The Northwest Straits Initiative has known for years that lost and abandoned fishing gear damages habitat and kills marine species and tremendous amounts of old gear exist in Puget Sound.

But a new research study put some real numbers to that knowledge, finding that animals entangled in derelict fishing nets decompose in 10 days or less.

The study involved tagging and monitoring animals caught in four existing derelict fishing nets for one month. Divers monitored the nets at regular intervals, noting species, decomposition rate and tagging newly-entangled animals. The results showed some high kill rates, including just one of the nets monitored has killed more than 2,300 fish and 1,200 marine birds during the 15 years it was known to be derelict.

“During our normal removal operations, the number and type of entangled animals gives us a snapshot of the damage it has been doing,” Northwest Straits Commission director Ginny Broadhurst said. “Now we know that snapshot represents just about 10 days. The long-term impacts of this gear far exceeds what we’ve been able to record when we remove the gear.”

The number of fish, birds and invertebrates like crab was counted and calculated per day. No marine mammals were found in these four nets, although they have been found in other derelict nets in Puget Sound. The nets were removed at the end of the study.

“Finally, we have data demonstrating that derelict fishing gear is a major mortality factor and that removing it is a no-brainer,” said Joe Gaydos, Northwest Straits commissioner and a wildlife veterinarian with the SeaDoc Society.

The Northwest Straits Initiative has removed more than 870 derelict fishing nets (more than 200 acres) and estimates there are 4,000 more nets currently derelict in Puget Sound. In the removed nets were found more than 30,000 entangled animals, including 22 dead marine mammals, 378 dead birds, 1,022 live and dead fish, and 29,517 live and dead invertebrates.

More than 95 percent of the nets removed are estimated to have been derelict for more than five years. The Puget Sound Initiative has a goal of removing 90 percent of all derelict nets from Puget Sound by 2012.

The Northwest Straits Initiative is a citizen-driven, Congressionally-authorized program to restore and protect the valuable marine resources and habitats in northern Puget Sound and the Strait of Juan de Fuca. Marine Resources Committees in seven counties set local priorities, investigate conditions, sponsor restoration and outreach projects, and recommend science-based marine-policy to their respective local governments.

The full report on this study, “Rates of Marine Species Mortality Caused by Derelict Fishing Nets in Puget Sound, Washington,” is available here