Wild capture fisheries produce 90 million tonnes of food each year and have the potential to provide sustainable livelihoods for nearly 40 million people around the world (http://www.fao.org/3/a-i5555e.pdf). After decades of overfishing since industrialization, many global fish stocks have recovered, a change brought about through effective management. We provide a synthetic overview of three approaches that managers use to sustain stocks: regulating catch and fishing mortality, regulating effort and regulating spatial access. Within each of these approaches, we describe common restrictions, how they alter incentives to change fishing behaviour, and the resultant ecological, economic and community‐level outcomes. For each approach, we present prominent case‐studies that illustrate behaviour and the corresponding performance. These case‐studies show that sustaining target stocks requires a hard limit on fishing mortality under most conditions, but that additional measures are required to generate economic benefits. Different systems for allocation allow stakeholder communities to strike a locally acceptable balance between profitability and employment.

Association with physical structure or conspecifics can impact individual growth and survival. The necessity and strength of these associations changes with environmental conditions and ontogeny, acting in concert or opposition to influence an individual's behavior and ultimate success. We conducted a field experiment on the San Joaquin River, California, with juvenile Chinook salmon (Oncorhynchus tshawytscha) to test hypotheses related to the impacts of physical structure proximity and environmental and ontogenetic change on aggregating behavior of a migratory fish. We created orthogonal combinations of structural cover, turbidity, and juvenile Chinook salmon size and density by manipulating the location of artificial structure within net pens at three sites along the lower river and recorded observations of juvenile salmon swimming in aggregations with underwater video cameras. We selected the most parsimonious generalized linear mixed effects model via Akaike Information Criteria to analyze the effects of structure proximity, turbidity, and salmon size and density on aggregating behavior. The proportion of our observations composed of fish in aggregation increased significantly when fish were >3.5 m from structure; the strength of this effect declined significantly as turbidity, fish length, or fish density increased. We observed a significant decline in aggregation behavior when turbidity increased from 0.5 to 8.5 NTU and fish were more than 3.5 m from physical structure. Turbidity had minimal impact on behavior of fish within 1 m of structure. The proportion of our observations composed of fish in aggregation increased significantly when mean fish fork length increased from 45 mm to 80 mm, or fish density increased from ~0.2 n/m2 to 3.5 n/m2. Collectively, these results highlight how changes in the physical environment (i.e., structure and turbidity) and ontogeny interactively affect the frequency at which juvenile salmon swim in aggregation.

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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 was decreased for half of the net panels to generate more accurate run estimates by correcting for greater selectivity of larger 3-ocean fish (fish that have spent 3 years in the ocean) relative to smaller 2-ocean fish (fish that have spent 2 years in the ocean). 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, which we refer to as residual program selectivity (which would not be impacted by the net mesh change), both before and after the net change. Model parameters of selectivity show strong support length selectivity was eliminated, but residual program selectivity still existed after the reduction in net mesh size. Our results demonstrate the necessity of considering both vulnerability and accessibility to fishing gear when assessing selectivity in test fisheries.

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