Time-area Closures Research Articles

Evaluation of Alternatives to Winter Closure of Black Sea Bass Pot Gear: Projected Impacts on Catch and Risk of Entanglement with North Atlantic Right Whales Eubalaena glacialis

AbstractTime–area closures have been widely used in fisheries management to prevent overfishing and reduce the bycatch of protected species. Due to quota overages and concerns about entanglement of federally protected North Atlantic right whales Eubalaena glacialis, the commercial harvest of Black Sea Bass Centropristis striata using pot gear has been prohibited in the southeastern United States in winter since 2009. Following the rebuilding of the Black Sea Bass stock and a change to the start date of the fishing year, the South Atlantic Fishery Management Council (SAFMC) increased the commercial annual catch limit (ACL) and is considering twelve alternatives to the pot gear closure that would revise the timing and/or spatial extent of the closure. Changes to this closure could affect the annual catch of Black Sea Bass and increase the risk of right whale entanglement in pot gear. Using historical fishing effort, landings, and right whale sightings data, we projected Black Sea Bass landings and the relative risk of right whale entanglement for each closure alternative, expressed in relative risk units (RRU). We predict that the ACL would be caught, resulting in an in‐season closure for most of the proposed SAFMC closure alternatives. The relative risk of entanglement, estimated from the spatial and temporal overlap of Black Sea Bass pot gear fishing effort and right whale relative abundance, was lower for some alternatives than for others, and the relative differences between alternatives were consistent among uncertainty scenarios. The SAFMC's preferred alternative is projected to result in a relatively low increase in risk to North Atlantic right whales (3–15 RRU off North Carolina and 1–12 RRU off Florida–South Carolina). This framework demonstrates the use of temporally dynamic spatial overlays in assessing the impacts of time–area closures with multiple objectives.Received April 23, 2015; accepted January 15, 2016

Using Ostrom's common-pool resource theory to build toward an integrated ecosystem-based sustainable cetacean tourism system in Hawai`i

This paper explores the suitability of community-based conservation measures to complement a proposed command-and-control approach for two multi-user bays with spinner dolphins in Hawai`i, USA, which have considerable dolphin watching tourist activities and human–dolphin interactions. The paper uses Ostrom's common-pool resource theory as an analytical lens, with an assessment of the attributes of the resource and the user(s) to explore questions of governance and sustainability. In Hawai`i, spinner dolphins move predictably from offshore overnight feeding grounds into shallow bays for daytime rest, interacting frequently with humans using these bays for tourism and other social, recreational, and subsistence purposes. To reduce the current negative interactions with dolphins, managers are seeking to implement a command-and-control approach, namely time–area closures. Our analysis indicates that viewing the bay as a resource with tourism as one of many human demands, instead of specifically focusing on dolphins, reflects an ecosystem-based approach and acknowledges complex management demands. We found that while unrealistic to expect community-based conservation to spontaneously emerge here, cultivating some of Ostrom's attributes among stakeholders might lead to a more productive set of institutional arrangements that would benefit the dolphin population, with the methodology used potentially leading to a global management model.

Seasonality of strandings and bycatch of harbour porpoises in the Sea of Azov: the effects of fisheries, weather conditions, and life history

AbstractIn this study, we analyse seasonal aspects of harbour porpoise strandings in the Sea of Azov and discuss factors affecting the stranding rate. Data on 633 strandings were obtained from monitoring of a 35-km long area of the south coast of the Sea of Azov in 1999–2013. A distinct peak of strandings fell in July and August: it depended on the bycatch peak and calving season. Stranding rates depended neither on weather conditions nor on the seasonal fishing activities (including IUU fisheries). Moreover, stranding peaks in the neighbouring Black Sea were also tied to the calving season rather than to the fishing activities. We suggest that the seasonal mortality patterns are indirectly determined by nutritional stress: in Atlantic, winter-stranding oceanic populations and summer-stranding inner-sea populations occur that also possibly differ in the seasonal dynamics of body mass, weaning time or duration of mother–calf association, and dentine structure. In a typical summer-stranding population, summer is the season of nutritional stress, parturition, independent foraging of yearlings and lactation of nursing females, which leads to the risky foraging behaviour near gillnets. Another possible factor of increased bycatch is the seasonal habitat preference, corresponding to the gillnet preferences. Therefore, stranding and bycatch seasonality of porpoises can largely be explained by the aspects of their life history and foraging behaviour rather than by weather conditions and fisheries. This supports the time–area closure strategy as an adequate conservation measure, which would consider minimizing the conflict of interest with fisheries.

