A novel method for modeling age and length selectivity of sockeye salmon as applied to the Bristol Bay Port Moller test fishery

This paper presents a novel approach for assessing sources selectivity in test fisheries using the Port Moller test fishery (PMTF) as a case study. The PMTF intercepts sockeye salmon (Oncorhynchus nerka) migrating to Bristol Bay, Alaska to estimate run strength and timing. In 2011, the mesh size of gillnets used in the test fishery were decreased for half of the net panels to generate more accurate run estimates by correcting for greater selectivity of large 3-ocean fish relative to the smaller 2-ocean fish. Here we quantify two sources of age selectivity in the PMTF program, length selectivity parameterized by mean fish length (which should be corrected by the net mesh change) and length-independent selectivity, or residual program selectivity (which would not be impacted by the net change) both before and after the net change. Model parameters of selectivity show strong support that length selectivity was eliminated but residual program selectivity still exists after the reduction net mesh size. Our res...