Designing marine protected areas for migrating fish stocks

This paper extends an earlier analysis and presents an investigation of how migration rates affect the performance of various types of management regimes with respect to economic yield and conservation benefits. Particular emphasis is placed on evaluating the geometric design of marine protected areas (MPAs). Earlier results have shown that MPAs are only likely to provide significant benefits when they are used in conjunction with direct catch or effort controls, unless they are quite large and cover most of the resource in question. Conversely, catch and effort controls are far more effective when protected areas are included in the management regime as a buffer against uncertainty. Dispersal of reproduction (recruitment) to other areas is an important expected benefit of protected areas, but such dispersal increases the variability of the effects of the area protection. If fishing mortality rates outside of the protected area are not controlled then dispersal can result in nullifying some of the benefits of the protected area. Similarly, adult migration increases the variability in the results when an area is protected and critically depends upon an overall control of fishing mortality outside the area. For both dispersal and migration separately or in combination, however, there are clear benefits to using MPAs in conjunction with catch or effort controls. These benefits are expressed in terms of long-term yield and recovery probabilities. In addition, short-term yield declines relatively slowly with increasing area protected. Design of the protected areas is seen to be important since using contiguous areas provide greater protection against overfishing than protected areas in isolation.     

A plan for fisheries management in the lakes drained by the Oulujoki river

Freshwater fishery management is treated as a dynamic system comprising environment protection and improvement, fishing, fishery resources allocation, fish stocking programs and marketing policy. The aims of the plan are to increase the economic value of the catch and to protect the professional fishery. Fisheries statistics, catch per unit effort data and other material were collected during 1972–1976. The total allowable catch (TAC) for the most important fish species was estimated with MSY and population analysis models. The results of fish stockings were studied by tagging and population analysis calculations. Fishing of vendace and non-valuable species (perch, roach, smelt) can be increased, but the fishing pressure on other species should not be raised above the present level. Restrictions on whitefish fishing are needed in some areas. A balanced multispecies fishery is desirable, and suggestions are given for the composition of the fishing gear. Fish stocking can make possible a larger and more valuable catch, but at present its profitability is rather low. The stocking results are strongly affected by the fishery and the gear composition.     

Fishing diseased abalone to promote yield and conservation

Past theoretical models suggest fishing disease-impacted stocks can reduce parasite transmission, but this is a good management strategy only when the exploitation required to reduce transmission does not overfish the stock. We applied this concept to a red abalone fishery so impacted by an infectious disease (withering syndrome) that stock densities plummeted and managers closed the fishery. In addition to the non-selective fishing strategy considered by past disease-fishing models, we modelled targeting (culling) infected individuals, which is plausible in red abalone because modern diagnostic tools can determine infection without harming landed abalone and the diagnostic cost is minor relative to the catch value. The non-selective abalone fishing required to eradicate parasites exceeded thresholds for abalone sustainability, but targeting infected abalone allowed the fishery to generate yield and reduce parasite prevalence while maintaining stock densities at or above the densities attainable if the population was closed to fishing. The effect was strong enough that stock and yield increased even when the catch was one-third uninfected abalone. These results could apply to other fisheries as the diagnostic costs decline relative to catch value.     

On the Optimal Size of Marine Reserves

The excessive and unsustainable exploitation of our marine resources has led to the promotion of marine reserves as a fisheries management tool. Marine reserves, areas in which fishing is restricted or prohibited, can offer opportunities for the recovery of exploited stock and fishery enhancement. This study examines the impact of the creation of marine protected areas, from both economic and biological perspectives. The consequences of reserve establishment on the long-run equilibrium fish biomass and fishery catch levels are evaluated. We include reserve size as control variable to maximize catch at equilibrium. A continuous time model is used to simulate the effects of reserve size on fishing catch. Fish movements between the sites is assumed to take place at a faster time scale than the variation of the stock and the change of the fleet size. We take advantage of these two time scales to derive a reduced model governing the dynamics of the total fish stock and the fishing effort. Simulation results suggest that the establishment of a protected marine reserve will always lead to an increase in total fish biomass, an optimal size of a marine reserve can achieve to maximize the catch at equilibrium.     

