Offshore Fisheries Research Articles

A Bioeconomic Analysis of the Northern Baltic Salmon Fishery: Coexistence versus Exclusion of Competing Sequential Fisheries

We develop a bioeconomic model of the northern Balticsalmon fishery that takes into account thesimultaneous harvest of wild and reared salmon. Weassess the optimal harvest allocation between thecommercial offshore, inshore, and estuary fisheries,and the recreational river fishery that sequentiallyharvest the salmon stock. We restrict the solution tospawning stocks sufficient to preserve the wildsalmon. Empirical results suggest closure of theoffshore and inshore fisheries. Optimal managementenhances the wild stock, and results in substantialeconomic gains to the fishery. Current fisheryregulation improves the performance of the fisheryover open access, but fails to utilize the fullproductive potential of the resource.

Empirical Analysis of Offshore Fishery Resource Management Measures in Kyoto Prefecture: Case of the Danish Seine Fishing

Empirical Analysis of Offshore Fishery Resource Management Measures in Kyoto Prefecture: Case of the Danish Seine Fishing

A Biomass Index for Northern Shrimp (Pandalus borealis) in Davis Strait Based on Multiplicative Modelling of Commercial Catch-per-unit-effor Data (1976-97)

Four biomass indices for the northern shrimp (Pandalus borealis) stock in Davis Strait, derived from commercial catch-per-unit-effort (CPUE) data, were analysed by multiple regression to construct a single time series with the ultimate goal of tracking trends in stock biomass during the period 1976 to 1997. Indices from the offshore fisheries have been used previously in stock assessments while an index derived from logbook data for small inshore vessels operating around Disko Island has not been presented previously. The analysis used multiplicative models and linked catch rate to vessel fishing power, temporal and spatial availability and overall annual biomass density. In two of the indices, the temporal (MONTH) and spatial (AREA) effects were modelled as interaction terms. Other second order effects were treated as random error. The AREA*MONTH interaction term corresponds to an annual migration or behavioural pattern. The procedure corrects for increases in technological efficiency over the 22-year period due to fleet renewal but changes in the efficiency of individual vessels were not accounted for. The four indices were combined, weighted by the area of the total fishing grounds each index represented. The combined index was indicative of the biomass density for shrimp greater than about 17 mm in carapace length. During the 1976–88 period, the index was higher than from 1989 onwards. The combined index showed agreement with research survey biomass estimates but the contrast in the data was low during the period of comparison (1988–97). The combined CPUE index was applied to the total catches to derive estimates of total standardized effort. This effort index increased substantially in the late-1980s.

FISHERIES IN A SEA OF CHANGE: ECOLOGY AND OCEANOGRAPHY OF NEW ENGLAND'S FISHING GROUNDS

This paper serves to set the stage for the conference on the history, status, and future of New England's offshore fisheries. From a global perspective, it provides a brief overview of the geological, physical, and biological processes and features that make New England one of the world's most productive temperate shelf regions, exceeding the primary and secondary production of other renowned temperate fishing grounds. Bathymetry, climate, and tides create a complex mixing regime that enhances nutrient cycling and primary productivity especially over Georges Bank and northeast Gulf of Maine. The glacially influenced coast and seabed create a unique benthic habitat along the US east coast that is a nursery to lobsters and cod, two of the regions most valuable fisheries. Considering the diversity of its habitats, however, New England's marine fauna are rather impoverished due to extinctions related to polar cooling, glaciation, and the absence of suitable refuge habitat to the south. Today's faunal distributions are attributed to recovered ranges pushed south during the glaciation and reinvasions from Europe. The steep north-south thermal gradient along the coast makes it a faunal transition zone. Over the past four centuries, man has contributed to dramatic shifts in the composition of New England's marine biotic communities through harvesting and species introductions. Growing human pressure and the dynamic nature of the productivity of New England waters raise increasing concern over the sustainability of its fisheries.

FEDERAL REGULATION OF NEW ENGLAND FISHERIES: A DIFFERENT POINT OF VIEW

Management of New England's offshore fisheries began in 1950, following ratification of the International Commission for the Northwest Atlantic Fisheries treaty. Due to both limited authority and management protocols, sustainable fisheries were not achieved. Frustrated with severe overfishing, both the United States and Canada opted to declare 200-mile fishery zones effective in 1977. Unfortunately, US jurisdiction within 200 miles failed to prevent overfishing. Previously blamed on foreign vessels, the near demise of offshore stocks in recent years was caused by the domestic fleet. New England's groundfish stocks thus reached their lowest levels since statistics were first maintained. The history of management efforts and the factors that led to today's crisis are examined. If New England's fishing industry is to once again become a viable and vibrant enterprise, new and creative management concepts must be considered.

