Fishing down or fishing up in Chinese freshwater lakes

Abstract

Changes in mean trophic level (MTL) of catches have been widely used to reflect the impact of industrial fisheries on aquatic ecosystems because this measure represents the relative abundance of fished species across the trophic level spectrum. In this study, fisheries data from six important freshwater lakes at the middle-lower Yangtze River and Huaihe River reach of Southern China from 1949 to 2009 were used to evaluate changes in catch MTL. After fishery markets opened at 1985, fish catches increased significantly in all the lakes. Lakes Poyang and Dongting, which were dominated by omnivores and connected to the Yangtze River, showed no significant change in catch MTL before and after 1985. Catch MTL in lakes Taihu and Hongze increased significantly due to an increase in the proportion of pelagic zooplanktivorous. Catches in Lake Chaohu were dominated by zooplankton-feeding lake anchovy, Coilia ectenes Temminck & Schlegel and icefish, Neosalanx taihuensis Chen, while Lake Donghu was dominated by phytoplanktivorous carps. Due to low biodiversity, catch MTL of these two lakes showed no significant change before and after 1985. Both fisheries-based and human activities-based drivers influenced the structure and catch MTL of fisheries in Chinese freshwater lakes.

Should I stay or should I go? Fishers’ ability and willingness to adapt to environmental change in Cambodia's Tonle Sap Lake

“…Limburg and Waldman () suggested direct fixes, such as removing dams, wherever possible. Making artificial fish habitats, releasing juveniles from artificial hatcheries, cracking down on illegal fishing and increasing protection boundaries have also been suggested to combat global fish decline (Wang et al., ). Using less damaging fishing gears, establishing closed and open seasons and limiting harvests are also possible alternatives (Wang et al., ).…”

“…() listed five main reasons for the decline: overexploitation, pollution, changes in water flow, habitat destruction and the introduction of invasive species. Land drainage, eutrophication, dam construction, overfishing, pollution and climate change have also been described as contributing to fish decline (Limburg & Waldman, ; Wang, Xu, Yu & Lei, ). Areas that depend on naturally changing flow patterns, such as Tonle Sap Lake, are particularly vulnerable to anthropogenic changes like dam construction or forest destruction that affects water retention and run‐off (Dudgeon et al., ).…”

“…Making artificial fish habitats, releasing juveniles from artificial hatcheries, cracking down on illegal fishing and increasing protection boundaries have also been suggested to combat global fish decline (Wang et al., ). Using less damaging fishing gears, establishing closed and open seasons and limiting harvests are also possible alternatives (Wang et al., ). Protecting areas during breeding seasons is also a possible solution, although this may favour fish with short breeding seasons and not directly benefit those with longer breeding seasons (Chen, Li & Wang, ).…”

Trophic Niche Width and Overlap of Three Benthic Living Fish Species in Poyang Lake: a Stable Isotope Approach

“…Plants were relatively easy to acquire since Poyang Lake was rich in vegetation (You et al 2015), SEA of C. auratus was smallest among these benthic fishes as consumers tended to specialize and narrow their trophic niches when high resource availability presence (Rossi et al 2015). Due to heavy fishing pressure in Poyang Lake (Wang et al 2014), even small fish were capture by local fish men, the predator S. asotus might be short of food sources. As a result, its diet was broadened, and had the largest trophic niche width (SEA) in both northern and southern parts (Table 4).…”

Fishing down then up the food web of an invaded lake

“…Despite high exploitation pressure of some freshwater fisheries, fishing down the food web does not appear to be occurring as widely in these systems. For example, 5 shallow eutrophic freshwater lakes in China, known to be heavily polluted and impacted by habitat alteration, showed no significant trends in mean trophic level of fisheries catch over a 60-y period (13). In a study by Pauly et al (14) of aquatic ecosystems in Canada, freshwater fisheries did not show the declining trophic level in landings that were observed in marine fisheries on the west and east coast.…”