Spatial pattern in catch rates: A test of economic theory

Gordon (1953,J. Fish. Res. Bd Can.10, 442–457) used economic theory to predict how catch rates, price and fishing costs should balance in a multi-area, open-access fishery. We use the data from the Tasmanian rock lobster fishery to test this theory. We find that, as prediced by theory, areas with higher monetary and non-monetary costs have consistently higher catch rates than areas with lower costs. We show that this theory also predicts that an increase in price would result in an overall increase in catch rate, and suggest that in fisheries with spatial variation in costs, catch rates may be determined as much by economic factors as biological ones.     

Optimum fishing strategies for Isostichopusfuscus (Echinodermata: Holothuroidea) in the Gulf Of California, Mexico

The Isostichopus fuscus fishery in Mexico was heavily exploited until 1994, when it was closed due to overfishing. However, no information existed on the status of the populations. The fishery was evaluated through an age structured simulation model, and according to our analysis of the stock, the fishery can be feasible and sustainable as long as fishing mortality and age of first catch are optimized. In order to evaluate exploitation strategies, several scenarios were simulated considering different combinations of fishing intensities and ages of first catch. Input data for the model included population parameters, commercial catch and costs and benefits of the fishing operations. Yield production was strongly influenced by the fishing pressure and by the age of first capture. When the first one increased, significant decreases in yield and profits occurred. The best exploitation strategy was these parameters: fishing mortality level F = 0.15, age at first capture t(c) = 4 years, and yielding of approximately 430 tons. However, since the species reproduces for the first time at 5 years, extracting younger specimens would collapse the population. The critical value of fishing mortality was detected at Fc = 0.25. If exceeded, the population tends to exhaustion and the fishery is no longer profitable. In conclusion, I. fuscus fishery is highly vulnerable to overfishing and age of catch. It must be taken into account that the management policies should be considered as pilot and used on a regional basis. Continuous monitoring of the stock, control of the number of fishing licenses and extracting only specimens 5 yeasr-old and older (around 20 cm and >400 g), will allow the populations to recover from fishing activities. Rev. Biol. Trop.     

A comparative study on socio-economic indicators and viability in small-scale fisheries of six districts along the Turkish coast

The study evaluates the status of small-scale fishermen and fishing operations, using socio-economic indicators and economic viability estimates in six selected fishing areas of Turkey during the 2002–2003 fishing season. Fifty-six percent of all small-scale fishing boats investigated achieved a positive net profit, fully recovering their operational and investment costs. Considering the viability of the fishery, 56% can be considered as economically viable. Percentages of negative gross cash flow (GCF) for each of the vessels in the district was 56% in Foça, 57% in Karaburun, 15% in Mordoğan, 16% in Akyaka, 65% in Akçapınar, and 44% in Marmaris. On the other hand, when sustainability is defined with more than an economic performance ratio of 10%, only 41% of the small-scale fishing vessels seem to have shown favourable results. Criteria such as comparatively higher catch, smaller crew size and lower labour costs, structure of the fishery or misreporting might have had a slight role in affecting the overall results which indicate that livelihood and economic viability are threatened by irregular and relatively low income levels in the small-scale fisheries sector. Given the economic conditions of small-scale fishing communities, it is suggested that all persons concerned at the community, industry and government levels should take a fresh look at the problem of sustainability. As such, more attention needs to be paid to the fishery management option by looking at performance data and having long-term monitoring of the socio-economic indicators.     

Predation Risk within Fishing Gear and Implications for South Australian Rock Lobster Fisheries

Depredation of southern rock lobster (Jasus edwardsii) within fishing gear by the Maori octopus (Pinnoctopus cordiformis) has economic and ecological impacts on valuable fisheries in South Australia. In addition, depredation rates can be highly variable resulting in uncertainties for the fishery. We examined how in-pot lobster predation was influenced by factors such as lobster size and sex, season, fishing zone, and catch rate. Using mixed modelling techniques, we found that in-pot predation risk increased with lobster size and was higher for male lobsters. In addition, the effect of catch rate of lobsters on predation risk by octopus differed among fishing zones. There was both a seasonal and a spatial component to octopus predation, with an increased risk within discrete fishing grounds in South Australia at certain times of the year. Information about predation within lobster gear can assist fishery management decision-making, potentially leading to significant reduction in economic losses to the fishery.     

Biodiversity Offsets: A Cost-Effective Interim Solution to Seabird Bycatch in Fisheries?