THE HISTORY, STATUS, AND FUTURE OF THE NEW ENGLAND OFFSHORE FISHERY: INTRODUCTION TO THE PROCEEDINGS

Any regular reader of a New England daily newspaper is aware that all is not well in our offshore waters. Commercial harvests of fish have been dropping and many fish populations are in trouble globally, even in our own Northwest Atlantic region. In 1995, the National Marine Fisheries Service surveyed 201 species groups of US fish and judged over 60% to be either fully or over utilized. By 1998, the National Academy of Sciences estimated that 80% of commercially harvested fish species were fully or over utilized. Declines in fish stocks and subsequent fishing restrictions have translated into huge decreases in income and employment opportunities, both in New England and adjacent Canada. One report indicates closures to fishing on Georges Bank in the early 1990s cost 14,000 jobs in New England while Grand Banks closures caused 30,000 to become unemployed in Newfoundland. Most recently, in southern New England, a still mysterious die-off of lobster in Long Island Sound has thrown what was once a fairly stable segment of the industry into complete turmoil. Contrary to the general consensus on declines in numbers of commercial fish and in the number of people employed in the industry, there is considerable debate about the cause of the problem. How much is simply due to overfishing and how much to misguided regulation, pollution, or other factors is hotly debated. The History, Status, and Future of the New England Offshore Fishery Conference, held at Connecticut College in April 1999, was the second such gathering sponsored by the Goodwin-Niering Center for Conservation Biology and Environmental Studies. Like its predecessor, which dealt with the topic of New England forests (proceedings in Northeastern Naturalist 5(2), 1998), this two-day meeting was designed to examine a fairly specific subject from as many different points of view as possible. Our goal was to produce an insightful overview of current scientific, regulatory, economic, sociological, and conservation perspectives on the New England offshore fishery. We began planning this event shortly after the reauthorization of the Magnuson-Stevens Act, which governs federal management of fisheries outside of coastal state waters. In the spirit of Connecticut College’s mission to foster the liberal arts, we held our ban-

CLOSING THOUGHTS: A GLIMPSE AT THE NEW ENGLAND OFFSHORE FISHERY IN 2061

The range of perspectives on New England offshore fishery contained in preceding articles, reflecting wide breadth of views expressed by speakers at Conference on History, Status, and Future of New England Offshore Fishery held at Connecticut College on April 16 17, 1999, is truly impressive. The written contributions parallel oral presentations, allowing reader to note marked degree of respect between two essentially distinct communities, fishers on one hand and governmental manager-scientists on other. Given nature of their respective livelihoods, these two communities often find themselves at odds with one another. A careful reading of foregoing papers leaves us with an appreciation of how much hard-earned information has been acquired over years about our coastal and offshore marine environment, about various fish populations that reside therein, and about multi-faceted fishing industry that harvests these resources. We are also left with a sense of how intrinsically complex these natural and economic systems are, and, as a consequence of their complexity, how far we have yet to go before learning enough to effectively manage these systems. Beneath respect alluded to previously, a degree of ambivalence can perhaps be detected in some of presentations by fishing industry about many of conclusions put forth by scientists, modelers, and statisticians. One whose roots are firmly in academic community is left with somewhat hollow feeling that he or she may, to some degree, be witnessing time-honored tactic of blaming messenger. We as a society will only at our peril avoid recognition of inevitable consequences of ever-increasing demand in face of limited supply. A dozen years from now, on occasion of 100th Anniversary of Connecticut College, if it hosts another conference on New England offshore fishery, will papers report that plight of this fishery was much improved in intervening decade? Will some government bureaucracy, some association of fishing industry, some community of scientists, or a combination thereof have managed to cut Gordian knot comprised of inter-twining strands of the facts of economic life and the truths of a complex ecosystem? One need not introduce implications of potential climate change, nor be a pessimist by nature, to hesitate in answering in unequivocal affirmative.

