Showing papers on "Fishing published in 2023"

A review of cetacean interactions with longline gear

Abstract: Fishery-cetacean interactions, including those with longline gear, give rise to economic, ecological and social concerns. This paper reviews problems resulting from cetacean-longline interactions, considers potential strategies to reduce interactions and identifies research priorities and approaches. Depredation by cetaceans (removal and damage of hooked fish and bait from fishing gear) and damage and loss of fishing gear create economic problems; however, the magnitude of this problem is poorly understood. There is also insufficient information to determine whether there are population-level effects resulting from injury and mortality of cetaceans (from incidental entanglement and hooking and from deliberate actions to discourage depredation). Fishery-cetacean interactions may also: change cetacean foraging behaviour and distribution; increase fishing effort to make up for fish taken from gear by cetaceans; and create errors in fish stock assessments that do not account for cetacean depredation. Negative public perceptions of longline fishing can result from news of incidental and deliberate injury and mortality of cetaceans associated with longlining. Information on how to reduce cetacean interactions with longline gear is also limited, as is the understanding of the mechanisms responsible for them. Strategies already employed in some fleets include refraining from setting or cutting sets short when problematic species of cetaceans are observed and fleet coordination of daily fishing times and positions. Many fishermen perceive depredation as an inevitable part of fishing. This paper discusses a number of other possible cetacean avoidance strategies that warrant consideration, including: (1) fleet communication to enable vessels to avoid temporally and spatially unpredictable and sporadic hotspots of aggregations of cetaceans; (2) underwater acoustic masking devices to conceal the sound of the vessel, gear, and setting and hauling activities; (3) quieter vessels to reduce cetaceans’ ability to target longline vessels; (4) encasement of caught fish to reduce cetacean access to or interest in the catch; (5) use of bait or gear with an unpleasant smell or taste to reduce the attractiveness of gear, bait and catch to cetaceans; (6) use of pre-recorded fishing vessel sounds played from stations throughout a fleet’s fishing grounds to distract cetaceans from actual fishing vessels; (7) use of acoustic devices to mask returning cetacean echolocation signals; and (8) use of tethered sonobuoys to track cetaceans and enable fleet avoidance. Vessels with relatively low cetacean interaction rates should be examined for design and operational differences from vessels with high interaction rates, possibly allowing identification of effective avoidance methods. There is a need for experimentation in individual longline fisheries over several seasons to assess fisheryspecific efficacy and commercial viability of cetacean avoidance strategies. This is necessary as different cetacean species likely respond differently to an avoidance method and cetaceans may habituate to an avoidance strategy, especially in fisheries interacting with resident cetaceans.

Interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in Asinara Island National Park (Sardinia): assessment of catch damage and economic loss

Abstract: In 1999, the Italian Central Institute for Applied Marine Research (ICRAM), in response to reports made by local fisheries, began a study into the interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in the Asinara Island National Park (Sardinia). Using onboard observers, fishing boat surveys were carried out to determine the frequency of interactions, variations in the catch of target species and damage to two different types of trammel net caused by dolphins. Interactions occurred primarily with trammel nets targetting striped red mullet (Mullus surmuletus; the less valuable peacock wrasse, Simphodus tinca, was also caught). Interactions also occurred with trammel nets set for lobster (Palinurus elephas), cuttlefish (Sepia spp.) and scorpionfish (Scorpaena spp.), but these were considered negligible. The target species, catch and damage inflicted on the catch was recorded, both in the presence and absence of dolphins, in an effort to ascertain associated damage and economic cost. Loss of catch was found to be significant only in the case of nets deployed during the red striped mullet fishing season. Although the level of interaction was high relative to the narrow red striped mullet fishery season, the overall economic impact on the fishing community was found to be modest. The presence and regulations of the national park area may provide an opportunity for investigating mitigation activities compatible with both cetacean conservation and the maintenance of the traditional fisheries.

Updated estimates of harbour porpoise (Phocoena phocoena) bycatch in the Danish North Sea bottom-set gillnet fishery

Abstract: The bycatch of harbour porpoise in the Danish North Sea bottom-set gillnet fisheries between 1987-2001 is estimated using two methods involving extrapolation of observer data. When observed entanglements are extrapolated to fleet level based on target species landings, the annual bycatch was estimated to be in the range of 2,867-7,566 harbour porpoise with a mean of 5,817. When observations are extrapolated based on fishing effort, estimates are in the range of 3,887-7,366 porpoises with a mean of 5,591. Both methods estimate a significant reduction in bycatch in the most recent years due to a decrease in both effort and landings. However, the reduction is less pronounced with the effort based method.