The concept of biodiversity offsets is well established as an approach to environmental management. The concept has been suggested for environmental management in fisheries, particularly in relation to the substantial numbers of non-target species--seabirds in particular--caught and killed as incidental bycatch during fishing activities. Substantial areas of fisheries are being closed to protect these species at great cost to the fishing industry. However, other actions may be taken to offset the impact of fishing on these populations at lower cost to the fishing industry. This idea, however, has attracted severe criticism largely as it does not address the underlying externality problems created by the fishing sector, namely seabird fishing mortality. In this paper, we re-examine the potential role of compensatory mitigation as a fisheries management tool, although from the perspective of being an interim management measure while more long-lasting solutions to the problem are found. We re-model an example previously examined by both proponents and opponents of the approach, namely the cost effectiveness of rodent control relative to fishery area closures for the conservation of a seabird population adversely affected by an Australian tuna fishery. We find that, in the example being examined, invasive rodent eradication is at least 10 times more cost effective than area closures. We conclude that, while this does not solve the actual bycatch problem, it may provide breathing space for both the seabird species and the industry to find longer term means of reducing bycatch.     

Use of dolphins and caimans as bait for Calophysus macropterus (Lichtenstein, 1819) (Siluriforme: Pimelodidae) in the Amazon

A new fishery has been developing in the Amazon that uses dolphin and caiman species as bait to catch piracatinga (Calophysus macropterus), having thus the potential to cause adverse food‐web impacts; however a lack of basic understanding of this fishery is a limitation to the necessary management action. Interviews with fishers and analyses of fishing records in Brazil were used for the study, including harvest methods, types of baits used, commercialization chains, and the rate of increase of piracatinga yields in recent years. Piracatinga fishers are subsistence fishers who harvest piracatinga as a means to alleviate economic constraints when the catch of other species is not profitable or banned due to (reproductive) closed seasons. Harvesting is done with wooden and nylon crates and cages in which whole or pieces of caimans and dolphins are placed to attract the piracatinga, entrapping them. The piracatinga are then sold to intermediate sellers for resale to a few large fish freezing and processing plants for export to Colombia. Annual piracatinga yields in the study area increased at an average rate of 446.5% per year, from 865 kg in 2003 to 23 176 kg in 2009. Because dolphins and caimans comprise various endangered species, the Brazilian government has recently implemented a ban on this fishery, which can be enforced at fish freezing and processing plants. However, there is a danger that such enforcement will lead to the development of a geographically dispersed chain of commercialization and export, such as currently exists for other species including caimans, which would be impossible to control.     

Quantifying the Short-Term Costs of Conservation Interventions for Fishers at Lake Alaotra,Madagascar

Artisanal fisheries are a key source of food and income for millions of people, but if poorly managed, fishing can have declining returns as well as impacts on biodiversity. Management interventions such as spatial and temporal closures can improve fishery sustainability and reduce environmental degradation, but may carry substantial short-term costs for fishers. The Lake Alaotra wetland in Madagascar supports a commercially important artisanal fishery and provides habitat for a Critically Endangered primate and other endemic wildlife of conservation importance. Using detailed data from more than 1,600 fisher catches, we used linear mixed effects models to explore and quantify relationships between catch weight, effort, and spatial and temporal restrictions to identify drivers of fisher behaviour and quantify the potential effect of fishing restrictions on catch. We found that restricted area interventions and fishery closures would generate direct short-term costs through reduced catch and income, and these costs vary between groups of fishers using different gear. Our results show that conservation interventions can have uneven impacts on local people with different fishing strategies. This information can be used to formulate management strategies that minimise the adverse impacts of interventions, increase local support and compliance, and therefore maximise conservation effectiveness.     

Rights-based Fisheries Management: An Environmentalist Perspective

Fisheries management regimes take many forms, but most fail to designate shares of the catch. This failure creates strong incentives for individuals to maximize their share without regard to long-term sustainability, because the benefits of conservation actions do not accrue to individuals. The competition to maximize catch usually entails excessive capital investments in fishing vessels and gear and intense fishing pressure, resulting in overfishing, high bycatch rates, and the use of large, efficient types of gear that can harm habitat. Managers respond by increasing regulations, but this often exacerbates perverse incentives. In addition, many fisheries could be producing more value than the current system permits, i.e. large quantities of fish are landed during short seasons, forcing fishermen to sell for low prices. Conservation and economic problems facing fisheries can be addressed in an integrated way, by designating access privileges (specifying shares of the catch) to individuals, harvest cooperatives, fishing sectors, communities, or other appropriate entities. Designated Access Privilege (DAP) systems demonstrably end the competition to maximize catch and often result in better conservation and financial performance. The cost of implementing these systems can be relatively high and has been a barrier to better management. However, this doesn’t have to be so. Fisheries could accept investments from a variety of sources and use a portion of the increased financial performance to repay recoverable grants and loans. The key to protecting fish stocks, habitats, and the communities that depend on them will be to implement DAPs that are appropriate for each fishery or community, making investments in sustainability, and creating financing mechanisms that are themselves sustainable, drawing on the increased value that DAP fisheries can produce.     

