Application of marine reserves to reef fisheries management

Abstract Establishing permanent ‘no-take’ marine reserves, areas where fishing and all other extractive activities are prohibited, is an attractive but under-utilized tool for fisheries management. Marine reserves could potentially deal with many fishery problems that are not effectively addressed by other traditional management measures; they also offer numerous social, economic, and scientific benefits not directly related to fisheries. Limited but growing research has shown beneficial biological and economic effects of marine reserves on fisheries. More research is needed, especially at larger scales, to determine the ideal marine reserve size, number and location necessary to optimize fisheries productivity and resource conservation. Sufficient evidence is available to justify the expanded use of marine reserves in an adaptive approach to fisheries management.     

The role of marine reserves in achieving sustainable fisheries

Many fishery management tools currently in use have conservation value. They are designed to maintain stocks of commercially important species above target levels. However, their limitations are evident from continuing declines in fish stocks throughout the world. We make the case that to reverse fishery declines, safeguard marine life and sustain ecosystem processes, extensive marine reserves that are off limits to fishing must become part of the management strategy. Marine reserves should be incorporated into modern fishery management because they can achieve many things that conventional tools cannot. Only complete and permanent protection from fishing can protect the most sensitive habitats and vulnerable species. Only reserves will allow the development of natural, extended age structures of target species, maintain their genetic variability and prevent deleterious evolutionary change from the effects of fishing. Species with natural age structures will sustain higher rates of reproduction and will be more resilient to environmental variability. Higher stock levels maintained by reserves will provide insurance against management failure, including risk-prone quota setting, provided the broader conservation role of reserves is firmly established and legislatively protected. Fishery management measures outside protected areas are necessary to complement the protection offered by marine reserves, but cannot substitute for it.     

Larval export from marine reserves and the recruitment benefit for fish and fisheries

Marine reserves, areas closed to all forms of fishing, continue to be advocated and implemented to supplement fisheries and conserve populations. However, although the reproductive potential of important fishery species can dramatically increase inside reserves, the extent to which larval offspring are exported and the relative contribution of reserves to recruitment in fished and protected populations are unknown. Using genetic parentage analyses, we resolve patterns of larval dispersal for two species of exploited coral reef fish within a network of marine reserves on the Great Barrier Reef. In a 1,000 km(2) study area, populations resident in three reserves exported 83% (coral trout, Plectropomus maculatus) and 55% (stripey snapper, Lutjanus carponotatus) of assigned offspring to fished reefs, with the remainder having recruited to natal reserves or other reserves in the region. We estimate that reserves, which account for just 28% of the local reef area, produced approximately half of all juvenile recruitment to both reserve and fished reefs within 30 km. Our results provide compelling evidence that adequately protected reserve networks can make a significant contribution to the replenishment of populations on both reserve and fished reefs at a scale that benefits local stakeholders.     

Underwater acoustics in marine fisheries and fisheries research

Underwater acoustics enables the detection and precise location of fish and is therefore a prerequisite for effective fishing methods such as pelagic trawling and purse seining. The application of acoustic instruments to detect fish and monitor gear performance in modern commercial fisheries is outlined. The latest developments in obtaining information such as bottom roughness and determining such characteristics of fish detected as size and species are presented.Echo integration is now widely used to estimate the abundance of commercially important fish stocks. The principles of the method are outlined briefly, and special emphasis is put on such effects of fish behaviour as the dramatic influence of fish orientation on its backscattering cross section, the possible effects of vessel avoidance, and the uncertainties connected with spatial variability.The use of acoustic tags, echosounders and sonar to study and quantify fish behaviour and distribution is outlined, with particular attention to new developments that provide detailed information on fish behaviour and distribution in relation to environmental parameters.Future developments and improvements in the application of underwater acoustics to commercial fisheries and fisheries research are suggested     