Towards defining good practices for modeling time-varying selectivity

Changes in the observed size- or age-composition of commercial catch can occur for a variety of reasons including: market demand, availability, temporal changes in growth, time-area closures, regulations, or change in fishing practice, to name but a few. Two common approaches for dealing with time-varying selectivity in assessment models are the use of discrete time-blocks associated with an epoch in the history of the fishery, or the use of penalized random walk models for parametric or non-parametric selectivity curves. Time block periods, or penalty weights associated with time-varying selectivity parameters, are subjective and often developed on an ad hoc basis. A factorial simulation–estimation experiment, with discrete or continuous changes in selectivity, is conducted to determine the best practices for modeling time-varying selectivity in fisheries stock assessments. Both the statistical properties of the assessment model and the policy implications of choosing the wrong model are taken into consideration.

Impact of Costa Rican longline fishery on its bycatch of sharks, stingrays, bony fish and olive ridley turtles (Lepidochelys olivacea)

We used data collected by an observer program to assess the impact of the Costa Rican longline fishery on numbers, capture locations, seasonality and body sizes of silky sharks (Carcharhinus falciformis), pelagic thresher sharks (Alopias pelagicus), olive ridley turtles (Lepidochelys olivacea) and other bycatch species in the Central American Pacific. The longline fishery caught a large number of mahi-mahi (Coryphaena sp.) and silky sharks, but also caught a large number of olive ridley turtles and pelagic stingrays (Pteroplatytrygon violacea). We estimated that longline fisheries caught 699,600 olive ridleys, including 92,300 adult females, from 1999 to 2010. These captures were associated with a decline of nesting populations at nearby arribada beaches. There were statistically significant size decreases from 1999 to 2010 in mature olive ridley turtles and from 2003 to 2010 in silky sharks. Average fork length of silky sharks in 2010 was 97.3cm, which was far below observed fork length at maturity, 144cm. Pelagic thresher sharks were small and fluctuated in size over the study period. Capture of large numbers of juvenile blacktip sharks (Carcharhinus limbatus) indicated a nursery area near the Osa Peninsula. Geospatial analysis indicated shifts in mahi-mahi abundance on a temporal scale but fishing efforts did not shift with the shift in mahi-mahi abundance. Yellowfin tuna (Thunnus albacares), Indo-Pacific blue marlin (Makaira mazara) and Indo-Pacific sailfish (Istiophorus platypterus) catches varied seasonally and were most abundant out to sea and south of Panama. Marine protected areas and/or time area closures are needed to reduce the impact of the Costa Rican longline fishery on sea turtles and sharks.

Analysis of harbor porpoise gillnet bycatch, compliance, and enforcement trends in the US northwestern Atlantic, January 1999 to May 2010

In 1999 the US National Marine Fisheries Service (NMFS) implemented regulations to limit harbor porpoise Phocoena phocoena incidental bycatch in US waters of the northwestern Atlantic. This effort was called the Harbor Porpoise Take Reduction Plan (HPTRP) and included a mixture of time-area closures, pinger and other gear modification requirements, a pinger training program, and outreach and education efforts. This paper focuses on the plan from January 1999 to May 2010 and examines trends in bycatch patterns, compliance with the plan, enforcement of the plan requirements, and changes in the primary fisheries involved in harbor porpoise bycatch. Over the course of the plan harbor porpoise bycatch dropped in the first few years, increased to unacceptable levels during the middle years, and moderated in the later years of the plan. Changes in fishing effort and distribution of key fisheries played a large role in decreasing the bycatch in much of the Mid-Atlantic and also in increasing bycatch in Southern New England and off the coast of New Jersey. The pattern in compliance levels had an inverse relationship with bycatch levels, with better compliance and lower bycatch in early and late years, though compli- ance was generally poor even when at its best. Enforcement of HPTRP regulations was not well documented, but, from available compliance data, it appears that what enforcement did occur was not sufficient to improve compliance. Given poor compliance with pinger requirements, these requirements have not resulted in the expected reduction in bycatch.