Assessing the risk of alternative management strategies in a Mediterranean fishery: protecting the younger vs reducing fishing effort

A stochastic age-structured population model was developed to explore biologically favourable levels of effort and closing periods within the sardine pelagic fishery in the eastern Mediterranean Sea. Results suggested that the developed age-structured model captured the observed biomass fluctuations and catches reasonably well and represents the first comprehensive investigation of alternative management strategies for eastern Mediterranean sardine fishery that include stochasticity. The present study provided direct evidence for the importance of the correct timing of the temporal fishing ban. Significant benefits were found both in terms of biomass and catch from a corrective shift in the fishing closed period. The current findings suggested that protecting the younger age groups from fishing in the period October–December, by shifting the ban period earlier than December may profit, biologically, the stock and economically the fishing sector. Progressive reductions in fishing mortality/effort also yield significant positive biological and fishery benefits in the short term.     

Small-scale manjuba fishery around Cardoso Island State Park, SP, Brazil.

This work was carried out in the Enseada da Baleia and Vila Rápida communities. Data was provided by the Co-Management Committee of the Cardoso Island State Park (PEIC) on manjuba fishery management, technique and strategies used by the fishermen, as well as locally accumulated knowledge. Based on the results, social, ecological, and economic aspects of this type of fishing were analyzed. The importance of the accumulated knowledge and experience of this community, as well as the limitations imposed by local fishing gear, was concluded to be essential in conserving manjuba fishery conditions in the area. Industrial fishing, relevant state legislation, and market conditions were found to be the main obstacles to local fishery. Various proposals are suggested for manjuba fishery management, with emphasis on the need for fishing community participation in whatever measures are ultimately implemented.     

The state of exploitation of the commercial demersal fishery of Cameroon

The state of exploitation of the demersal fisheries resources of Cameroon has been assessed using the classic Schaefer's (1954) model and the Gulland'ss (1961) moving average. The euilibrium yield found with the Schaefer method is statistically different (95 % probability) and higher than the Gulland approach. Because equilibrium models consistently over-estimate MSY and its related optimum effort, management option should target the 95 % value of the estimated parameters. The resources are being over-fished; as an immediate alternative to the urgent concern, catch and/or effort quotas could be allocated to the various fishing companies, with the total allocated catch and/or effort (for all fishing companies) 5% less than the estimated parameters. Enforcement control of that policy would be simplified as fishing activities are localised in the two main estuaries of the “Cameroon River” and Riodel-Rey;results should be complemented by economic studies of the fishery, as these economic factors would explain or better predict the behaviour of the fishing industry.     

Catch estimation in the presence of declining catch rate due to gear saturation

One strategy for estimating total catch is to employ two separate surveys that independently estimate total fishing effort and catch rate with the estimator for total catch formed by their product. Survey designs for estimating catch rate often involve interviewing the fishermen during their fishing episodes. Such roving designs result in incomplete episode data and characteristically have employed a model in which the catch rate is assumed to be constant over time. This article extends the problem to that of estimating total catch in the presence of a declining catch rate due, e.g., to gear saturation. Using a gill net fishery as an example, a mean-of-ratios type of estimator for the catch rate together with its variance estimator are developed. Their performance is examined using simulations, with special attention given to effects of restrictions on the roving survey window. Finally, data from a Fraser River gill net fishery are used to illustrate the use of the proposed estimator and to compare results with those from an estimator based on a constant catch rate.     