53 A Seaweed's perspective on marine reserves

In response to major changes in coastal ecosystems in recent decades, a number of governmental agencies around the world are establishing marine reserves – areas where removal of animals or plants is prohibited. Although marine reserves are touted as an ecosystem based approach to management of marine resources, the vast majority of attention on reserve design and impact focuses solely on fish. Although a few species of algae are commercially harvested, most are not. As a result, they will receive little direct benefit from protection by reserves aside from habitat protection. From the perspective of a seaweed, the primary impacts of marine reserves will therefore be indirect through species interactions. We examine the rapidly growing theoretical and empirical literature on marine reserves to anticipate the likely responses of seaweeds to exclusion of fishing. The key issues that emerge are: the trophic level of prior fishing and the dispersal scales of seaweeds relative to their competitors and consumers. The latter issue is poorly understood and poses a key challenge to phycologists if we are to effectively incorporate seaweeds into future marine reserve design.     

Comparative size and composition of yield from six Fijian reef fisheries

The size and composition of finfish yield from six Fijian reef fisheries was determined using catch records from a voluntary logbook scheme. A total of 172 logbooks were issued for 30-day periods in October 1992 and February and June 1993 and they provided information on 1369 fishing trips. Catch records were weighted, using the results of contemporaneous fishing activity and fleet size surveys, to provide yield estimates for each fishing ground ( qoliqoli ). Yield from all qoliqoli was dominated by Serranidae and Lethrinidae which were favoured for consumption and sale. Yields were expressed on the basis of reef area for fish from different trophic groups. Macroinvertebrate-feeders and piscivores accounted for more than half the yield in all qoliqoli and there were significant differences in area specific yield between qoliqoli. There was no evidence of fishers adopting more powerful fishing techniques or catching fish from lower trophic levels in order to maintain yield from any qoliqoli. This suggested that the fisheries examined were all capable of sustaining the reported yields of up to 3.4 tonne km⁻² qoliqoli year ⁻¹ or 10.2 tonne km⁻² coral reef year ⁻¹ and that in sites where yields were less they might be increased sustainably.     

Spillover from marine reserves related to mechanisms of population regulation

Spillover of fish from marine reserves to adjacent harvested waters may be mediated by density-independent movement, density-dependent movement, or both. If dispersal is by random movement, populations within the reserve must be regulated by density-dependent population growth (DDG). Density-dependent movement (DDM) can also regulate the population if accelerated emigration from a reserve to the surrounding fishing grounds leads to substantially increased mortality. Using spatially explicit models, we show that stock per unit area is bounded for DDG and increases with size for DDM. With DDG, spillover rate per unit area of reserve is maximized with reserves around 50% larger in linear dimension than the minimum size for population persistence. With DDM, spillover per unit area of reserve increases with reserve size. The results highlight the need for the mechanism of population regulation to be incorporated into theoretical and empirical investigations of marine reserve ecology.     

Patterns and prediction of population recovery in marine reserves

Marine reserves (no-take zones) are widely recommended asconservation and fishery management tools. One potential benefitof marine reserves is that they can reduce fishing mortality.This can lead to increases in the abundance of spawners,providing insurance against recruitment failure and maintainingor enhancing yields in fished areas. This paper considers thefactors that influence recovery following marine reserveprotection, describes patterns of recovery in numbers andbiomass, and suggests how recovery rates can be predicted.Population recovery is determined by initial population size, theintrinsic rate of population increase r, and the degree ofcompensation (increases in recruits per spawner as spawnerabundance falls) or depensation (lower than expected recruitmentat low abundance, Allee effect) in the spawner-recruitrelationship. Within a reserve, theoretical recovery rates arefurther modified by metapopulation structure and the success ofindividual recruitment events. Recovery also depends on theextent of reductions in fishing mortality (F) as determined bythe relationship between patterns of movement, migration, anddensity-dependent habitat use (buffer effect) in relation to thesize, shape and location of the reserve. The effects ofreductions in F on population abundance have been calculatedusing a variety of models that incorporate transfer rates betweenthe reserve and fished areas, fishing mortality outside thereserve and life history parameters of the population. Thesemodels give useful indications of increases in production andbiomass (as yield per recruit and spawners per recruitrespectively) due to protection, but do not address recruitment.Many reserves are very small in relation to the geographicalrange of fish or invertebrate populations. In these reserves itmay be impossible to distinguish recovery due to populationgrowth from that due to redistribution. Mean rates of recoverycan be predicted from r, but the methods are data intensive. Thisis ironic when marine reserves are often favoured for managementor conservation in data-poor situations where conventional stockassessment is impossible. In these data-poor situations, it maybe possible to predict recovery rates from very low populationsizes by using maximum body size or age at maturity as simplecorrelates of the intrinsic rate of natural increase.     

