By Tyson Martin
Increasing demand for fish is resulting in smaller and fewer fish in the oceans. For island communities that rely almost entirely on fresh caught fish for their protein, this is very bad news. But little is known about whether their own subsistence fishing practices (fishing using traditional methods for immediate consumption) are harming the ecosystems they rely so heavily upon.
Lying in the middle of the North Pacific, the Marshall Islands provided an ideal opportunity to find out how subsistence fishing affects fish communities.
Most atolls are either commercially fished, or have small communities that still live pretty much as they did hundreds of years ago, relying on freshly caught fish from the ocean to feed their families. However, a few atolls have been uninhabited by people for the last 60-odd years following nuclear testing, giving us a near pristine baseline to compare fishing impacts against.
To examine the effects of subsistence fishing, we counted reef fish around three atolls each with different levels of fishing impacts; commercial (Majuro), subsistence (Ailuk); and near pristine (Rongelap).
We found that as expected, the commercially fished atoll (Majuro) had 70% fewer top predators (sharks etc.) than atolls that were either unfished or fished only for subsistence. Interestingly though, the commercially fished atoll also had the highest overall fish population by weight (biomass), presumably due to relaxed predation from the large fish and sharks removed by fisherman.
The fish communities around subsistence fished atolls were hardly different from the unfished or near pristine atoll.
Our new research suggests that just because a reef has high fish biomass, it may not necessarily be in great condition, and we also need to make sure that both predators and their prey are present in the correct proportions.
Additionally, we recommend that when faced with the opportunity to begin or increase the commercial capture and export of fish, island nations should remember that subsistence fishing by locals may not only provide food, but also keep reefs in an almost pristine condition. These reefs could then be used to generate other income through ventures such as ecotourism.
We suggest that in some cases where the human footprint is slight, coral reefs can have their fish, and we can eat them too.
This work appeared in ICES Journal of Marine Science