Management of gillnet bycatch of cetaceans in New Zealand

Abstract: Bycatch of dolphins in inshore gillnets first attracted scientific and management attention in New Zealand in the 1980s. During 1984-88, 50-150 dusky dolphins were killed each year at Kaikoura in gillnets set at the surface to catch bait for rock lobster. At the same time, annual catches of 20-100 Hector’s dolphins occurred in Canterbury waters in bottom-set commercial and recreational gillnets. These catches resulted in the banning of surface-set gillnetting at Kaikoura in 1989 and in the creation of the Banks Peninsula Marine Mammal Sanctuary in 1988 to protect Hector’s dolphin. An additional gillnet closure was established to protect North Island Hector’s dolphin in 2003. A key problem is that current information on catches in these and other areas is scant. One observer programme has been successfully implemented in a commercial gillnet fishery (Canterbury area, 1997/98 fishing season). Its estimate of Hector’s dolphin bycatch (17) is clearly unsustainable by the local population. Pingers have been voluntarily used in these fisheries, but there are no data establishing their effectiveness, and it has not been possible to ensure consistency of pinger use. There are no reliable estimates of numbers taken in recreational fisheries. Area closures are used to mitigate gillnet bycatch of Hector’s dolphin, however it appears that the Banks Peninsula Marine Mammal Sanctuary is not large enough to ensure the persistence of the Canterbury population. There is a bycatch limit in place for this population, although it is unenforced. We argue that management of this species via bycatch limits is not practical, however. Hector’s dolphin’s low abundance and separation into several distinct populations means that appropriate bycatch limits would be very small, and this necessitates very comprehensive observer coverage to be confident they are not exceeded. We propose that increasing the size of protected areas is the most reliable option for conservation.

Insights on the use of dolphins (boto, Inia geoffrensis and tucuxi, Sotalia fluviatilis) for bait in the piracatinga (Calophysus macropterus) fishery in the western Brazilian Amazon

Abstract: In the Amazon Basin, the use of the pink dolphin or boto (Inia geoffrensis) for bait in the piracatinga (Calophysus macropterus) fishery was first detected in the year 2000. Since then, this artisanal fishery has become more prevalent as it requires only a few hours of work per night and provides immediate cash earnings. It is thus an attractive addition to (or replacement for) traditional fishing. Previous reports have noted the use of botos as bait, but stated that the most common bait used are caimans (Melanosuchus niger, Caiman crocodilus). Estimates of the number of dolphins killed based on fish landings have been proposed and an apparent decrease in sighting/survival of an artificially-marked boto population was observed. Although stocks/population estimates, trends and actual numbers of hunted dolphins are unknown, the conservation impacts of this activity are of concern. Between October 2010 and November 2011, research was conducted within an area with serious conflicts between dolphins and fishermen as well as intense fishing for piracatinga, i.e. in the lower Japurá River, on the border with the Mamirauá and Amanã Sustainable Development Reserves, where both boto and tucuxi (Sotalia fluviatilis) are used for bait. One-hundred and fifty-seven monitoring surveys were carried out in eight key communities, confirming 114 piracatinga fishing events through direct monitoring and incognito surveys of fishing gear (gaiolas). Empirical evidence of the activity in gaiolas comprised pieces of bait, carcass remains, piracatinga provoked vomits and dolphin fished carcasses. Of those, 31.2% (n = 35) involved cetacean bait (91.4% I. geoffrensis, 8.58% S. fluviatilis), 68.7% (n = 77) caiman bait (96% M. niger, 4% C. crocodilus), and two fishing events used both types. These percentages may be higher/lower in other areas within and outside the Reserves. Given the increasing trend of the piracatinga fishery, the authors believe that precautionary measures for the conservation of Amazonian dolphins are urgently needed. Development of practical short-term solutions (e.g. offal-baited fish traps) and multispecies management together with law enforcement, incentives and educational programmes could allow the future transition of riverine communities from the piracatinga fishery to sustainable, higher income activities.

