Recent Developments in Fisheries Science and Their Prospects for Improving Fisheries Contributions to Food Security

Marine reserves, areas permanently closed to all fishing, are frequently proposed as a tool for managing fisheries. Fishery benefits claimed for reserves include increases in spawning stock size, animal body size, and reproductive output of exploited species. Reserves are predicted to augment catches through export of offspring to fishing grounds, and spillover of juveniles and adults from reserves to fisheries. Protection of stocks and development of extended age structures of populations in reserves are argued to offer insurance against environmental variability and management failure. Models also suggest reserves will reduce year-to-year variability in catches, and offer greater simplicity of management and enforcement. Reserves are predicted to lead to habitat recovery from fishing disturbance which can also enhance benefits to fisheries. Extensive field research confirms many of these predictions. Reserves worldwide have led to increases in abundance, body size, biomass and reproductive output of exploited species. Such measures often increase many times over, sometimes by an order of magnitude or more. Population build up is usually rapid with effects detectable within 2-3 years of protection. Increases are often sustained over extended periods, particularly for longer-lived species and for measures of habitat recovery. Reserves have benefitted species from a wide taxonomic spectrum that covers most economically important taxa, including many species of fish, crustaceans, mollusks and echinoderms. Encouraged by these results, many countries and states have embarked upon initiatives to establish networks of marine reserves. However, reserves remain highly controversial among fishers and fishing industry bodies who argue that fishery benefits remain unproven. In the last three years there has been rapid growth in the number of cases where fisheries have been shown to benefit from reserves. In this report, we critically analyze this body of evidence, drawing upon studies of reserves and fishery closures. Fishery managers have long used fishery closures, areas temporarily closed to fishing for one or more species or to specific fishing gears. They are employed to help rebuild depleted stocks, reduce gear conflicts, protect vulnerable life stages of exploited species or protect sensitive habitats from damaging gears. Such areas can tell us much about the potential effects of marine reserves. Fishery benefits from reserves and fishery closures typically develop quickly, in most cases within five years of their creation. Perhaps the most persuasive evidence of fishery effects of reserves comes from changing fishing patterns. In most places where well-respected reserves or fishery closures exist, fishers tend to move their fishing activities closer to their boundaries. Fishing-the-line, as it is called, allows fishers to benefit from spillover of animals from reserves to fishing grounds. There are now well-documented cases of spillover from more than a dozen countries and including a wide range of species. It is more technically demanding to prove fishery enhancement through export of offspring on ocean currents. Existing reserves are generally small, making it hard to detect increased recruitment to fisheries at a regional scale. However, there are now several cases in which export of eggs and larvae have been confirmed, including dramatic enhancement of scallop fisheries in Georges Bank and clam fisheries in Fiji. Small reserves have worked well and repeatedly produce local benefits. However, regional fisheries enhancement will require more extensive networks of reserves. Some of the most convincing success stories come from places in which between 10 and 35% of fishing grounds have been protected. In several cases there is evidence that yields with reserves have risen to higher levels than prior to protection, despite a reduction in the area of fishing grounds. In other cases, smaller reserves have stabilized catches from intensively exploited fisheries or slowed existing rates of decline. We describe experiences that prove that success of marine reserves is not contingent on habitat type, geographical location, the kind of fishery involved, or the technological sophistication of management. Reserve benefits are not restricted to habitats like coral reefs, or to artisanal fisheries, as some critics claim. Fishery benefits have been demonstrated from reserves established in tropical, warm- and cold-temperate waters, and in many habitats, including coral reefs, rocky reefs, kelp forests, seagrass beds, mangroves, estuaries, soft sediments, continental shelves and deep sea. Reserves and fishery closures have worked well for a wide range of fisheries, spanning recreational fisheries, artisanal fisheries like those of coral reefs, through small-scale nearshore fisheries for species like lobsters, up to industrial-scale fisheries for animals like flatfish and scallops. They have worked across a similarly broad spectrum of management sophistication, from self-policing by committed fishers, through warden patrols to satellite monitoring of distant fishing activities. We now have strong evidence that with the support of local communities, marine reserves offer a highly effective management tool. However, reserves will only rarely be adequate as a stand-alone management approach, although we describe cases where they have worked in the absence of other measures. They will be most effective when implemented as part of a package of limits on fishing effort and protect exploited species and their habitats

