all three tilapiines in Lake Chala are herbivorous, and during most of the year, they feed on algae and organic detritus on and between rocks in the littoral zone. However, in July–September they migrate to open water to feed on blooming phytoplankton. Interspecific differences in gut content and stable-isotope composition suggest that O. hunteri may have a competitive advantage over the two newcomers by making better use of this seasonal extra food resource. However, this advantage may erode when continuing climate change starts affecting the bloom’s predictability.

中文翻译:

东非查拉湖特有的查拉罗非鱼 (Oreochromis Hunteri) 和两种引进的罗非鱼慈鲷的饮食和摄食习惯的季节性

Oreochromis 参见。korogwe 和 Coptodon rendalli 是大约 40 年前引入查拉湖(肯尼亚/坦桑尼亚)的两种罗非鱼,可能通过食物竞争对地方性查拉罗非鱼(Oreochromis Hunti)产生负面影响。然而,如果没有关于所有三个物种当地食性的数据,就无法评估引入的慈鲷造成的实际威胁。本文描述了 O.hunteri 和两个引入物种的饮食,重点关注食物来源可用性的季节性变化。对 20 个月内收集的 35 条鱼的肠道内容进行显微镜分析,将其与沿海食物来源的组成和湖沼浮游植物的季节性变化进行比较,并辅以鱼组织的探索性稳定同位素分析。我们发现查拉湖中的所有三种罗非鱼都是草食性的,并且在一年中的大部分时间里,它们以沿海地区岩石上和岩石之间的藻类和有机碎屑为食。然而,在 7 月至 9 月,它们迁移到开阔水域,以盛开的浮游植物为食。肠道含量和稳定同位素组成的种间差异表明,通过更好地利用这种季节性的额外食物资源,O.hunteri 可能比这两个新来者具有竞争优势。然而,当持续的气候变化开始影响开花的可预测性时,这种优势可能会消失。通过更好地利用这种季节性的额外食物资源,hunteri 可能比这两个新来者具有竞争优势。然而,当持续的气候变化开始影响开花的可预测性时,这种优势可能会消失。通过更好地利用这种季节性的额外食物资源,hunteri 可能比这两个新来者具有竞争优势。然而,当持续的气候变化开始影响开花的可预测性时,这种优势可能会消失。
更新日期:2020-10-08
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