WASHINGTON (CN) – The National Marine Fisheries Service will create “consequence” closure areas to reduce the number of harbor porpoises incidentally caught by commercial gillnet fishing vessels.
The agency estimates that 866 harbor porpoises per year are killed as bycatch. The areas would be closed seasonally to any gillnet fishing if the annual bycatch target is exceeded for two consecutive seasons.
The Coastal Gulf of Maine Consequence Closure Area will be triggered if the average bycatch rates in the Mid-Coast, Stellwagen Bank, and Massachusetts Bay Management Areas, combined, exceed the target bycatch rate of 0.031 harbor porpoise takes per metric ton of fish after two consecutive management seasons.
The Cape Cod South Expansion and East of Cape Cod Consequence Closure Areas, will be triggered if the average bycatch rate in the Southern New England Management Area exceeds the target bycatch rate of 0.023 harbor porpoise takes per metric ton of fish in two consecutive management seasons.
If triggered, these areas will be closed annually to gillnet fishing from February through April.
If all three closure areas were triggered, the agency estimates that approximately 30 percent of the gillnet fleet could be affected, resulting in a decrease in annual landings of 4 percent with an approximately $2 million decrease in revenues per year and a reduction in harbor porpoise mortality by about 671 porpoises.
Under the Marine Mammal Protect Act, the agency created the Harbor Porpoise Take Reduction Plan with the goal of decreasing harbor porpoise deaths resulting from their getting stuck in gillnets to approximately 60 animals, or about 10 percent of the species potential biological removal level, or the number of animals which can be lost per year before the reproductive potential of the populations falls below sustainability.
The agency believes that the Gulf of Maine/Bay of Fundy stock of harbor porpoises, whose range stretches from Maine to North Carolina, can lose about 610 animals per year before the sustainability of the stock is threatened.
Another way the agency hopes to reduce porpoise deaths is through the use of so called “pingers” which are devices that attach to the gill nets and emit a sonic burst that warns porpoises away from the nets. Pingers must be placed every 300 feet on gillnets that exceed 300 feet.
The agency is expanding the use of pingers — which vessel owners buy and maintain at their own expense — to incorporate almost the entire range of the harbor porpoise. As their name implies, harbor porpoises live in coastal areas and river estuaries, and sometimes venture hundreds of miles inland by river and canal. The mammals can reach 167 pounds and six feet in length and are the smallest species of porpoise.