Comparing bycatch mitigation strategies for vulnerable marine megafauna

Marine megafauna such as seabirds, marine mammals and sea turtles are subject to high mortality from incidental capture or bycatch in fisheries. Recent research suggests that fishing effort is increasing worldwide, highlighting the need to evaluate strategies intended to reduce marine megafauna bycatch. Here, we use three focal species (i.e. leatherback turtle Dermochelys coriacea, black-footed albatross Phoebastria nigripes and vaquita porpoise Phocoena sinus) as case studies to compare management outcomes of four bycatch mitigation measures: time–area closures, individual bycatch limits, gear modifications and buy-outs. Time–area closures were used for leatherbacks and vaquitas with limited effectiveness, although timing, size and enforcement influenced their efficacy. Individual bycatch limits were employed for leatherbacks in one fishery, sometimes simultaneously with gear modifications and closures. Gear modifications consistently reduced bycatch of leatherbacks and black-footed albatross and showed strong promise for vaquitas. True buy-outs were only used for vaquitas and were costly, most fishers were unwilling to be bought out, and it is unclear if they reduced bycatch. Our review suggests that gear modifications were the most widely used and generally most promising technique for these species, although management outcomes of each strategy depended largely on the species–fishery interaction, fishery characteristics and socioeconomic context. Based on lessons learned from our case studies, we outline when and where a particular approach may be most effective, provide recommendations for improving each strategy and highlight priorities for future research.

Spatial and temporal patterns of anadromous alosine bycatch in the US Atlantic herring fishery

River herring, which comprise two species of anadromous alosines (alewife, Alosa pseudoharengus, and blueback herring, Alosa aestivalis), are under consideration for listing under the US Endangered Species Act. River herring populations have not rebounded despite reductions in directed fishing on these species and improvements in their freshwater and estuarine habitats. We examined recent (2005–2009) spatial and temporal patterns of fishing effort in the US fishery for Atlantic herring, Clupea harengus, and river herring bycatch patterns in this fishery. During the year, Atlantic herring fishing activity shifts spatially and temporally from the Northern Mid-Atlantic Bight and Southern New England waters in January–February, to Southern New England waters in March–April, to the Gulf of Maine in May–June, expanding to the Gulf of Maine and Georges Bank in July–August and September–October, respectively, and then contracting to the Gulf of Maine and Southern New England waters in November–December. At-sea fisheries observer data indicate that river herring bycatches in the Atlantic herring fishery occur mostly during January–April and September–December, primarily in Southern New England and the Northern Mid-Atlantic Bight waters. We discuss possible management measure to reduce these bycatches. Similar size, shape, and schooling behaviors between river herring and other pelagic species—and the high volume nature of the Atlantic herring fishery—limit the potential efficacy of gear-based bycatch mitigation measures. Hence, approaches such as regulatory management measures (e.g., time–area closures and catch caps) and improved fleet communication strategies (e.g., “move-on” rules) may be more practical and effective in minimizing river herring bycatch in the Atlantic herring fishery.

Habitat suitability analysis and identification of potential fishing grounds for swordfish, Xiphias gladius, in the South Atlantic Ocean

Swordfish, Xiphias gladius, is a highly migratory species of important commercial value and widely distributed in three oceans. Recently, the South Atlantic swordfish captured as by-catch in longline fisheries targeting tunas has contributed greatly to the overall Atlantic swordfish's landing. In this study, we have developed a habitat suitability index (HSI) model to examine the relationships between their spatio-temporal distribution and environmental factors and to identify potential fishing grounds for the swordfish in the South Atlantic Ocean using the Taiwanese distant-water longline fishery data and remote-sensing oceanographic data for 1998–2007. All the environmental factors considered – sea surface temperature (SST), mixed layer depth (MLD), sea surface height anomaly (SSHA), chlorophyll-a concentration (CHA) and ocean bathymetry (BAH) – were highly significant with most of the catch-per-unit-effort (CPUE) variation explained by SST. The most optimum habitat (i.e. hotspot) was found in the areas with SSTs of 27–28°C, SSHAs of −0.05 to 0.05 m, CHAs of 0.1–0.2 mg m−3 and BAHs of −4000 to −4500 m. The arithmetic mean model with five environmental variables was found to be the most appropriate according to the information theory based on the evaluation of different empirical HSI models in combination with different environmental factors. The bimonthly geographic information system maps of the predicted HSI values were cross-validated by the observed CPUE, suggesting that the model can be used as a tool for reliable prediction of potential fishing grounds. Because the distribution and relative abundance of swordfish are sufficiently heterogeneous in space and time, the output of this study could provide a scientific basis for time–area closures based management of this species.

