Matanuska-Susitna Borough

Salmon Research: Fishing Depths of ESSN Setnets

Scope

Kintama will prepare an analysis that will determine the actual fishing depth of shallow (29 mesh), mid-depth (36 mesh) and conventional deep (45 mesh) gill nets fished in the East-Side Set Net (ESSN) fishing zone of Cook Inlet and establish the level of variability in maximum achieved net depth between fishing sites and in nets with different gear construction.    They will analyze collected data and establish how net depth varies by net type, in different parts of the tidal cycle and in different geographic regions of the setnet zone. This data can then be used to engage the fishing industry, ADF&G, Board of Fisheries and others to modify harvest allocations.

Timeline: November 2015-June 2016

Project Benefits

Project Status

Kintama developed a cooperative agreement with four commercial fishermen participating in the ESSN fishery in 2015 to directly measure the bottom depth of their nets using time-depth recorders.  These data allowed a calculation of the average effective depth of various net types (29, 36, and 45 mesh deep constructions) over different parts of the tidal cycle.  The study indicated that actual bottom depths achieved by setnets in Cook Inlet are strongly affected by tidal currents demonstrating that, except for very brief periods around the times of slack water, all currently used setnet constructions fish far shallower than originally thought.  Therefore, reductions in Chinook harvest by the ESSN can be achieved in one of two principle ways: a) by restricting fishing to avoid periods of slack water when deep nets hang down to their full depth, or b) by restricting the number of meshes used in setnets to reduce the maximum depth nets reach during periods of slack water.