An overview on protection of corals and VMEs in fished and unfished areas
A number of international organizations including the UN General Assembly, Regional Fisheries Management Organizations, the Convention on Biological Diversity, etc. have identified deep-sea corals and their associated communities as vulnerable marine ecosystem components and recommended protections from anthropogenic activities. Within US waters protections have been increasing since about 2005. Most of the US management actions specific to addressing VME species have been to close areas of known or suspected coral to mobile bottom contact fishing gear. In Alaska about 20-30% of the eastern Bering Sea, Aleutian Islands and Gulf of Alaska is closed to mobile bottom contact fishing gear. However, many of these closures have focused on non-VME issues.
Beginning in 2012, the Alaska Fisheries Science Center undertook an effort to produce models of the distribution and abundance of deep-sea corals, sponges and pennatulaceans for the Gulf of Alaska, Aleutian Islands and eastern Bering Sea slope and outer shelf. The original models were based on bottom trawl survey data collected since 1990. In two cases, these models have been validated using an independent underwater stereo-camera survey. The results have shown that the distribution models are accurate for distribution (presence and absence) and less accurate for abundance.
Using the species distribution models, we evaluated the effect of historical fishing closures put in place to protect a variety of species including VME’s. Vessel monitoring system (VMS) data is also available for most commercial fishing vessels in Alaska and can be useful to examine patterns in occurrence of fishing tows In Alaska from 0 to ~43% of corals, sponges and pennatulaceans are protected from mobile bottom contact gear, depending on the ecosystem. The most extensive protections for corals and sponges are in the central and western Aleutian Islands where the majority of the high density areas are protected from bottom trawl gear.
Interestingly, during the underwater stereo-camera survey, densities of corals were found to be higher in the fished areas of the Aleutian Islands as opposed to the closed areas. The presence and density of deep-sea corals and sponges are linked to the presence of hard substrates. The proportion of transects with hard substrates in fished areas was higher than the proportion of transects with hard substrates in closed areas accounting for much of the difference. However, this result also highlights the fact that VMS data shows even within the fishery open areas in the Aleutian Islands, the majority of the seafloor is not actively fished.
In the eastern Bering Sea, we have looked extensively at the presence of evidence of fishing and potential impacts to benthic invertebrates. Overall, about 9% of individual sea whips were found to be damaged or dead (presumably due to both fishing and natural mortality). Evidence of fishing activity was present at 13% of transects in the region, but only ~3% of transects had evidence of both fishing and damaged taxa together. Other studies have found generally low levels of natural damage and mortality ~4-5% in deep-sea systems around the US. Research to reduce gear impacts has also been efficient at reducing damage to benthic organisms in the eastern Bering Sea. The overlap between commercial fishing activity and VMEs in the eastern Bering Sea appears to be extensive, but most VME supporting habitats are infrequently fished.
Monitoring of VME populations in protected and unprotected areas of Alaska has been limited to compiling a group of indicators including VME removals, fishing intensity, abundance trends from fishery surveys. A PICES working group has been actively examining potential indicators for VME’s in the wider North Pacific and will sponsor a topic session at the 2018 PICES Annual Meeting. Rudimentary population models are in development that will also assist in providing indicators of the status of VME organisms in a more quantitative framework and an example for corals in the Aleutian Islands will be briefly highlighted.