Effects of time-area closure on tropical tuna purse-seine fleet dynamics through some fishery indicators

Time-area closures have become a frequently used tool to control fishing effort and protect feeding and spawning areas. However, because time-area closure strata are mainly based on biological and ecological considerations, and do not accounts for fishermen’s behavior-at-sea, this type of regulation tool may not entirely achieve its objectives. With the aim of comparing the impact of two different time-area regulations: (1) a moratorium on Fish Aggregating Devices (FAD) sets (1997–2005) and (2) a no-take area for surface fleets (2005–2010) on the dynamics of the European (EU) tuna purse seine fleet operating in the eastern tropical Atlantic, several fishery indicators were evaluated through a Before-After, Control-Impact (BACI) approach. The results showed that prior to any regulation, the fleet used to be concentrated within the Gulf of Guinea area. During the first years of the moratorium on FAD (from November to January within a large region in the eastern Atlantic) there was a movement towards outside the protected area, increasing the total sets on FAD (restricted fishing activity). In general, this moratorium fulfilled its objectives; however, it was not respected during the last years of this regulation. The no-take time-area closure restricted all tuna catches for the surface fisheries but only in November and within a small area (i.e., the Picolo zone). As a result, there was an increase in activities on free schools outside the no-take area. Our findings suggest the use of some simple fishery indicators to understand fleet dynamics as a complement of ecological information before implementing new time area closures. Furthermore, since tunas are highly mobile species, anticipating the possible re-allocation of effort of purse seiners to adjacent areas in response to the spatial regulation is required to design different candidate time-area closures and to evaluate their effectiveness to protect juvenile tunas.

Modelling the impacts of environmental variation on the distribution of blue marlin, Makaira nigricans, in the Pacific Ocean

Abstract Su, N-J., Sun, C-L., Punt, A. E., Yeh, S-Z., and DiNardo, G. 2011. Modelling the impacts of environmental variation on the distribution of blue marlin, Makaira nigricans, in the Pacific Ocean. – ICES Journal of Marine Science, 68: 1072–1080. Blue marlin are distributed throughout tropical and temperate waters in the Pacific Ocean. The preference of this species for particular habitats may affect its distribution and vulnerability to being caught. The relationships between the spatial pattern of blue marlin abundance and oceanographic conditions, which may be influenced by climate change, were examined using generalized additive models fitted to catch and effort data from longline fisheries. Distributions of blue marlin density, based on combining the probability of presence and abundance given presence, indicate that there is annual variation in the distribution of blue marlin and that the population apparently moved east during the 1997–1998 El Niño. The interannual variability in blue marlin distribution appears to be associated with El Niño events and is related to shifts in sea surface temperature and the deepening of the thermocline. Models of catch and effort that include oceanographic variables could be used, given predictions from climate models, to explore future changes in distribution, which could then be used to provide management advice related to time-area closures.

The role of discounting and dynamics in determining the economic efficiency of time-area closures for managing fishery bycatch

Time-area closures are commonly used to manage fisheries bycatch and involve temporarily closing an area of the ocean to particular fishing gears. We examine conditions in which implementing a time-area closure would increase the economic value of fisheries, focusing on a case study application in the Gulf of Mexico. Pelagic longline fishermen catch the highly valued Atlantic bluefin tuna (Thunnus thynnus, Scombridae) on their Gulf of Mexico spawning grounds while fishing for Atlantic yellowfin tuna (Thunnus albacares). We analyze a multispecies, multifishery bioeconomic model that includes information on migratory patterns from electronic tagged bluefin tuna. We use dynamic optimization to identify management strategies that would maximize the net present value of tuna fisheries, allowing for discounting of future benefits and costs relative to the present. If past fishing mortality rates continue in Atlantic bluefin tuna fisheries, implementing a time-area closure in the Gulf of Mexico incurs economic costs. However, the net present value of the fisheries is increased by implementing a time-area closure as part of a broader commitment to rebuild the heavily depleted bluefin population, provided the discount rate and the costs of such a closure in forgone fishing opportunities are not too large. The increase in economic value offered by a time-area closure is small relative to the overall economic value of rebuilding itself and it may be economically optimal only to implement a closure once sufficient rebuilding has already taken place.

