Fish catches from Lake Tanganyika mainly reflect changes in fishery practices, not climate

Sarvala, Jouko; Langenberg, Victor; Salonen, Kalevi; Chitamwebwa, D.; Coulter, G. W.; Huttula, Timo; Kanyaru, R.; Kotilainen, Pekka; Makasa, S.; Mulimbwa, N’sibula; Mölsä, Hannu

doi:10.1080/03680770.2005.11902871

Cited by 31 publications

(56 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Purse seine fishery catch per unit effort in Lake Tanganyika has declined since 1962 and more steeply since 1985 (Sarvala et al 2006), certainly in part as the result of an increase in fishing effort by other fishing technologies, in particular the light-lift net fishery, which now dominates catches (Sarvala et al 2006). However, high fishing pressure alone may not be enough to explain the substantial decline in fish catch per unit effort at Lake Tanganyika, especially for short-lived zooplanktivorous Stolothrissa tanganyicae, which lives, on average, less than 1 yr and makes up the lion's share of the catch in Tanganyika.…”

Section: Discussionmentioning

confidence: 99%

The physics of the warming of Lake Tanganyika by climate change

Verburga

Hecky

2009

Limnology & Oceanography

124

View full text Add to dashboard Cite

Climate warming over the 20th century has increased the density stratification and stability of Lake Tanganyika, a deep rift valley lake. Here we examine the physical processes involved in and affected by the warming of the lake, and we discuss effects on lake productivity. The rate of net heat absorption by Lake Tanganyika has been 0.4 W m 22 since 1913, twice the rate in the global ocean, indicating stronger climate forcing in the East African region. Lakes warm through increased incoming long-wave radiation. While lakes in general will increase heat outputs in a warming climate, heat outputs will increase more slowly in deeper lakes than in shallower lakes. Temperatures have increased by 0.2uC at 1000 m in depth, in part because of reduced cool marginal inflows, while water surface temperatures have increased by about 1.3uC. This differential heating over depth has increased the density gradient through the water column, reducing the potential for vertical mixing and thereby limiting nutrient fluxes to the phototrophic zone. An increase in transparency, indicating a reduction in productivity as a result of the reduced vertical mixing, occurred both in Lake Tanganyika and in Lake Malawi, a similar deep tropical lake in which warming has also been documented.

show abstract

Section: Discussionmentioning

confidence: 99%

The physics of the warming of Lake Tanganyika by climate change

Verburga

Hecky

2009

Limnology & Oceanography

124

View full text Add to dashboard Cite

show abstract

“…However, this ecosystem has changed dramatically in recent decades; expanding deforestation (8), intensifying fishing efforts (9), rising water temperatures, and declining phytoplankton production (10)(11)(12) have all been concurrent with fishery declines. As a result, debate continues over the relative roles of fishing practices and climate change in Tanganyika's fishery declines (9)(10)(11).…”

mentioning

confidence: 99%

Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

Cohen

Gergurich

Kraemer

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

151

View full text Add to dashboard Cite

Warming climates are rapidly transforming lake ecosystems worldwide, but the breadth of changes in tropical lakes is poorly documented. Sustainable management of freshwater fisheries and biodiversity requires accounting for historical and ongoing stressors such as climate change and harvest intensity. This is problematic in tropical Africa, where records of ecosystem change are limited and local populations rely heavily on lakes for nutrition. Here, using a ∼1,500-y paleoecological record, we show that declines in fishery species and endemic molluscs began well before commercial fishing in Lake Tanganyika, Africa's deepest and oldest lake. Paleoclimate and instrumental records demonstrate sustained warming in this lake during the last ∼150 y, which affects biota by strengthening and shallowing stratification of the water column. Reductions in lake mixing have depressed algal production and shrunk the oxygenated benthic habitat by 38% in our study areas, yielding fish and mollusc declines. Late-20th century fish fossil abundances at two of three sites were lower than at any other time in the last millennium and fell in concert with reduced diatom abundance and warming water. A negative correlation between lake temperature and fish and mollusc fossils over the last ∼500 y indicates that climate warming and intensifying stratification have almost certainly reduced potential fishery production, helping to explain ongoing declines in fish catches. Long-term declines of both benthic and pelagic species underscore the urgency of strategic efforts to sustain Lake Tanganyika's extraordinary biodiversity and ecosystem services.climate change | Lake Tanganyika | freshwater biodiversity | fisheries | paleoecology

show abstract

“…Lakes can be extremely sensitive to short-and long-term changes in the weather and to the processes that take place in the catchment (Adrian et al, 2009;Carpenter et al, 2007;Pham et al, 2008). According to some other studies, the lake and its resources are seriously threatened by constantly increasing pressure from the human population residing around the lake and its watershed, and from unsustainable aquatic and terrestrial resource exploitation practices (Caljon, 1992;Cohen et al, 1993;Alin et al, 1999;Reynolds & Molsa, 2000;Sarvala et al, 2006;Jorgensen et al, 2006;Kamenya et al, 2008). Jorgensen et al (2006) has summarized the roles of over-exploitation of the biological resources (because of high fishing pressure and the use of destructive methods), siltation (due to erosion in the drainage area as a result of increased deforestation), untreated wastewater discharges, agricultural runoff, increased population, urbanization and industrialization and global climate change on the Lake.…”

Section: Discussionmentioning

confidence: 92%

“…Ogutu-Ohwayo et al (1997) have documented similar human impacts on the African Great Lakes. Sarvala et al (2006) reported that the purse seine fishery catch per unit effort in Lake Tanganyika has declined steeply since Phyto (lg C l -1 ) 15.0 --12.5…”

Section: Discussionmentioning

confidence: 98%

“…It should be noted that in recent decades the human population and settlements around the lake have expanded resulting in a local overexploitation of its resources, including the possible local depletion of fish stocks (Reynolds & Molsa, 2000;Sarvala et al, 2006;Jorgensen et al, 2006). This might also add to the fact that few fisheries statistics exist for Lake Tanganyika.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Possible effects of global climate change on the ecosystem of Lake Tanganyika

2011

View full text Add to dashboard Cite

Any change in the air temperature, wind speed, precipitation, and incoming solar radiation induced by increasing greenhouse gasses and climate change will directly influence lakes and other water bodies. The influence can cause changes in the physical (water temperature, stratification, transparency), chemical (nutrient loading, oxygen) and biological (structure and functioning of the ecosystem) components of the Lake. In this work an influence of the likely effects of the climate change on the above three components of Lake Tanganyika are studied by means of a simple ecological model. Simulations for the years 2002-2009 have been performed using the wind and solar radiation data from the National Centres for Environmental Protection (NCEP) reanalysis. Various possible climatic scenarios are studied by changing the surface layer depth, its temperature and the wind stress. Any change in any of the above physical forcing parameters modifies the timing and intensity of the dry season peaks of the biogeochemical parameters. It is seen that the gross production increases as temperature of the surface layer increases and its depth decreases. High temperature and low wind stress, reduces the biomass. The effects of a slight increase in lake water temperature on the Lake Tanganyika ecosystem might be mitigated by increased windiness, if the latter was sufficient to induce greater mixing.

show abstract

Fish catches from Lake Tanganyika mainly reflect changes in fishery practices, not climate

Cited by 31 publications

References 21 publications

The physics of the warming of Lake Tanganyika by climate change

The physics of the warming of Lake Tanganyika by climate change

Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems

Possible effects of global climate change on the ecosystem of Lake Tanganyika

Contact Info

Product

Resources

About