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Bering Sea Baby Skates Indicate the Health of Alaska’s Marine Ecosystems


Skate egg cases provide protection against the elements as young skates develop.

 
A skate at Stage 5 of its life cycle.  


The complex life cycle of a skate.

Useful Links

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August 28, 2012

A healthy marine ecosystem is a productive marine ecosystem. Productive ecosystems translate to the potential to produce more fish and seafood for a growing global population as well as the potential to boost job growth.

That’s why one of NOAA Fisheries’ core missions is habitat conservation to support healthy and sustainable fisheries. In Alaska, NOAA’s managers and researchers collaborate with the North Pacific Fishery Management Council (Council) to identify productive marine habitats and make science-based recommendations for protecting this habitat. The Council serves as a sounding board for sharing information with the public and determining which protections, if any, should be put in place for these “habitat areas of particular concern,” also known as HAPCs.

Six Important Skate Nursery Areas Identified

NOAA scientists in Alaska have proposed six areas in the eastern Bering Sea as 'habitat areas of particular concern' for skates because they function as skate nurseries.

Skates are related to sharks and sting rays, and appear similar to rays. But skates do not give live birth like rays. Instead, skates produce large leathery eggs that provide protection to developing skates. These eggs are placed onto the sea floor in specific areas referred to as nurseries.

The Top of Undersea Canyons Are Ideal Nursery Areas

Nursery sites have been found on flat sandy areas at the tops of undersea canyons, such as the Pribilof Canyon in the eastern Bering Sea. These canyons may possess the best water conditions for development and successful hatching of skate embryos. Scientists estimate there are 16-19 such nurseries in the eastern Bering Sea for the eight most abundant skate species.

In the North Pacific, skates have been found to take more than three years to develop inside their egg case due to cold water temperatures. Because skates produce only a small number of offspring each year, they rely on high survival rates of juveniles to maintain healthy population levels. 

Skate Health Indicates Ecosystem Health

Scientists say the health of the skate population is a good indicator of overall health and productivity of Alaska’s marine ecosystem. Skates play a key role in the marine ecosystem as a food source for sperm whales, Pacific halibut, cod, Steller sea lions, and sharks.

Skates are also becoming a trendy food source for people. A small commercial fishery for skates developed in the Gulf of Alaska in 2003 and could expand to provide even more economic opportunities in the future. Maintaining a robust skate population is not only important to Alaska’s ecosystem, it may also provide economic growth.  

Avoid Nursery Areas to Safeguard Skates 

So what's the concern for skate nurseries? Skate experts say that during the lengthy development time that eggs and embryos are on the sea floor, they are highly susceptible to disturbance, damage, or destruction from fishing gear that contacts this same area. Fishing vessels generally try to avoid areas that are known to have high concentrations of skate eggs because egg cases get tangled in fishing gear. These egg cases are difficult to remove from trawl gear and add additional trip time, cost, and fishing effort.

It seems it would be in the best interest of both the skates and the fishing industry for vessels to avoid the skate nursery areas.

At its June 2012 meeting in Kodiak, Alaska, the Council announced that it will consider opportunities for finding out more about skate nurseries, including directing NOAA Fisheries to monitor the areas that were identified as ‘habitat areas of particular concern’ for changes in egg density and potential effects of fishing gear. They will need help from the fishing industry to identify areas of skate egg concentration and assistance in identifying research needs. The Council is also considering making research and monitoring of skate egg concentration a high research priority.

The Council plans to make a final decision on the ‘habitat areas of particular concern’ proposal at its meeting in Anchorage, Alaska in December 2012.