The economic efficiency of a time–area closure to protect spawning bluefin tuna

Summary 1. Spatial management measures, such as time–area closures, offer a widely advocated strategy for managing bycatch in fisheries and fisheries that impact particular life‐history stages, like spawning. The effectiveness of proposed management strategies can be evaluated across different policy dimensions of which we focus on one – maximising total profit. We examine whether a time–area closure presents an economically efficient means to manage bycatches of Atlantic bluefin tuna Thunnus thynnus on their spawning ground in the Gulf of Mexico by longline fishermen targeting yellowfin tuna T. albacares. 2. We combine a behavioural representation of bluefin migration with population dynamic models for the two species and an economic representation of relevant fisheries and solve for optimal, equilibrial management strategies. 3. The models predict the western Atlantic bluefin population is close to open access harvesting conditions, and that rebuilding the bluefin population would increase overall economic revenues from the fisheries by 460%, regardless of the specific actions taken in the Gulf. 4. Time–area closures in the Gulf are predicted to be economically costly if there is little scope for recovery of the bluefin stock. However, the models predict such closures would offer limited economic benefits if there were a broader commitment to rebuild the bluefin population. 5. Synthesis and applications. Technological advances and improvements in our understanding of the life history of these and other species make increasingly precise spatial effort control possible in many fisheries. The case study illustrates when such management measures would maximise fisheries profits while accounting for population dynamics and differences in mortality from different fisheries. However, the case study also highlights that the more elementary policy challenge of preventing overfishing has still often to be overcome.

Aspects of the fishery, maturation and net selectivity of the wedge sole (Dicologoglossa cuneata) off south-western Iberia: implications for fishery management

The wedge sole (Dicologoglossa cuneata, Moreau 1881) is a commercially important species for the artisanal fleet operating off the south-western Iberian Peninsula. During 2004 and 2005 a study was undertaken aiming to provide a scientific basis for management. Data collection included information on aspects of the fishery, spawning season, size at first maturity, tangle and gill-net selectivity. Seven nominal mesh sizes were used (40, 45 and 50 mm tangle nets and 40, 50, 60 and 70 mm gill-nets). Spawning lasts from December to June, with peaks in March and May. Length at first maturity for females was estimated at 18.5 cm. Catch rates decreased sharply with increasing mesh size, with tangle nets providing the highest yields. The log-normal selectivity model provided the best fit for specimens that were wedged. The higher catch-per-unit-effort of the smaller mesh sizes and the modal length of the fitted selectivity curve being below the size-at-maturity for wedge sole, suggests that the 50 mm nominal mesh size tangle net is the most appropriate for ensuring the fishery sustainability. Nevertheless, the minimum legal size should increase to at least 18 cm and a time–area closure should be implemented off the Guadiana River mouth.

Threatened fishes of the world: Epinephelus marginatus (Lowe, 1834) (Serranidae: Epinephelinae)