Interpreting the collapse of the northern cod stock from survey and catch data

Sequential population analysis reconstructions of the northern cod (Gadus morhus) stock using survey and catch data formed the basis for the scientific advice for substantial reductions in catch quotas in the late 1980s. However, the model failed to provide acceptable reconstructions of the population in subsequent stock assessments when data for the 1990s were added. The model assumes constant age-independent instantaneous rate of natural mortality, accurate catch reporting, and a constant linear relationship between the survey index at age and the population size at age. It seems likely that one or more of these assumptions failed to hold around the time of the collapse. Diagnostic studies were carried out to determine the magnitude of the departure from the assumptions required to allow the model to fit the data. Information related to changes in natural mortality, fishing activity, and survey catchability is reviewed to evaluate the plausibility of departures from model assumptions of the magnitude estimated. It is concluded that unreported deaths caused by the offshore fishery may be most plausible as the main contributing factor to lack of model fit but that factors such as increased natural mortality, and possibly changes in survey catchability, also played a role.

Closing Thoughts: A Glimpse at the New England Offshore Fishery in 2061

Closing Thoughts: A Glimpse at the New England Offshore Fishery in 2061

Scientific and Cleanup Response to the Idoho-Qit Oil Spill, Nigeria

On 12 January, 1998, a 24 inch pipeline from the IDOHO platform to the Mobil Qua Iboe terminal ruptured. This resulted in the release of approximately 40 000 bbl of Qua Iboe light crude oil into the marine environment. In response to the spill, cleanup and containment equipment were immediately deployed. Dispersant application played an important role in the cleanup response because the bulk of the oil remained offshore and was transported westward by prevailing currents, thus providing an extended opportunity for treatment at sea. As a result of dispersant application, natural dispersal and evaporation, over 90% of the oil was dispersed and evaporated offshore. Heavy shoreline oiling was limited and localized, with oiling of sensitive estuarine mangrove habitats limited to a few locations. Remnants of the spill that tracked 5–10 km offshore from the spill source were observed at Lagos harbor, about 900 km west of the spill site. Most of the exposed sand beaches in the spill zone self-cleaned within 2–3 weeks and cleanup of the limited number of heavily impacted shoreline areas recovered approximately 1000 bbl of oily waste. A national and international team of scientists was convened within 24 hours and initiated scientific studies to measure the short-term impact of the spill on environmental resources important to local human activities. Elements of the short-term scientific program were (1) an offshore component, including fisheries, benthos, chemistry, microbiology; (2) a riverine/estuary component, including extensive water analyses to detect any spill input to waters used by local settlements and chemical analysis of local fish market samples. The results of the short-term scientific study indicated that any initial environmental effects were limited and localized. Based on the initial scientific program, a larger follow-up scientific program was initiated on September 15, 1998. This involved a multi-disciplinary program with the following components: offshore fisheries and benthic studies; a shoreline fate and effects program; a study of impacts to estuarine mangrove habitats; and a study of any socioeconomic and human health effects. The study plan was based on comparisons of data from spill zone and non-spill zone locations. The key elements of the study design of this comprehensive longer term study are described.

Effects of stock-specific and environmental factors on the feeding migration of Atlantic salmon (Salmo salar) in the Baltic Sea

Atlantic salmon (Salmo salar L.) stocks in the Baltic Sea are mainly exploited during their sea migration. The offshore fishery in the feeding grounds of these salmon permitted us to analyse the migrations of certain stocks on the basis of tag recovery data. Four salmon stocks from rivers draining into Bothnian Bay (25°E, 65.5°N) were selected for study. During 1984-1991, about 135 000 2-year-old hatchery-reared smolts were tagged and released. We applied logit models, with the site of recovery as a multicategory response variable, to analyse the distribution of tag recoveries in the Baltic Sea feeding grounds. The results showed the combined influence of stock, prey abundance, and smolt size on the spatial marine distribution of the salmon. Although stock-specific sea migration patterns were apparent, annual environmental factors had a stronger influence on the sea migration route of salmon than did the stock factor. The salmon released as small smolts (total length [Formula: see text] 17.0 cm) were more frequently caught farther from the release site than were those released as larger smolts (>17 cm). The abundance of suitable prey (age 0+ herring) in the year of smolt release was found to be a key factor influencing the migration distance. The salmon released in the years of strong herring recruitment in the Gulf of Bothnia had a higher probability to stay in the Bothnian Sea for feeding and not to migrate farther south.

