Farming-Up Coastal Fish Assemblages Through a Massive Aquaculture Escape Event
A Fish Article from All-Creatures.org

FROM

Humane Research Council (HRC)
May 2015

In other words, increasingly more fish farms are rearing predator species, and this process - also known as "farming up" - is marked by "the exploitation of wild fish stocks to feed high trophic level species." In addition, because fish farming doesn't take place in isolation - it is often carried out in large penned-in areas on coastal waters - there are further associated dangers. "Technical failures and sea storms provoke both recurrent-small or punctual-massive escapes across the coasts where open-net cage aquaculture is established," say the authors.

By Kilian Toledo-Guedes, Pablo Sanchez-Jerez, María E. Benjumea, Alberto Brito (BIOECOMAC, Universidad de La Laguna) 

Image by Flickr user Ivan.Walsh.com under Creative Commons License

Short Description:

Every year, millions of fish are "farmed" for human consumption. Fish farming carries with it a whole host of ethical problems, and is potentially dangerous environmentally. This study looks specifically at a "massive escape event" that occurred near the Canary Islands, and examines how fish farm escapes can hugely and irreversibly impact nearby marine areas. The research finds that, at the very least, risk assessment of fish farming needs to be clearer.

Abstract:

For animal advocates, there are obvious ethical implications with consuming fish, and these are amplified when the fish are farmed. The scale of the production of farmed fish, along with the issue of keeping wild animals in captivity, and the potential environmental impact are huge concerns. According to a study from the Canary Islands, fish farming (also called aquaculture), especially of high-trophic level fish, "is growing, especially in developed countries, as a result of a rising demand on these products and the highest profit obtained from carnivorous species." In other words, increasingly more fish farms are rearing predator species, and this process - also known as "farming up" - is marked by "the exploitation of wild fish stocks to feed high trophic level species." In addition, because fish farming doesn't take place in isolation - it is often carried out in large penned-in areas on coastal waters - there are further associated dangers. "Technical failures and sea storms provoke both recurrent-small or punctual-massive escapes across the coasts where open-net cage aquaculture is established," say the authors.

The subject of fish farm escapes has been researched previously, and many studies have pointed out a range of negative impacts that can be caused by the release of fish, such as genetic hybridisation, predation on native species, competition for trophic resources, and the introduction of parasites and diseases. In La Palma, an area close to the Canary Islands, there was a massive escape event that occurred between December 2009 and January 2010, due to huge waves generated from sea storms and the resulting stress on the aquaculture facilities. As a result, about 1.5 million fish, mostly sea bass, were released into the wild. This was the largest sea bass escape event worldwide. In this study, which examines the La Palma escape, the researchers "failed at detecting negative or positive correlations between number of escapees and abundance of other fish species" in the short term. However, they caution that other studies reveal such effects over a longer period of time: "other studies have revealed that the input of predators in a semi-closed systems can cause an alteration of trophic interactions and cascade effects." In this limited scale study, which took place just six months after the massive escape event, they found that "escapees were able to actively exploit available resources in natural habitats as the marine protected area (MPA)." So, even though the researchers were not able to ascertain the longer-term impacts, in this particular case, shorter-term effects were observed.

In their concluding remarks, the researchers note that further studies should take into account the "high mobility of escapees," and recognize that current remediation methods are not specific enough, so do not meaningfully resolve escapes. The study also states that, even if some management techniques were to be refined, this wouldn't help across all regions, because in some areas "wild counterparts cohabit with escapees" and "wild and escaped fish can only be differentiated after being caught." As aquaculture production is predicted to rise worldwide, the researchers note that scaling up current farming practices, and the types of species grown, "could lead to ethical and environmental issues," and recommend a better risk assessment and contingency plans. However, for animal advocates, the findings of this and other studies demonstrates the need to make further efforts towards ending the farming of fish, not simply mitigating its impact.

Original Abstract:

We investigated the changes on the mean trophic level of fish assemblages across different spatiotemporal scales, before and after a massive escape event occurred off La Palma (Canary Islands), which resulted in the release of 1.5 million fish (mostly Dicentrarchus labrax) into the wild. The presence of escaped fish altered significantly the mean trophic level of fish assemblages in shallow coastal waters. This alteration was exacerbated by the massive escape. A nearby marine protected area buffered the changes in mean trophic level but exhibited the same temporal patterns as highly fished areas. Moreover, escaped fish exploited natural resources according to their total length and possibly, time since escapement. New concerns arise as a “farming up” process is detected in shallow coastal fish assemblages where marine aquaculture is established.

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