Common names: Dusky grouper, garoupa-verdadeira.Conservation status: This species is listed as endan-gered in the Red List of Threatened Species (IUCN)(Marino et al. 2003; Cornish and Harmelin-Vivien2004). In Brazil, this species was included in the“over-exploitedorthreatenedwithoverexploitation”listof marine resources(Ministerio do Meio Ambiente IN52004) and in Sao Paulo State (Sao Paulo 2008).Identification:DXI+14–16; P 17–19; A III + 8; LL62–73. The pelvic fins are shorter than the pectoral finsand do not reaching the level of the anus. Themaximum length is 120 cm, with maximum bodyweight of 60 kg (Rocha and Costa 1999). Distribution:This species occurs on both sides of the Atlantic Ocean,from the British Isles to South Africa and southwestIndian Ocean in Southern Mozambique and Madagas-car (Heemstra and Randall 1993). Habitat and ecology:E. marginatus is a coastal, demersal species, commonlyfound over irregular rocky bottoms from shallow waterto 50 m deep (Heemstra and Randall 1993). E.marginatus plays an important role in maintaining theecological balance of hard-bottom ecosystems, with thefeeding based on fish and crustaceans (Barreiros andSantos 1998). Reproduction: This species is a protog-ynous hermaphrodite, with reproductive aggregationsand a complex social structure (Zabala et al 1997;Andrade et al. 2003). It becomes sexually mature whenreaching 45 cm and 2 kg, and maturing females occurbetween 3 and 9 kg. The sex inversion happens whenthey reach 9 to 10 years and 90 cm of length (Brusle1985;Marinoetal2001). Threats: Overfishing.Conservation action: Since 2003, in Brazil a minimumsize of capture was established at 47 cm. Conservationrecommendation: Time-area closures and the develop-ment of technologies for sexual inversion and spermcryopreservation (Sanches 2007; Cabrita et al 2009)are

Reducing seabird bycatch in the Hawaii longline tuna fishery

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 5:309-323 (2008) - DOI: https://doi.org/10.3354/esr00133 Reducing seabird bycatch in the Hawaii longline tuna fishery Eric Gilman1,2,*, Donald Kobayashi3,4, Milani Chaloupka5 1IUCN Global Marine Programme, 2718 Napuaa Place, Honolulu, Hawaii 96822, USA 2Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK 3US NOAA Fisheries, Pacific Islands Fisheries Science Center, 2570 Dole Street, Honolulu, Hawaii 96822, USA 4Department of Environmental Sciences, University of Technology, Sydney, New South Wales 2007, Australia 5Ecological Modeling Services, PO Box 6150, University of Queensland, St. Lucia, Queensland 4067, Australia *Email: eric.gilman@iucn.org ABSTRACT: Mortality in longline fisheries represents a global threat to some species of pelagic seabirds. Regulations were adopted in 2001 to reduce seabird bycatch in the Hawaii longline tuna fishery. We used a Poisson generalized additive regression modeling approach to evaluate the change in seabird bycatch rates from the pre- to post-regulation period, and to evaluate the efficacy of alternative combinations of seabird bycatch reduction methods employed during the post-regulation period. Informative covariates of temporal and geo-referenced spatial effects of fishing effort and sampling variation commonly found with count data were included in the model to provide a better inference of the effect of employing required changes in fishing gear and methods. We found a significant 67% (95% CI: 62 to 72) reduction in the seabird bycatch rate following the introduction of regulations. Post-regulation, sets employing 4 different combinations of seabird avoidance methods all resulted in significant reductions to the pre-regulation seabird catch rate. Employing side-setting and 60 g weights was the only combination with no seabird captures during the post-regulation period. Using heavier branch line weights and treated bait (thawed and dyed blue) both significantly reduced seabird catch rates. Temporal and spatial distribution of fishing effort and the timing of initiating setting were also significant factors affecting seabird bycatch rates: time-area closures and restricting the timing of setting could further reduce seabird bycatch. A substantial proportion of seabird captures occurred south of the area where mitigation measures are required: moving the southern boundary farther south would further reduce seabird catches. KEY WORDS: Albatross · Bycatch · Fisheries · Longline · Mitigation · Seabird Full text in pdf format PreviousNextCite this article as: Gilman E, Kobayashi D, Chaloupka M (2008) Reducing seabird bycatch in the Hawaii longline tuna fishery. Endang Species Res 5:309-323. https://doi.org/10.3354/esr00133 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 5, No. 2-3. Online publication date: December 23, 2008 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2008 Inter-Research.