資源管理型沖合漁業推進総合調査(スルメイカ)の概要について

資源管理型沖合漁業推進総合調査(スルメイカ)の概要について

Optimal Number of Fishing Vessels for Taiwan's Offshore Fisheries: A Comparison of Different Fleet Size Reduction Policies

This study compares the harvest capacity of Taiwan's offshore fishing fleet to sustainable yields of offshore fisheries and evaluates different legislative strategies designed to reduce the fishing fleet. Aggregate offshore fisheries' stock changes and harvest functions are specified and estimated. Results show that the stock has been declining since 1973. Based on dynamic simulations, this study shows that neither the program to restrict the building of new vessels nor a combination of this program with the vessel retirement and buy back program is sufficient to avoid the downward trend in harvests and the deteriorating state of stocks. While reducing fishing effort to the maximum sustainable yield (MSY) level might suffice as an initial vessel reduction measure, attaining MSY within 5 to 10 years seems preferable over a one-year approach. The long-run economic situation would be further improved by an additional reduction of fishing effort to the optimal yield (OY) level.

Valuing Mangrove-Fishery Linkages – A Case Study of Campeche, Mexico

This paper explores the value of mangrove systems as a breeding and nursery habitat for off-shore fisheries, focusing on mangrove-shrimp production linkages in Campeche State, Mexico. We develop an open access fishery model to account explicitly for the effect of mangrove area on carrying capacity and thus production. From the long-run equilibrium conditions of the model we are able to establish the key parameters determining the comparative static effects of a change in mangrove area on this equilibrium. We then estimate empirically the effects of changes in mangrove area in the Laguna de Terminos on the production and value of shrimp harvests in Campeche over 1980–90. Our findings suggest that mangroves are an important and essential input into the Campeche shrimp fishery, but that the low levels of deforestation between 1980 and 1990 mean that the resulting losses to the shrimp fishery are still comparatively small. Over-exploitation of the fishery due to open access conditions remains the more pervasive threat, and without better management any long-run benefits of protecting mangrove habitat are likely to be dissipated.

Modelling interactions between inshore and offshore fisheries: the case of the East China Sea hairtail ( Trichiurus haumela) fishery

Interactions between inshore and offshore fisheries are studied by mathematical modelling. The results show that various components of a fishery interact closely with each other and managing such fisheries must take into account both specific features of each component and interactions between them. To obtain maximum sustainable yields or net revenues, seasonal closure or exclusion of some components may be necessary. In the case of the hairtail fishery in the East China Sea, operation of both trawl fisheries will reduce the total catch. The maximum sustainable yield and maximum net revenue occurs coincidentally when both trawl fisheries are suspended and the fishing mortality in the inshore seine fishery is controlled at F = 1.02. Banning the inshore trawl fishery can increase the total catch without need to raise the efforts of other two components and benefits the inshore seine fishery most significantly. However, above this the fishery remains under pressure unless other components are controlled. Increasing juvenile catches in the inshore seine fishery will lower the total catch and intensify the effect of the two trawl fisheries.

Age at Maturity as a Stress Indicator in Fisheries

years, this fishery provided food and income for the many communities scattered along the east coast of Newfoundland. The Newfoundland fishing industry, based on the annual migration of cod from offshore spawning grounds of the Grand Bank to inshore feeding areas, had been the mainstay of the province's economy (Figure 1). In the 1950s, additional large winter aggregations of cod were located offshore of Newfoundland in water depths of 100-200 fathoms (Johnstone 1977). This discovery prompted the development of a large-trawler offshore fishery, which included foreign vessels, and annual landings increased through the 1960s. By the mid-1970s stock1 size had declined, but it subsequently increased after Canada began to exert control over fishing rights within 200 miles of its coastline on 1 January 1977. (Before 1977 Canada's jurisdiction was limited to within 12 miles of shore). Foreign landings declined over time

Planning annual allocation of fisheries surveillance effort

Fishery surveillance on both of the Atlantic and Pacific coasts of Canada costs the Canadian taxpayer several millions of dollars annually. Few of these dollars are recovered through fines from successfully prosecuted cases involving fishery violations. Consequently, federal fishery surveillance programs are not self-supporting—they are subsidized. In order to reduce the cost of the program to the Canadian taxpayer, it is necessary to implement a cost-effective program which maximizes the deterrent effect of surveillance effort. In this paper we present a tactical linear programming for effectively allocating annual surveillance effort to monitor and control fishing activity, and to enforce fishery regulations in accordance with resource management plans and objectives for the offshore fishery. In particular, we focus on the Atlantic fishery. The tactical model determines on an annual basis, for each of the surveillance units, the amount of effort allocated to each fishery/fishing zone in each time period while maximizing effectiveness. Once the effort allocations are made, operational tasks which involve scheduling surveillance/patrol units on a short-term basis in accordance with the annual plan and current priorities must be completed. We demonstrate the potential use of the planning model.