Estimating the impact of interactions between bottlenose dolphins and artisanal fisheries around the Balearic Islands

Interactions between marine mammals and fisheries are a growing problem, and effective management requires assessment of the factors driving the interaction and of the impacts on fisheries. We used data from interactions between artisanal fisheries and bottlenose dolphins around the Balearic Islands to assess these factors and impacts. Observers collected data during 1,040 fishing operations over 3 yr. Location and year were important factors affecting interaction probability, with some areas showing large increases over the study period. We estimated the combined cost of catch loss and net damage as 6.5% of the total catch value (95% CI ?12.3%, ?1.6%), and the annual loss to be 3.4% (95% CI ?6.5%, ?0.1%) of the total catch by weight. This weight equates to the dietary needs of ～12 dolphins (95% CI 0.2, 22), suggesting the fishery is not a vital food source for the dolphin population. Two dolphins died through entanglement during the observed fishing operations. We observed 3% of the total fishing activity, by weight, in 2003; scaling up this mortality directly suggests that as many as sixty dolphins may be dying in nets each year. This interaction likely has serious conservation implications for the dolphin population.     

A BAYESIAN ANALYSIS TO ESTIMATE LOSS IN SQUID CATCH DUE TO THE IMPLEMENTATION OF A SEA LION POPULATION MANAGEMENT PLAN

This study estimates the effect of a sea lion ( Phocarctos hookeri ) population management plan on both the sea lion population and the associated squid ( Nototodarus sloanii ) fishery. The goal of the management plan is to rebuild the sea lion population and involves closing the squid fishery when a threshold level of sea lions have been caught. The threshold level is calculated from a generalized simulation analysis which conservatively allows for adequate population rebuilding for a number of different species and populations. Our analysis uses Bayesian theory to describe uncertainty in the sea lion population site and squid catch under the implementation of the management plan. The priors represent this particular sea lion population, and the analysis represents expectation rather than calculating conservative levels of safe fishing-related mortality. The results show that the squid catch is very sensitive to whether or not the squid fishery is closed when it exceeds the threshold level for sea lion bycatch. The sea lion population size is much less sensitive to the closure of the squid fishery. For an economically important fishery, the estimates of uncertainty in both loss of catch and increase in sea lion population are needed to allow informed decision-making about trade-offs between sea lion conservation and full exploitation of the fishery.     

Effect of Small Versus Large Clusters of Fish School on the Yield of a Purse-Seine Small Pelagic Fishery Including a Marine Protected Area

We consider a fishery model with two sites: (1) a marine protected area (MPA) where fishing is prohibited and (2) an area where the fish population is harvested. We assume that fish can migrate from MPA to fishing area at a very fast time scale and fish spatial organisation can change from small to large clusters of school at a fast time scale. The growth of the fish population and the catch are assumed to occur at a slow time scale. The complete model is a system of five ordinary differential equations with three time scales. We take advantage of the time scales using aggregation of variables methods to derive a reduced model governing the total fish density and fishing effort at the slow time scale. We analyze this aggregated model and show that under some conditions, there exists an equilibrium corresponding to a sustainable fishery. Our results suggest that in small pelagic fisheries the yield is maximum for a fish population distributed among both small and large clusters of school.     

Applying Fishers' ecological knowledge to construct past and future lobster stocks in the Juan Fernández Archipelago, Chile

Over-exploited fisheries are a common feature of the modern world and a range of solutions including area closures (marine reserves; MRs), effort reduction, gear changes, ecosystem-based management, incentives and co-management have been suggested as techniques to rebuild over-fished populations. Historic accounts of lobster (Jasus frontalis) on the Chilean Juan Fernández Archipelago indicate a high abundance at all depths (intertidal to approximately 165 m), but presently lobsters are found almost exclusively in deeper regions of their natural distribution. Fishers' ecological knowledge (FEK) tells a story of serial depletion in lobster abundance at fishing grounds located closest to the fishing port with an associated decline in catch per unit effort (CPUE) throughout recent history. We have re-constructed baselines of lobster biomass throughout human history on the archipelago using historic data, the fishery catch record and FEK to permit examination of the potential effects of MRs, effort reduction and co-management (stewardship of catch) to restore stocks. We employed a bioeconomic model using FEK, fishery catch and effort data, underwater survey information, predicted population growth and response to MR protection (no-take) to explore different management strategies and their trade-offs to restore stocks and improve catches. Our findings indicate that increased stewardship of catch coupled with 30% area closure (MR) provides the best option to reconstruct historic baselines. Based on model predictions, continued exploitation under the current management scheme is highly influenced by annual fluctuations and unsustainable. We propose a community-based co-management program to implement a MR in order to rebuild the lobster population while also providing conservation protection for marine species endemic to the Archipelago.