Body reserves in intra-African migrants

Avian migration has been shown to be a life history strategy for surviving environmental resource variability, but it requires increased body reserves for long distance flight. Fat reserves make excellent energy stores for barrier crossing, whereas proteins generate less energy for the same mass of fat but provide water during breakdown which may become especially useful when birds become water stressed. Intra-African migrants are probably unlikely to have to cross barriers equivalent to the Sahara and the Mediterranean and so may have different patterns of mass reserves reflecting the utility of metabolizing fat versus protein in hot, tropical environments. We examined differences in proportions of body mass gain, pectoral muscle score and fat score between intra African migrants, Palearctic migrants and resident African species. We tested whether intra-African migrants show a distinct seasonal peak in mass gain corresponding to expected peak migration period in a manner similar to Palearctic migrants, but maintain larger muscle tissues, because Palearctic migrants are more constrained by a need to heavily up regulate fat in addition to fat free reserves before migration due to the energy requirements of crossing the barrier of the Sahara. We found that intra-African migrants had a peak seasonal mass gain similar to Palearctics whereas African residents did not, and that Palearctics increased fat reserves with pectoral muscle reserves, so that they had much higher fat scores for any given level of pectoral muscle compared to intra-African migrants or resident species. Our results suggest that barrier crossing leads to a distinct increase in fat reserves rather than migration per se, and suggests that intra-African migrants are more similar in their reserve management to African residents. Mass gain devoid of visible fat accumulation in intra-African migrants may therefore suggest absence of barriers during migrationPublisher PDFPeer reviewe

Scaling of the risk landscape drives optimal life history strategies and the evolution of grazing

Consumers face numerous risks that can be minimized by incorporating different life-history strategies. How much and when a consumer adds to its energetic reserves or invests in reproduction are key behavioral and physiological adaptations that structure much of how organisms interact. Here we develop a theoretical framework that explicitly accounts for stochastic fluctuations of an individual consumer's energetic reserves while foraging and reproducing on a landscape with resources that range from uniformly distributed to highly clustered. First, we show that optimal life-history strategies vary in response to changes in the mean productivity of the resource landscape, where depleted environments promote reproduction at lower energetic states, greater investment in each reproduction event, and smaller litter sizes. We then show that if resource variance scales with body size due to landscape clustering, consumers that forage for clustered foods are susceptible to strong Allee effects, increasing extinction risk. Finally, we show that the proposed relationship between consumer body size, resource clustering, and Allee effect-induced population instability offers key ecological insights into the evolution of large-bodied grazing herbivores from small-bodied browsing ancestors.Comment: 9 pages, 5 figures, 3 Supplementary Appendices, 2 Supplementary Figure

Development of the body condition score system in Murrah buffaloes: validation through ultrasonic assessment of body fat reserves

The body condition score (BCS) system is a subjective scoring method of evaluating the energy reserves of dairy animals to provide better understanding of biological relationships between body fat, milk production and reproduction. This method helps in adopting the optimum management practices to derive maximum production and maintain optimum health of the livestock. In this study, a new BCS system was developed for Murrah buffaloes. The skeletal check points were identified by studying the anatomical features and amount of fat reserves in slaughtered animals. The scores were assigned from 1 to 5 based on the amount of fat reserves in slaughtered animals. A score of 1 represents least and 5 represents most amount of fat. The skeletal check points identified were ordered based on the amount of carcass fat reserves and scores assigned to prepare a preliminary BCS chart on a 1 to 5 scale at 0.25 increments. The BCS chart was further modified by eliminating the skeletal check points at which the fat reserves were less evident on palpation in most of the buffaloes and a new BCS chart on a 1 to 5 scale at 0.5 increments examining eight skeletal check points was developed. The new BCS system developed was tested for precision in 10 buffaloes for each point of the 1-5 scale by ultrasonographic measurements of body fat reserves. Ultrasonographic measurements showed that as the BCS increased, the amount of fat reserves also increased (p < 0.01), indicating that the BCS adequately reflected the amount of actual fat reserves. BCS was significantly correlated (r = 0.860) with the carcass fat reserves as well as the ultrasonographic fat reserves (r = 0.854)

