Conserving Tropical Fish Diversity, by Emma Hultin

Freshwater fish, despite occupying only 0.3% of Earth’s available water, comprise about 25% of all vertebrates with over 15,000 extant species (IUCN 2015); however, this incredible diversity is not fully explored and frequently goes unappreciated as most conservation funding and attention often goes to fish of commercial value. There is also a great deal still unknown about the impacts of human development on non-game fish assemblages. This becomes a more pressing issue as the human population continues to expand and alter the landscape. One particular region of concern is the tropics. Globally, tropical freshwater fish have the highest functional diversity but are also highly vulnerable to anthropogenic changes. Tropical fish are understudied and by not documenting and conserving them we are missing a crucial element of freshwater fish diversity (Anderson & Maldonado-Ocampo, 2010).  Unfortunately, many of the countries in which these ecosystems exist do not have the resources to fund extensive fishery studies, a tragedy that could lead to the loss of vast amounts of diversity before it has even been discovered. There is an urgent need to increase efforts to research and conserve the diversity of tropical fishes. It is important that we understand not only the species that occupy an ecosystem but also the interactions within these diverse assemblages. For example, complex interactions may mean that a common species is key to the survival of a rare one and without that understanding any restoration effort for that rare species may be unsuccessful if the common species is not also protected (Frimpong, 2018).

Research on tropical freshwater fish should emphasize the importance of smaller streams. Small streams account for the most stream miles within a watershed and cumulatively provide more aquatic habitat than larger rivers (NAACC, 2019). They are also the site of leaf litter input, woody debris accumulation, and harbor invertebrate populations that feed fish. Currently, there is a gap in understanding the nuanced interactions between fish in these small streams. The impacts of losing the current assemblages are unknown, and measures of diversity are not comprehensive enough to develop management plans without consideration of habitat specific relationships of the assemblages (Assis de Carvalho & Tejerina-Garro, 2015). 

The Amazon rainforest is fed by a rich network of creeks, streams and rivers. Informal road construction is now endangering this critical ecosystem.  Photo by Rickey Rodgers, Reuters

Currently there are efforts being made by South American nations to conserve their fish populations. Andean fishes are among the most understudied vertebrates in the world. Nearly 40% of Andean fish are endemic and research shows they are highly vulnerable to climate change and human activity (Leal, et al., 2018). Other studies in the Amazon basin have examined the impact of agriculture and land disturbance on Amazonian stream fish and found that management of whole basins is needed to protect aquatic species (Castello, et al., 2013).

There are many potential options for the measurement and conservation of diversity. For example, work done in Japan demonstrated the use of priority mapping for protecting habitat of threatened fish (Onikura, Nakajima, Inui, & Kaneto, 2016). The aforementioned Amazon study suggested conservationists should connect land management with instream habitat conditions (Castello, et al., 2013). Terrestrial protected areas have also proven effective for conserving fish diversity in Lake Tanganyika which could translate into a useful strategy to protect other impaired aquatic ecosystems (Britton, et al., 2017). While the implementation of these programs and studies is a good sign for the future of freshwater fish conservation, there is still a need to increase efforts to study and conserve the diversity of tropical freshwater fish.

References

Anderson, E. P., & Maldonado-Ocampo, J. A. (2010). A regional perspective on the diversity and conservation of tropical Andean fishes. Conservation Biology, 25(1).

Assis de Carvalho, R., & Tejerina-Garro, F. L. (2015). Relationships between taxonomis and functional components of diversity: implications for conservation of tropical freshwater fishes. Freshwater Biology, 60(9).

Britton, A. W., Day, J. J., Doble, C. J., Ngatunga, B. P., Murrell, D. J., Kemp, K. M., & Carbone, C. (2017). Terrestrial-focused protected areas are effective for conservation of freshwater fish diversity in Lake Tanganyika. Biological Conservation, 212.

Castello, L., McGrath, D. G., Hess, L. L., Coe, M. T., Lefebvre, P. A., Petry, P., . . . Arantes, C. C. (2013). The vulnerability of Amazon freshwater ecosystems. Conservation Letters, 6(4), 217-229.

Frimpong, E. A. (2018). A case for conserving common fishes. PLOS Biology , 16(2).

IUCN. (2015). Freshwater fish diversity . Retrieved from IUCN Freshwater Fish Specialist Group: http://www.iucnffsg.org/freshwater-fishes/freshwater-fish-diversity/

Leal, C. G., Barlow, J., Gardner, T. A., Hughes, R. M., Leitao, R. P., Mac Nally, R., . . . Dary, E. (2018). Is environmental legislation conserving tropical stream faunas? A large scale assessment of local, riparian, and catchment-scale influences on Amazonian fish. Journal of Applied Ecology, 55(3), 1312-1326.

NAACC. (2019). North Atlantic Aquatic Connectivity Collaborative. Retrieved from Importance of Small Streams: http://streamcontinuity.org/naacc/ecological-concerns/importance-small-streams

Onikura, N., Nakajima, J., Inui, R., & Kaneto, J. (2016, July). Priority maps for protecting the habitats of threatened freshwater fishes in urban areas: a case study of five rivers in the Fukuoka Plan, northern Kyushu Island, Japan. Ichthyological Research, 63(3), 347-355.