Multiobjective Bioeconomic Analysis: An Application to the Pacific Whiting Fishery

A multiobjective bioeconomic policy model was developed for the United States Pacific whiting fishery. Pareto-optimal solutions for three policy objectives—rents, production, and female spawning biomass—were developed and analyzed using "hybrid" generating technique. Three policy instruments were considered: harvest quotas, fleet capacity limits, and allocation between shore-based and offshore fisheries. Results indicate that Pareto-optimal allocations to shore-based and at-sea industries will depend on the spatial and temporal characteristics of the stock and the assumptions regarding the harvesting and processing characteristics of each fleet. The analysis also suggests approaches for measuring opportunity costs associated with misidentifying "biological risk", and operationalizing the concept known as "optimum yield".

Modelling economy-ecology linkages in mangroves: Economic evidence for promoting conservation in Bintuni Bay, Indonesia

Woodchip exports pose a potential threat to a 300 000-ha mangrove ecosystem in the Bintuni Bay area of Irian Jaya, Indonesia. The bay supports an important shrimp export industry, and coastal areas support 3000 households. Traditional non-commercial uses of mangroves have an estimated value of Rp20 billion/yr (US$10 million/yr); commercial fisheries are valued at Rp70 billion/yr (US$35 million/yr) and selective commercial mangrove cutting schemes have a maximum value of Rp40 billion/yr (US$20 million/yr). Forest management options, ranging from clear cutting to a cutting ban, are evaluated in a cost–benefit analysis incorporating linkages among mangrove conversion, offshore fishery productivity, traditional uses, and benefits of erosion control and biodiversity maintenance functions. “Linkage scenarios” are developed that reflect potential ecosystem component interactions in Bintuni Bay. Clear cutting is optimal only if linkages are ignored. A cutting ban is optimal if linear and immediate linkages between ecosystem components exist. Under a scenario with linear but delayed linkages of 5 years, selective cutting of 25% of the harvestable mangrove is the optimal strategy; it has a present value of Rp70 billion (US$35 million) greater than the clear cutting option, and more extensive cutting would yield no additional net benefits. Strong economic arguments exist for conservative mangrove clearing. Where strong ecological linkages occur, severe restrictions on clearing activities will be economically optimal. Where ecosystem dynamics are uncertain, programs reducing linkage effects – such as greenbelts, replanting, or selective cutting – will minimise potential economic losses.

Environmental management in Yap, Caroline islands: Can the dream be realized?

Fifty years ago the small developing island states throughout Oceania entertained dreams of achieving economic self-sufficiency and social development. These island states are now beginning to realize the magnitude of their natural resource and environmental management problems and today these dreams seem further from realization than they were at the start. There are many explanations for this, however the causes are not verifiable with scientific methods. Most of these island states have small, fragmented populations leading to dis-economies of scale; and the resources they must manage are, for the most part, wide ranging and diverse and beyond the power of any small political entity to control. The State of Yap in the Federated States of Micronesia is used as an example to explore these problems and some of the mechanisms that are being considered to rectify them. The population of Yap is small but growing; its oceanic waters are still relatively pristine; there is some indication of pollution in Colonia Harbour (surrounding the main shipping port and fisheries complex); education levels of the community are poor and little effort is being made to educate future leaders capable of managing the environment and the marine resources. The chain of responsibility and decision-making within government is hampered by a top-heavy legislative and executive government underlain by a constitutionally enshrined power of veto vested in councils of traditional chiefs. This system lacks the flexibility and education resources needed to respond to the rapidly changing demands now being placed on both the society and the environment. Concern is being expressed in Yap as future sources of foreign aid become less secure. Nevertheless, some efforts are being made to adapt and improve the economic base with emphasis on exploitation of the country's offshore fisheries potential, as well as hopes for aquaculture and small-scale fisheries projects, and the development of agriculture and tourism. The Government recently commissioned a marine resources and coastal management plan which has now been completed. This plan discusses the significant environmental and resource management issues underlying Yap's development objectives, identifies appropriate Government agencies to take responsibility, indicates manpower and training needs and outlines certain legislative changes that may be required. One can, with hindsight, question the application of much foreign aid in the past, as foreign aid without appropriate implementation is wasteful of resources which are in short supply. The need and desirability for continuing foreign aid is without doubt, but responsibility transfer must also accompany technology transfer if it is to truly meet the objectives of aiding the developing nations in the Third World.