Impact of seasonal hydrological variation on tropical fish assemblages: abrupt shift following an extreme flood event

Abstract

Pulsing hydrology is a major factor affecting fish communities in tropical river‐floodplain ecosystems. Species responses to flow alteration are however poorly understood and are thus difficult to predict. Here, we investigated temporal changes in fish community structure (taxonomic and functional) in the Tonle Sap Lake, a floodplain ecosystem in Cambodia that supports the world largest inland fisheries and a UNESCO biosphere reserve. Fish catches were monitored daily at five locations around the lake between 2012 and 2015, with 53 species obtained over the course of the field study. Nine fish traits were recorded and used to characterize the functional composition of fish communities. Temporal changes in functional community structure in response to hydrological variation were assessed using multiple co‐inertia analysis (MCOA) and cross‐correlation function (CCF) approaches. Analyses revealed an abrupt shift in functional structure following extreme flood events in 2013 that included a marked decrease in large‐bodied fish at high trophic levels. Also observed were seasonal changes in the relative abundance of life‐history strategies, feeding habits, and accessory respiratory adaptations. Black fish (species that are relatively sedentary with an equilibrium‐type life‐history strategy) dominated during low‐water periods, whereas white fish (migratory species with opportunistic or periodic life‐history strategies) were dominant during high‐water periods. Dynamics of local assemblage structure were fairly synchronous spatially and were independent of the distance between locations. Species responses to the peak flood pulse were estimated to lag 1–2 months. Findings from this study indicate that management of fisheries resources in the Tonle Sap Lake should consider differential responses of species to hydrology as a function of life‐history strategies and other functional traits as well as factors that may influence time lags in population and community changes to extreme flow events.

Global change on the roof of the world: Vulnerability of Himalayan otter species to land use and climate alterations

“…Such outcomes are in keeping with the well‐known preference of the two species for moist forests (e.g., mangrove or peat swamp forests; Duplaix & Savage, 2018; Foster‐Turley, 1992; Gupta et al., 2020). Moreover, L. perspicillata and A. cinereus, respectively, feed on fish and invertebrates (i.e., crustaceans and shellfish; Anoop & Hussain, 2005; Duplaix & Savage, 2018; Foster‐Turley & Markowitz, 1982; Kanchanasaka & Duplaix, 2011), whose abundance in freshwater streams can be altered by scarce (i.e., drought) or extreme (i.e., floods) rainfall regimes (Chea et al., 2020; Gratwicke, 2004; Milner et al., 2013). This evidence further confirms the importance of precipitation‐related variables in shaping the distribution of these two species.…”

Relationships between Fish Communities and Habitat before and after a Typhoon Season in Tropical Mountain Streams

“…The overall differences measured in fish composition and habitat between the sites sampled in the pre-and post-typhoon seasons support the hypothesis that the relative strengths of biotic and abiotic mechanisms of community assembly can be regulated by the course of the intra-annual hydrologic variation. Although it has been well documented that catastrophic floods can seriously damage instream and riparian habitats and residential fish assemblages in mountain streams [50][51][52], the larger difference in fish compositions than habitat variables between the pre-and post-typhoon seasons implies that such an intra-annual hydrologic variation had a stronger direct impact on fish compared to the indirect influence through impacts on habitat. Although lotic fish communities have evolved with dynamic geomorphological conditions and are relatively resilient to extreme hydrologic events [53,54], severe floods may reduce fish presence, abundance, and influence community compositions [55].…”

Biến Động Theo Mùa Trong Cấu Trúc Phân Bố Quần Xã Tuyến Trùng Sống Tự Do Ở Sông Ba Lai, Tỉnh Bến Tre

“…Hệ thống sông Mê Kông có chế độ thủy văn chia làm hai mùa rõ rệt: Mùa lũ (mùa mưa) từ tháng 6 đến tháng 12 (với lưu lượng dòng chảy chiếm 70-80% tổng lưu lượng năm) và mùa cạn (mùa khô) từ tháng 1 đến tháng 5 [1]. Chính từ sự khác nhau trong đặc điểm thủy văn, tính chất môi trường lý -hóa giữa các mùa tác động rất lớn đến cấu trúc phân bố và đặc điểm quần xã thủy sinh vật như: động vật đáy không xương sống cỡ lớn [2]- [4], động vật có xương sống [5]- [7], phiêu sinh vật [8]- [10]. Tuy nhiên, nhóm động vật đáy không xương sống cỡ trung bình, vốn được xem là rất nhạy cảm và có vai trò quan trọng trong hệ sinh thái nền đáy [11]- [13], vẫn còn ít được chú ý trong các nghiên cứu về tác động của thay đổi mùa lên thủy sinh vật.…”