Using Acoustic Monitoring to Evaluate MPAs for Shark Nursery Areas: The Importance of Long-term Data

The presence and movements of a population of young blacktip sharks (Carcharhinus limbatus) was monitored via a series of acoustic hydrophones over a period of three years to examine their use of a coastal nursery area. Data from this project were used to investigate the efficacy of hypothetical marine protected areas for this population. Small and large reserve designs were used to determine which would provide better protection for this population. The small reserve provided consistent levels of protection across years with sharks receiving good protection early in the summer season, but with declining protection thereafter. The large reserve provided less consistent levels of protection across years, but provided protection for a greater portion of time than the small reserve. Excursions from the small reserve were high early in the season and declined as sharks used this region less through the later portion of the summer. Excursions from the large reserve did not show any consistent pattern, but were also high early in the season and decreased through time as sharks used less of the reserve area. These results, coupled with previously calculated mortality estimates, revealed that the large reserve provided better protection for young sharks during their most vulnerable period within the nursery. We suggest that time-area closures for nursery populations of highly mobile shark species may be of value. Results of this study also show that long-term data may be critical to effective reserve design and placement, and assessment of reserve efficacy.

Assessment of the effectiveness of scup bycatch-reduction regulations in the Loligo squid fishery

Discard reduction is a component of the statutory requirements of the Sustainable Fisheries Act. One species of concern is scup, Stenotomus chrysops, discarded in the Loligo pealei fishery. Initially, regulations were imposed restricting the fishery in time and space to avoid areas and times associated with high scup discarding. Modified gear was required in 2003 on any boat fishing in areas otherwise closed to the fishery to reduce scup discarding. The purpose of this study was to evaluate the success of the 2003 net regulations and the potential influence of time–area closures (GRAs) in achieving a reduction in scup discarding. The regulations are based on three expectations. (1) Reduction in discarding in the Loligo squid fishery will materially reduce total scup discarding. (2) Exclusion of Loligo squid fishing vessels from the GRAs will result in these vessels fishing in areas that inherently produce fewer scup discards without equivalently increasing discarding in other sensitive species. (3) The use of a square-mesh large-mesh section in the extension will reduce scup discarding to the extent that otherwise would be achieved if the boats fished outside the GRAs without the economic cost imposed by redeploying the fleet. Analysis of the NMFS-NEFSC observer database offers no support for the belief that Expectation 1 has been met. Squid catches were too low to sustain a directed fishery in the northern GRA during this study. Thus, had this area been open, limited scup discarding would have occurred. In this study, squid catches averaged 1025 kg tow −1 in the southern GRA. Thus, had the GRA been open, Loligo fishing would have taken place. Yet, in the 34 tows taken by two vessels, not a single scup was caught. Redeployment of the fleet clearly increased scup discarding in 2003. Thus, Expectation 2 was not met. Field tests demonstrated that the implemented net modification can produce reduced catches of mostly smaller-sized finfish without impairing squid catch, but the data also indicate that this result may not be routinely achieved. Thus, Expectation 3 was not completely met. Implementation of the 2003 net regulation was likely premature, in that the specification was not adequate to guarantee the desired results. The history of the scup discarding issue in the Loligo squid fishery demonstrates that discard reduction cannot be accomplished without adequate prior evaluation of the sources of discards, without the requisite and concomitant experimental evaluation of the results of regulatory reform, and without adequate commercial-scale testing of prospective reforms prior to implementation.

Passive acoustic tracking of echolocating harbor porpoise (Phocoena phocoena). I. Fisheries management requirements and biological basis

Harbor porpoises are incidentally taken in various sink gillnet fisheries nationally. Little is known about the mechanism of these entanglements. To protect these animals as required by the Marine Mammal Protection Act (MMPA), fishery managers use time area closures and/or permit the use of acoustic deterrent devices (pingers) to reduce bycatch. To understand how an entanglement occurs and how the pingers function, one must understand the underwater behavior of the animals. Studies of captive porpoises, and using mounted instrumentation on released animals, have shown some aspects of porpoise life history but may or may not reveal natural behavior. A research program was initiated to determine the feasibility of passively tracking wild harbor porpoise using their echolocation signals (clicks) and observing their underwater movements in three dimensions. Additionally, details of these movements during feeding, traveling, and social events may provide an insight into their behavior that makes them prone to entanglement. Preliminary results demonstrate that the underwater tracking of harbor porpoises can be accomplished using this technique and several aspects of the animal’s natural behavior and communication are presented. A next generation autonomous system, to be deployed near actively fishing sink gillnets being developed, is described. [Work supported by NMFS and the URI/NOAA CMER Program.]