Trade-offs, condition dependence and stopover site selection by migrating sandpipers

Western sandpipers Calidris mauri on southward migration fly over the Gulf of Alaska to the Strait of Georgia, British Columbia, where they stop for a few days to replenish reserves before continuing. In the Strait, individuals captured on the extensive tidal mudflats of the Fraser estuary (∼25000 ha) are significantly heavier (2.71 g, or >10% of lean body mass) than those captured on the small (<100 ha) mudflat of nearby Sidney Island. Previous work has shown that the difference cannot be attributed to seasonal timing, size, age or gender effects, and here we compare predictions made by six hypotheses about a diverse set of data to explain why, partway through a migratory journey of ∼10000 km, birds have such different body masses at two stopover sites within 40 km of each other. The ‘trade-off’ hypothesis – that the large Fraser estuary offers safety from predators, but a lower fattening rate, while the small Sidney Island site is more dangerous, but offers a higher fattening rate – made six successful predictions, all of which were upheld by the data. All other hypotheses failed at least one prediction. We infer that calidrid sandpipers arriving in the Strait of Georgia with little fat remaining (and therefore low body mass) choose to take advantage of the high feeding rate at small sites like Sidney Island because they are less vulnerable to avian predators than are individuals with higher fat reserves, who instead elect to feed at large open sites like the Fraser estuary mudflats

Changes in plasma biochemistry and body mass during incubation in the Yellow-legged Gull

The >Incubatory Reserves Constancy> hypothesis asserts that incubation could be a departure from breeding stress that allows for the maintenance or recovery of body reserves after laying effort (females) or territory defense (males) in those species with bi-parental incubation such as gulls. The plasma composition and body mass of incubating Yellow-legged Gulls (Larus cachinnans) were analyzed and related to the number of days after egg-laying. Female gulls showed an increase in uric acid and cholesterol levels, whereas males showed only an increase in uric acid values throughout this period. Moreover, females increased while males maintained their body masses. These results could reflect a recovery process after the laying effort supporting the Incubatory Reserves Constancy hypothesis in females. Uric acid and urea levels are positively correlated to body condition in Yellow-legged Gulls, which could be the result of a change in diet composition. This disagrees with recent findings on body composition in incubating gulls and could be related to variations in food availability among populations or years, and could reflect flexibility in the investment devoted by each sex.Peer Reviewe

Biochemical indicators of condition, nutrition and nitrogen excretion in caribou

Urinary urea nitrogen to creatinine ratios, urinary Nt-methylhistidine to creatinine ratios, serum urea nitrogen concentrations (SUN mg/dl), and serum Nt-methylhistidine concentrations were compared with physical measures of body composition in adult female barren-ground caribou (Rangifer tarandus groenlandicus) from the Bathurst and Southampton Island herds during late winter. Body weight and UUC were used to estimate urinary urea nitrogen (urea-N) excretion in free ranging caribou. Only mean UUC reflected differences in fat reserves between populations. None of the biochemical indicators were directly related to body composition. However, elevated UUC were only observed in caribou with depleted fat reserves as demonstrated by low kidney fat index (KFK40) and/or reduced femur marrow fat (FMF&lt;80). UUC greater than 0.25 were indicative of undernourished animals with depleted fat reserves. SUN and UN -MHC showed no clear relationship with fat reserves. The mean estimated daily urea-N excretion for adult female caribou in late winter was extremely low (0.11+0.01SE g urea-N/day, n=76, range=0.011-0.510). The results of my study suggest that UUC can be used to detect nutritionally stressed caribou with depleted fat reserves on lichen winter ranges

