Examination of gear type efficacy, tagging methodology, and population structure for establishing a directed Enteroctopus dofleini fishery

Abstract

"In recent years, there has been a renewed interest in a directed fishery for North Pacific giant octopus, Enteroctopus dofleini. This species continues to be managed as a bycatch only species through the use of commisioner's permits primarily due to the lack of information on the basic ecology of E. dofleini and the logisitics of management. In the summer of 2007, we completed a survey in Kachemak Bay, Alaska, to determine the efficiency of different gear types for targeting E. dofleini, compared different methods of tagging individuals for movement and abundance estimates, and collected tissue samples for use in a genetic analysis of population structure. If a directed fishery develops in Alaska, our data suggest that unbaited lair pots may be the most effective means of capture while minimizing bycatch of other commercially important species. Most regions in Alaska lack sufficient data to estimate abundance and often estimates using catch-per unit of effort can be inaccurate. If mark-recapture methods are used to estimate abundance of octopus populations, then results from our tagging indicate that visible implant elastomer may be the most effective means of marking individuals. Genetic analysis of E. dofleini populations revealed an enigmatic pattern of population structure with two haplotype lineages. The large amount of sequence divergence at the COI locus may indicate the presence of a cryptic species within the E. dofleini complex. It appears that North Pacific giant octopus will continue to be managed as a bycatch-only species for the near-term future. It is essential that management agencies resolve both the phylogenetic and population structure, as well as confidently estimate abundances of the stocks identified before a directed fishery is opened"--Leaf iii