Exploited marine invertebrates: genetics and fisheries

The application of genetic techniques to invertebrate fisheries is in many ways essentially similar to that in vertebrate (i.e. finfish) fisheries, for which there is already an extensive body of published data. However, there are also relative differences which lead to particular problems in the use of genetic data to study commercially important invertebrate species. The main role for genetics of both vertebrates and invertebrates has been, and is likely to continue to be, the identification of groups of interbreeding individuals as the basis for a fishery. It is in the identification of the breeding unit that the genetic differences between vertebrates and invertebrates can be of practical significance. The genetic breeding unit, usually called a 'stock' in fisheries biology, generally shows a certain uniformity of size in most marine fish which have been studied. Smaller or less mobile fish (e.g. flatfish) may only range a few tens of kilometres to their breeding grounds, whilst in more mobile, particularly migratory pelagic species (e.g. Scombridae), the area occupied by a stock is likely to be far greater and for a few (e.g. large pelagic elasmobranchs), a single unit of stock may be almost circumglobal. However, marine fish generally, particularly those large or plentiful enough to be of commercial interest, are likely to be fairly mobile and in many cases the order of mobility is likely to be in the region we might predict from our knowledge of the biology and habits of the species. In the genetic assessment of `stocks' for invertebrate fisheries, we face a number of additional problems, mostly related to the large evolutionary range of invertebrates exploited and their widely different biology. Although in Europe and North America marine invertebrate fisheries may be thought of as being mainly for decapod crustaceans and bivalve molluscs, globally commercially important marine invertebrate fisheries range from sponges to squid and include such diverse groups as sea cucumbers, barnacles, krill, octopuses, cuttlefish, sea anemones, ascidians, polychaetes, sea urchins, gastropods and jellyfish. An obvious feature of many of these invertebrates is that the adult (i.e. commercial) stage of the life cycle is sessile (e.g. barnacles, sponges, ascidians) or of very limited mobility (e.g. sea anemones, sea urchins, bivalves, gastropods), with the result that the dispersive phase of the life cycle is the larva. Other groups (e.g. krill, jellyfish) are planktonic or nektonic and may cover very large distances, but, unlike fish, have little control over the distance or direction of travel, whilst some of the open ocean pelagic squid are more mobile than most fish and may migrate thousands or kilometres to spawning grounds. The very low mobility of both larva and adult in some invertebrates indicates that dispersal, and hence stock size, is likely to be low and that, therefore, stocks are far more vulnerable to overfishing than in most fish species. An additional difficulty is that genetic studies to date indicate a remarkably high incidence of cryptic speciation in marine invertebrates, sometimes even in comparatively well studied commercially important species. Thus, although to date marine invertebrate fisheries have not received the same level of attention from geneticist as finfish fisheries, it is clear that for invertebrate fisheries genetic data are relatively far more important if a fishery is to be exploited without being endangered.     

Marine ecology: reserves do have a key role in fisheries

A new study of the Great Barrier Reef proves a 100-year old conjecture correct: marine reserves do replenish populations in surrounding fishing grounds, while modern reserve networking theory is validated by exchange of offspring of animals among protected areas.     

