The Haunted Fjord: Patterns and Implications of Ghost Nets in Puget Sound and the Northwest Straits

Derelict fishing gear--lost or abandoned commercial and recreational fishing nets, lines, pots, and traps that sit or float underwater--can remain in the marine environment for years. Unseen and largely unquantified, this marine debris can trap and kill a variety of target and non-target marine organisms.  Since 2002, a project removing derelict gillnets from Puget Sound and the Northwest Straits has documented the capture and mortality of many marine taxa.  Of the more than 3800 derelict fishing nets, the vast majority (n=3675) are gillnets, while the remainder are purse seines, trawl nets, and aquaculture nets.  Of the gillnets recovered, most were from the San Juan Islands and in northern Puget Sound and from high relief rocky and boulder habitats.  Most were relatively small in size (≤ 1,000 m² in area), still in relatively good condition, and stretched open to some extent (i.e., maximum suspension > 0 m), which enhances their ghost fishing potential.  Specimens collected during gear recovery are tallied and identified to the lowest possible taxon as nets are pulled onboard or in the lab using external characteristics or osteological characters.  Of the 93,000 organisms recovered, approximately 89,700 were marine invertebrates, 2400 were marine fishes, 800 were marine birds, and 50 were marine mammals; 43% of invertebrate, 80% of fish, and 100% of birds and mammals were recovered dead.  We have documented mortality in fully 70% of recovered gillnets, and we have identified at least 140 species of marine invertebrates, 41 species of marine fishes, 17 species of marine birds and 4 species of marine mammals during derelict gear recovery, some of which are species of commercial or conservation concern.  Mortality patterns documented during derelict gear recovery provide information on the breadth of taxa impacted; however, the numbers of animals observed during gear recovery are endpoint snapshots of the damage caused over derelict lifetime of the gear--the proverbial tip of the iceberg.  Advances in side-scan sonar technology are improving ongoing surveys to locate remaining derelict gear throughout Puget Sound and the Northwest Straits, and efforts are underway to simulate derelict net catch rates over time and model turnover rates due to decomposition and scavenging to better estimate mortality of marine taxa and impacts due to derelict fishing gear.  These efforts will help prioritize removal of remaining derelict gear as well as put this mortality source in context for local and regional species of economic and conservation concern.