Steven A. Murawski

Integrated ecosystem assessments: developing the scientific basis for ecosystem-based management of the ocean.

Integrated ecosystem assessments challenge the broader scientific community to move beyond the important task of tallying insults to marine ecosystems to developing quantitative tools that can support the decisions national and regional resource managers must make.

Climate Change and Marine Fish Distributions: Forecasting from Historical Analogy

Abstract Analyses of 36 fish and squid species sampled in standardized bottom-trawl surveys of the northwest Atlantic Ocean (1967–present) revealed a continuum of distributional responses associated with seasonal and annual variations in water temperature. Mean and maximum latitude of occurrence of the species were regressed against average surface- and bottom-water temperatures and indices of relative abundance from spring and autumn trawl surveys. Significant (P ≤ 0.05) regression models were fitted for 17 of 36 species from spring and fall survey data. Variations in water temperature were significant in explaining changes in mean latitude of occurrence for 12 of 36 species in both seasons. Maximum latitude distribution responses to interannual differences in water temperatures occurred for pelagic species, including Atlantic mackerel Scomber scombrus and Atlantic herring Clupea harengus. Weighted mean catches of these species shifted poleward by 0.5–0.8 degree of latitude for each 1°C increase in avera...

Ten Commandments for Ecosystem-Based Fisheries Scientists

Abstract In an effort to accelerate the ongoing paradigm shift in fisheries science from the traditional single-species mindset toward more ecosystem-based approaches, we offer the following “commandments” as action items for bridging the gap between general principles and specifie methodologies. 1. Keep a perspective that is holistic, risk-averse, and adaptive. 2. Question key assumptions, no matter how basic. 3. Maintain old-growth age structure in fish populations. 4. Characterize and maintain the natural spatial structure of fish stocks. 5. Characterize and maintain viable fish habitats. 6. Characterize and maintain ecosystem resilience. 7. Identify and maintain critical food web connections. 8. Account for ecosystem change through time. 9. Account for evolutionary change caused by fishing. 10. Implement an approach that is integrated, interdisciplinary, and inclusive. Although the shift in worldview embodied in these commandments can occur immediately without additional funding, full implementation o...

Fisheries Bycatch: Implications for Management

Abstract A broad-based public consensus has emerged that bycatch should be minimized to levels approaching insignificance. This view, as reflected in U.S. and worldwide legislation and agreements, demonstrates the widely held belief that discarded portions of fishery catches (including economic resources, protected species, and unobserved mortalities of animals not caught) represent an unacceptable waste of natural resources. Bycatches in their various forms can have significant consequences for populations, food webs, and ecosystems. The economic effects of bycatches can influence not only the levels of yields to individual fisheries, but also may have major effects on allocations among competing fisheries. The lack of comprehensive monitoring programs in most areas to assess bycatches and integrate them into population and multispecies models seriously impedes a full understanding of bycatch consequences and the efficacy of measures for their amelioration. Nevertheless, where evidence for significant by...

Can We Manage Our Multispecies Fisheries

Abstract Fishery resources (fish, invertebrates, marine mammals, and reptiles) of the U.S. exclusive economic zone (EEZ, 3–200 nautical miles from the coast) are currently regulated under several pieces of key legislation enacted during the early 1970s. At that time fishery science was only beginning to appreciate the interactions among species and fisheries as being potential impediments to simultaneous realization of competitive management goals. Many of the important management problems currently faced in the EEZ are exacerbated by the incompatibility of regulations promulgated separately under these statutes, for what are ecologically- or technologically-related species. Reconciling the management of interacting species and fishermen will require an institutional framework for evaluating the multispecies/multifishery consequences of management decisions, and for articulating a clear set of compatible management goals for the various constituents. Traditional single-species biological reference points ...

Potential Economic Benefits from Efficient Harvest of New England Groundfish

Abstract Dissipation of economic benefits from commercial harvest of the multispecies groundfish resource in U.S. waters off New England was estimated from dynamic optimization of empirical bioeconomic models. Net economic value could be maximized by an estimated 70% reduction in fishing effort, resulting in a sevenfold increase in the size of the harvestable resource and a threefold increase in sustainable yield, Under these conditions, fishers, seafood industries, and consumers could benefit from an estimated US

Yield sustainability under constant-catch policy and stochastic recruitment

150 million increase in sustainable net economic value each year, including about

Population Dynamics of Anadromous Rainbow Smelt Osmerus mordax, in a Massachusetts River System

130 million in resource rent. Consumers in the region could profit further from the nutritional and health benefits of up to an additional 6 Ib of fresh fish per capita. Policies to achieve these benefits are highlighted. Augmenting state ownership of the resource with market transfers of individual effort or harvest quotas is preferred to open access, but common property or individual private property regimes are...

A Population Assessment of Butterfish, Peprilus triacanthus, in the Northwestern Atlantic Ocean

Abstract Current practices for computing maximum sustainable yield (MSY) from fisheries result in yields that are rarely maximized and never sustainable. We recast MSY determination as the maximization of constant catch, which is subject to the risk of stock depletion below levels necessary to generate the target constant catch. Monte Carlo yield models with stochastic recruitment functions were used to examine the effects of constant-catch policies on fishing mortality, catch, and stock size. Three additional output variables and their statistical properties were developed as indices of fishery variability and risk: delta catch, the change in catch between successive years; length of run, the number of successive years the target constant catch was attained; and the proportion of years in which the target constant catch was not taken. We constructed two stochastic yield models to account for different stock-recruitment relationships. The first used a statistical distribution of recruitment values in whic...

Definitions of overfishing from an ecosystem perspective

Abstract Population dynamics of anadromous rainbow smelt, Osmerus mordax (Mitchill), in the Parker River estuary, Massachusetts, were investigated during the spring spawning runs of 1974 and 1975, and the winter recreational fishery of 1974-1975. Growth (in length) was greatest in the first year of life, and nearly ceased by age V. Avon Bertalanffy growth function fitted to the data (l = total length, mm; t = years) is: lt = 256.29[1 - e-0.6393(t + 0.0018)]. The length (L, total length, mm)/weight (W, g) regression is: log10W = −6.0315 + 3.3592 log10L. Parker River fish were partially recruited to the spawning population at age I and were probably fully recruited at age II. Total mortality was lower for females than males. Total annual mortality of adults averaged 72%. Fifty percent selection to the angling fishery occurred at 166 mm. Modeled values of fishing mortality that result in greatest yield per recruit to both the present angling fishery and a simulated dipnet fishery on the spawning grounds woul...