Connectivity, sustainability, and yield: bridging the gap between conventional fisheries management and marine protected areas

A substantial shift toward use of marine protected areas (MPAs) for conservation and fisheries management is currently underway. This shift to explicit spatial management presents new challenges and uncertainties for ecologists and resource managers. In particular, the potential for MPAs to change population sustainability, fishery yield, and ecosystem properties depends on the poorly understood consequences of three critical forms of connectivity over space: larval dispersal, juvenile and adult swimming, and movement of fishermen. Conventional fishery management describes the dynamics and current status of fish populations, with increasing recent emphasis on sustainability, often through reference points that reflect individual replacement. These compare lifetime egg production (LEP) to a critical replacement threshold (CRT) whose value is uncertain. Sustainability of spatially distributed populations also depends on individual replacement, but through all possible paths created by larval dispersal and LEP at each location. Model calculations of spatial replacement considering larval connectivity alone indicate sustainability and yield depend on species dispersal distance and the distribution of LEP created by species habitat distribution and fishing mortality. Adding MPAs creates areas with high LEP, increasing sustainability, but not necessarily yield. Generally, short distance dispersers will persist in almost all MPAs, while sustainability of long distance dispersers requires a specific density of MPAs along the coast. The value of that density also depends on the uncertain CRT, as well as fishing rate. MPAs can increase yield in areas with previously low LEP but for short distance dispersers, high yields will require many small MPAs. The paucity of information on larval dispersal distances, especially in cases with strong advection, renders these projections uncertain. Adding juvenile and adult movement to these calculations reduces LEP near the edges in MPAs, if movement is within a home-range, but more broadly over space if movement is diffusive. Adding movement of fishermen shifts effort on the basis of anticipated revenues and fishing costs, leading to lower LEP near ports, for example. Our evolving understanding of connectivity in spatial management could form the basis for a new, spatially oriented replacement reference point for sustainability, with associated new uncertainties.     

A framework for assessing the biodiversity and fishery aspects of marine reserves

1.  Resource management agencies are often charged with managing natural resources for economic and social goals, while also protecting and conserving biodiversity and ecosystem function. However, this may not always be possible. Ecosystem-based management is frequently suggested as a way to achieve multiple objectives in resource management and requires that trade-offs among conflicting objectives be identified and an effective means to utilize these trade-offs developed.
2.  We examine the relationship between area and species richness in a diverse assemblage of fishes along the US West Coast and then use parameters from this relationship as input for a model that considers trade-offs between fisheries yield and the number of species protected by different management strategies.
3.  The species–area relationship ( S  =  cA ^z ) for fishes along the US Pacific coast is well described by the relationship S  =   16·18 A ^0·226.
4.  There are nearly linear trade-offs between diversity and yield when fishing effort is low. However, the trade-offs become nonlinear as fishing effort increases and imposing MPAs increases both the conservation and fisheries value of the system when the system is overfished.
5.   Synthesis and applications . Solving conflicts between fisheries and conservation requires attention as to how conservation benefits accrue as fishing effort is reduced. However, scientists often lack quantitative information about the trade-offs inherent in human activities such as fisheries. The approach we develop here can begin to help frame the questions to be posed and evaluate the likely consequences of different management options.     

Spatial population dynamics and the design of marine reserves

The failure of many fisheries world-wide, and the concern about marine biodiversity, has sparked a growing interest in the spatial aspects of harvested populations. If a population conforms to the Ideal Free Distribution and that one of the habitats is set aside as a reserve free from harvesting, the design of reserves may be problematic. If a substantial proportion of the unharvested population is to be preserved, then the reserve area must be unrealistically large, or have a much higher expected fitness than the unprotected area. Interestingly, the optimal harvest rate will be unaffected by both the size of the reserve and the quality of it relative to the harvested area. Even if the Ideal Free Distribution model is extended to include simple age-structure and "spillover" of recruits from the reserve, these conclusions largely remain intact. In a model that also includes spillover, the habitat quality of the reserve may also affect the catch.     

