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The Biology and Assessment of Rockfishes in Puget Sound
 
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The Biology and Assessment of Rockfishes in Puget Sound

Category: Fish/Shellfish Research and Management - Fish/Shellfish Research

Date Published: September 2009

Number of Pages: 208

Publication Number: FPT 09-04

Author(s): Wayne A. Palsson, Tien-Shui Tsou, Greg G. Bargmann, Raymond M. Buckley, Jim E. West, Mary Lou Mills, Yuk Wing Cheng, and Robert E. Pacunski

EXECUTIVE SUMMARY:

This technical review supports and is a source document for the Puget Sound Rockfish Conservation Plan. It summarizes the current knowledge of rockfish biology in Puget Sound (life history, habitat usage, and ecosystem linkages), provides an overview of the exploitation history of rockfishes, and examines their current stock status. The review also includes a series of recommendations to improve the understanding and management of rockfishes in Puget Sound. Puget Sound includes all the inland marine waters of Washington including the U.S. portions of the Straits of Juan de Fuca and Georgia, the San Juan Islands, Puget Sound proper, and Hood Canal.

Rockfishes are bottomfishes managed under the auspices of the Puget Sound Groundfish Management Plan and are co-managed with the Treaty Tribes of Washington. The present management plan by the Washington Department of Fish and Wildlife implements a precautionary policy for groundfish management. However, previous management efforts have ranged from targeting recreational and commercial fisheries on rockfish to passive management. As rockfish stocks declined during the past three decades, the Department has progressively restricted the harvest opportunities for rockfish by eliminating targeted commercial fisheries, reducing recreational bag limits, and discouraging or eliminating recreational fisheries targeting rockfish in Puget Sound.

Rockfishes in Puget Sound are a diverse group that form mixed species assemblages and require speciesspecific habitats at different life-stages. Rockfish have evolved to complex life strategies adapted for long survival, slow growth, late age-at-maturity, low natural mortality rates, and high habitat fidelity. Reproduction follows a pattern of irregular successful recruitment events. Population structure is highly dependent upon the evolutionary and ecological patterns of each species. Copper, quillback, and brown rockfishes living south of Port Townsend form a unique population separate from northern waters. Rockfishes feed on a wide variety of prey, including plankton, crustaceans, and fishes. Rockfishes are prey for a variety of predators including lingcod and other marine fishes, marine mammals, and marine birds. Rockfishes are very susceptible to barotrauma or being captured and brought to the surface from depth.

The complex oceanography and benthic topography of Puget Sound influences rockfish distributions and population characteristics at all life-stages. Most adult rockfish are associated with high-relief, rocky habitats, but larval and juvenile stages of some rockfishes make use of open water and nearshore habitats as they grow. Nearshore vegetated habitats are particularly important for common species of rockfish and serve as nursery areas for juveniles and later provide connecting pathways for movement to adult habitats. A system of marine reserves in Puget Sound provides rockfishes with protection from harvest and provides a baseline for ecological and natural demographic information for stock assessment and conservation.

Rockfish have been harvested by Native Americans and commercial and recreational fishers in Puget Sound. Rockfish harvests prior to 1970 were small relative to those between the mid-1970s through the mid-1990s when both recreational and commercial fishing effort increased. In 1974, a federal court decision reallocated salmon harvest on an equitable basis between tribal and non-tribal harvesters. Bottomfish and their fisheries were popularized for their sport, value, and healthful benefits, and previous non-tribal effort shifted to fishing for bottomfish. Since 1995, tribal fishers can harvest up to 50% of the rockfish quota. However, tribal harvests have accounted for an average 1% the total rockfish harvest since 1991. Regulations enacted during the past decade to conserve rockfishes reduced recent harvests by 90%.

The present status of rockfishes in Puget Sound was characterized using fishery landings trends, surveys, and species composition trends to evaluate rockfish stocks’ vulnerability to extinction. These evaluations rely upon fishery-dependent and independent information to detect changes over time. Conventional agestructure population models or biomass dynamic models were not applied due the lack of long-term catch data and associated biological information. The American Fisheries Society’s Criteria for Marine Fish Stocks were modified as a robust approach to establish stock status. These criteria are based upon life history parameters relating to population productivity and compare the magnitude of stock trends over ecologically appropriate time scales. Four status categories were based upon the magnitudes of trends and included Healthy, Precautionary, Vulnerable, and Depleted. Most rockfish species were in Precautionary condition, however, copper rockfish were Vulnerable in South Sound and quillback rockfishes were Vulnerable and Depleted in North and South Sound, respectively. Based upon stock assessments in adjacent coastal waters, yelloweye and canary rockfish were in Depleted status in North and South Sound. The relatively deepwater greenstriped rockfish, redstripe rockfish, and shortspine thornyheads were in healthy condition as were stocks of Puget Sound rockfish in South Sound.

The health of rockfish stocks in Puget Sound is impacted by factors that remove excessive numbers of individuals, chronically alter or degrade their habitats and block life history pathways, or affect other species that increase predation, disease, or competition. Many stressors potentially limit the productivity of rockfish stocks in Puget Sound and include fishery removals, age truncation, habitat disruption, derelict gear, hypoxia, predation, and fishery removals of larger and older individuals. These stressors may have even greater impacts when stocks are at low levels causing, higher mortality rates that can drive stocks to dangerously low levels. Among the potential stressors, fishery removals, derelict gear, hypoxia, and food web interactions are the highest relative risks to rockfish in Puget Sound. Chemical contamination is a moderate risk manifested by undetermined reproductive dysfunction associated with exposure to endocrine disrupting compounds, loading of larvae with persistent organics via maternal transfer, exposure of pelagic larvae to toxics via contaminated prey, and exposure of long-lived adults to toxics like polychlorinated biphenyl compounds that accumulate over the life of the fish. These are most likely to impact rockfish living in urban areas but may be more widespread in the food web.

Based upon this review of information and the condition of rockfish stocks in Puget Sound, a series of recommendations were developed to improve the conservation and management of rockfishes in Puget Sound. Principal recommendations are to improve our knowledge of rockfish in the ecosystem and their habitat requirements; better indentify, quantify, and control stressors on rockfish stocks; improve the management of rockfishes by evaluating the effectiveness of marine reserves, minimizing bycatch and accounting for all catch; and improve stock assessment by conducting comprehensive and frequent surveys, estimating life history parameters such as maturity, growth and mortality; better defining stocks and populations through genetic analysis; and developing quantitative models to reconstruct and analyze the abundance and demographic population structure.