Patterns of Nutrient Acquisition in Canvasbacks During Spring Migration

Wetlands used by nesting birds have traditionally been considered the only habitats able to influence natality rates. I examined the potential for body reserves (fat, protein, and calcium) acquired on spring staging areas to be used for reproduction. My objectives were to: 1) describe changes in body reserves during spring, 2) examine alternative uses for body reserves in spring migrants, and 3) identify where reserves are acquired. EXxring spring of 1984 and 198? I collected 151 canvasbacks fAvthva valisineria) at 3 staging areas: Navigation Pool 19 of the Mississippi River; Navigation Pools 7, 8, and 9 of the Mississippi River; and in the prairie pothole region of North Dakota. An additional 28 breeding birds were collected in the aspen parklands of Manitoba. Pair status was determined prior to collection of each bird and all birds were aged. \u27The influence of body size on body reserve levels was corrected where needed. Median collection dates occurred just prior to peak canvasback use of each staging area. Masses of ovaries, testes, oviducts, and the largest follicle diameter increased as spring migration phenology advanced. In late migration, ovary and oviduct masses of paired females were greater than in umpired females. Testes masses of paired and unpaired males did not differ. Among sites, patterns of change in body reserves did not parallel patterns of change in reproductive tissue. Calcium mass of males and females did not di\u27 :er among sites regardless of pair status. Protein reserves of paired, breeding females were larger than those of unpaired migrant females. Paired males in North Dakota had higher protein reserves than did jaired males at Pools 7, 8, and 9 or Erickson. Protein reserves of unpaired males did not differ among various staging areas. Fat masses of males and females varied greatly among sites during\u27 migration bur pair status had little influence on them. Paired females airived on breeding areas fat. Males had. more fat and protein than did fen ales during migration but the opposite was true for breeding females. Flight ranges, estimated from measured levels of stored fat, could not allow canvasbacks at any staging area to fly non-stop to breeding areas and arrive fat. Though fat and prctein reserves are acquired during spring, wetland habitats located closa to breeding areas would more .ikely influence a reproductive effort than would habitats located farther away. Other factors such as the energetic costs of migration and fasting through inclement weather may require birds to stop frequently during migration in order to re-acquire lost reserves. Protection of key staging wetlands scattered along the entire migration route may therefore directly or indirectly influence natality rates of canvasbacks

Breeding limits foraging time : evidence of interrupted foraging response from body mass variation in a tropical environment

Funds were received from the Ubbo Emmius grant, Univ. of Groningen and also from the Univ. of St Andrews.Birds should store body reserves if starvation risk is anticipated; this is known as an ‘interrupted foraging response’. If foraging remains unrestricted, however, body mass should remain low to limit the predation risk that gaining and carrying body reserves entails. In temperate environments mass gain in female birds during breeding is often attributed to egg formation and mass loss after incubation to flight adaptation or the effect of reproductive workload, rather than as a result of an adaptive interrupted foraging response to the limited foraging time or unpredictable foraging conditions that breeding demands. In tropical environments, foraging conditions vary more within the breeding season than in temperate environments, and so studies in tropical environments are more suited to decouple the potentially confounded effects of increase in body reserves versus egg formation on the body mass of breeding birds. In this study, we test whether breeding results in an interrupted foraging response in a tropical savannah system using body mass data collected over a 15-year period from female Common Bulbuls Pycnonotus barbatus. This species breeds both in the wet and dry season, despite fewer resources being available in the dry season. Breeding stage predicted female body mass: body mass peaked abruptly during incubation, but was not closely associated with the egg-laying stage, and declined during brood rearing. Breeding females were heavier in the dry season than in the wet season. In the dry season, heavier birds were more likely to incubate eggs or brood chicks. These observations suggest that increased body reserves are required to buffer the consequence of limited foraging time or impoverished foraging conditions, which may be most pronounced during incubation and in the dry season, respectively. Such mass increases are consistent with an interrupted foraging response, which may apply to temperate zone birds experiencing foraging restrictions during breeding.PostprintPeer reviewe