Density dependence and the economic efficacy of marine reserves

Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra- or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter- or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Decadal-scale rebuilding of predator biomass in Philippine marine reserves

No-take marine reserves (NTMRs) provide hope that local carrying capacity may be partially restored if reserves are protected long enough. How long is long enough? We assess the duration of protection required for populations of large predatory reef fish in marine reserves to attain new steady states. We monitored biomass of large predatory fish in two marine reserves at Sumilon and Apo Islands, Philippines, almost annually for 26 years (1983–2009), and fit a logistic model to the data. As duration of reserve protection increased, biomass of predatory fish approached an asymptote, although the models suggest that 20–40 years of protection is required to attain new steady states. Thus, for local carrying capacity to be rebuilt, no-take protection must be effective on decadal timescales.     

Dynamics of artisanal fisheries in two Brazilian Amazonian reserves: implications to co-management

In this study we compare the dynamics of artisanal fishery in two adjacent reserves located in the Brazilian Amazon, Mamirauá (being managed for more than 12 years) and Amanã (initiating a management process), through the record of 485 fish landings in one fishing community in each reserve during high and low water seasons in 2003. Our goals were, first, to make a rapid and comparative assessment of some main aspects of fisheries in these two communities (fish species caught, CPUE, fishing gear and habitats exploited). Second, we used such data to evaluate if management strategies already in place in Mamirauá would be also valid for Amanã. Third, we compared fishing CPUE between the two communities, in order to check if co-management measures have contributed, at least partially, to preclude over-fishing, maintaining a higher fishing reward in Mamirauá reserve. We analyzed fisheries directed to the two most important marketable fishes in the region: the pirarucu (Arapaimas gigas) and the tambaqui (Colossoma macropomum), besides those fisheries aimed to subsistence and lower valued fishes. Our results indicated that the tambaqui was intensively fished year-round in Mamirauá, while Amanã fishers caught a higher variety of fishes, including catfishes and migratory scale fishes. Such differences might reflect differences in gear used and habitat exploited by fishers during the high water season. Mamirauá fishers caught a higher fish biomass considering both marketable and all fishes. Differences in gear used, habitats exploited and fishes caught during high water season indicate that distinct management initiatives might apply for each reserve. Notwithstanding their differences, both communities exploited the commercial fishes (tambaqui and pirarucu) in a similar way during the low water season. Therefore, the higher mean fishing yield (CPUE) observed in Mamirauá may be partially attributable to co-management measures, considering that Mamirauá has possibly been experiencing a higher fishing intensity than Amanã. Fishing related data are seldom available in Brazil and other tropical developing countries. We thus provided a framework of fast assessment of fishing dynamics, which may represent a first and useful step for management initiatives in the absence of more detailed data.     

Bycatches of endangered,threatened and protected species in marine fisheries

Bycatch remains one of the most significant fisheries issues in the world and its monitoring and reporting is now expected in many regions. This paper provides a global synthesis of the data that are available on one of the most controversial components of bycatch, that associated with the capture and discarding of endangered, threatened and protected (ETP) species in marine commercial and artisanal fisheries. We examine the available literature regarding estimates for the key taxa in this category of bycatch (seabirds, turtles, sea snakes, marine mammals, sharks, rays and teleosts) and use the data to try to provide a total global estimate. We estimate (albeit quite imprecisely) that at least 20 million individuals of such species are discarded annually throughout the world. However, there remain far too many gaps and uncertainties across fisheries and regions in the information to provide any robustness (or variance) around such an estimate, nor to determine the actual fates of these animals (many may survive). This is exacerbated because: (1) the occurrences of such species are often rare and controversial and so go either unnoticed and/or unrecorded; (2) different levels of protection are afforded to different ETP species in different countries and fisheries and; (3) discarding practices vary greatly across a hierarchy of spatio-temporal scales and according to individual fishing conditions and procedures—the latter affecting actual mortalities. Nevertheless, there have been major initiatives established in recent years to provide better data on such interactions in addition to novel fishing methods and practices that reduce them and also improve the survival of discarded individuals. This paper discusses the data currently available and the quite significant gaps that remain.