Establishing the impacts of freshwater aquaculture in tropical Asia: the potential role of palaeolimnology

Abstract

Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisheries can, however, add severely to pressures on ecosystem functioning and services. In Southeast Asia, aquaculture in freshwater lakes contributes significantly to the economy and to reductions in poverty and nutritional insecurity. However, overstocking and excessive feeding of fish can lead to a degradation of affected water bodies, manifest as eutrophication, toxic algal blooms, losses of biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries. Projected increased warming and storminess associated with global climate change are likely to magnify existing problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is impossible to rectify in the short term using standard limnological approaches. This paper reviews the development of freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regulations and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring records, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands forming the Philippines.

Potential anthropogenic regime shifts in three freshwater lakes in Tropical East Asia

“…The cluster of lakes is designated a candidate key biodiversity area. Key biodiversity areas aim to ensure the in situ conservation of globally important biodiversity; areas that are suspected of supporting globally important biodiversity, but for which there are no conclusive supporting data, are designated candidate key biodiversity areas and are regarded as priorities for research in the Philippines (Legaspi et al., ).…”

An integrative approach to assess the impact of disturbance on native fish in lakes

“…To highlight the complex ways in which anthropogenic disturbance impacts fish communities and their subsequent response, we have selected three of the most widespread anthropogenic stressors, eutrophication, land use change and the introduction of non‐native fish. Readers are referred to the following for details on other disturbances on fish in lakes: climate change (Jeppesen et al ., 2010, 2012; Sharma et al ., 2011; Chu, Mandrak & Minns, 2005; Heino, Virkkala & Toivonen, 2009; Ficke, Myrick & Hansen, 2007; Hansen et al ., 2018), hydroelectric impoundments (Liermann et al ., 2012; Han et al ., 2008; Jellyman & Harding, 2012; Mattocks, Hall & Jordaan, 2017; Rytwinski et al ., 2017; Turgeon, Turpin & Gregory‐Eaves, 2019), pollutants (Lemly, 2002; Javed & Usmani, 2019; Johnson, 1968; Javed & Usmani, 2015), over‐exploitation (Allan et al ., 2005; Beeton, 2002; Ogutu‐Ohwayo, 1990; Smith, 1968) and fish aquaculture activities (Rennie et al ., 2019; Jia, Zhang & Liu, 2013; Legaspi et al ., 2015; Phillips, Beveridge & Ross, 1985). Freshwater fish life histories are complex with different life stages sometimes existing in different aquatic environments, e.g.…”

Changing water quality and thermocline depth along an aquaculture gradient in six tropical crater lakes

“…The scale of the human impact on tropical freshwater systems is substantial, often inhibiting their ability to provide the ecosystem services on which local populations depend (Legaspi et al, 2015;Briddon et al, 2020;de Leon et al, 2020;May et al, 2021). In the Philippines, as in many parts of Southeast Asia, the utilisation of freshwater lakes and their surrounding catchments for aquaculture, agriculture (e.g.…”