Characterising an interaction between coastal bottlenose dolphins (Tursiops truncatus) and the spot gillnet fishery in southeastern North Carolina, USA

Abstract: The aim of this study was to characterise interactions between coastal bottlenose dolphins (Tursiops truncatus Montagu, 1821), and the autumn gillnet fishery in southeastern North Carolina, USA that targets spot (Leiostomus xanthurus). Beach based (conducted from April 1997 - January 1998) and aerial surveys (conducted from July 1998 - May 1999) were used to estimate the abundance of dolphins and gillnets in nearshore waters. Commercial spot landings records from Brunswick County, North Carolina were used as an index of prey abundance. Stranded bottlenose dolphins were evaluated using protocols developed to describe diagnostic evidence of human-induced fisheries mortality. During both survey periods, dolphin numbers, gillnet numbers and spot landings all peaked in October-November. Simultaneously, an increase in dolphin strandings bearing evidence of entanglement in gillnets (cuts, lacerations, or wrapping marks on their appendages) was observed. Four stranded dolphins were determined to have been killed in gillnets, and one dolphin was removed alive from a gillnet in October 1997. Six stranded dolphins were killed in gillnets in October and November 1998. Thus, 20-24% of the annual allowable human-induced mortality for all USA Atlantic coastal bottlenose dolphins could be attributed to monofilament gillnets targeting spot in October and November in southeastern North Carolina. Both recreational and commercial fishermen target spot in the autumn using gillnets and dolphin mortality may be attributable to both aspects of the fishery. Results of this study are cause for alarm because interactions between dolphins and coastal gillnets may be occurring at much larger spatial and temporal scales along the USA Atlantic coast. Understanding the relationships between the biological and anthropogenic variables leading to these interactions can facilitate conservative, pro-active, management ensuring that human-induced mortality is not negatively impacting populations of marine mammals, such as Atlantic coastal bottlenose dolphins.

An evaluation of gray whale (Eschrichtius robustus) mortality incidental to fishing operations in British Columbia, Canada

Abstract: Gray whale (Eschrichtius robustus) mortality incidental to commercial fishing operations in British Columbia (BC), Canada was evaluated by two methods: a mailed questionnaire survey of all commercial fishing licence holders in the province; and a review of records of incidental catches, strandings and dead floating animals from published and unpublished sources. Of 5,375 surveys sent out, 848 were returned of which 729 could be used (15.8%). Forty-two incidents with gray whales were reported, including three mortalities. From sources other than the questionnaire for the period up to 1989, 41 records of stranded and dead floating gray whales were obtained, of which four were judged to have been killed incidentally in fishing operations. Twenty-six of these animals had not been examined closely, but extrapolation from the 15 detailed records suggests that 27% of the dead gray whales reported in BC die incidentally in fisheries. Collisions with fishing gear are estimated to occur approximately 20 times per year. Mortality occurs in salmon drift gillnet, salmon seine, longline and trap fisheries. There is also one record of an individual entangled and drowned in a herring net pen, as well as an individual entangled in a herring set gillnet. Estimates of annual mortality are approximately two individuals using data obtained from the questionnaire and 2.4 individuals using stranding data. Biases are present for both sampling methods, but the estimated mortality levels are small relative to population size. Subsequent records (n = 40) for the period 1990–95 were also examined for comparison.

Biology and conservation of the franciscana (Pontoporia blainvillei) in the north of Rio de Janeiro State, Brazil

Abstract: This paper describes the interactions of the franciscana (Pontoporia blainvillei) with fisheries in the north of Rio de Janeiro State (210 18’S-220 25’S) and presents new information on its biology. A total of 181 dolphins were caught in gillnet fisheries in northern Rio de Janeiro from 1986-1999. The annual catch per unit effort (CPUE) values varied from 0.2-1.8 dolphins per gillnet fishing effort. Incidental captures were recorded throughout the year, usually less than 10 n.miles from shore, in depths less than 30m and in surface-set gillnets. There was no difference in the proportion of sexes (1 male:1.1 females). Males ranged from 66-130.0cm and 0-5 years and females from 74-147.5cm and 0-9 years. The predicted asymptotic length (using the Gompertz model) was 121.9cm for males and 145.6cm for females. Calving occurs throughout the year, with no seasonal pattern. Females attain sexual maturity at 3 years and 130.0cm in length and males at 2 years and 115.0cm. Individuals up to the age of three years represented 74% of the dolphins captured. Franciscana preferentially feed on the teleosts Stellifer sp., Anchoa filifera, Pellona harroweri and Isopisthus parvipinnis, measuring up to 10cm of length, and on the cephalopods Loligo sanpaulensis and L. plei. No internal parasites were observed. The barnacle Xenobalanus globicipitis was recorded on only one individual. Sightings were recorded in all seasons and 90% of them were obtained up to 5 n.miles from shore, in waters up to 15m deep. Around 70% of groups sighted consisted of up to five dolphins. Estimates of the population size and continuous gillnet fleet monitoring are required to conserve franciscana in the northern limit of its distribution range. The differences in the somatic, reproductive and genetic patterns of franciscana represent important aspects that may be used as evidence to best define their stocks. These variations may reflect the reduction of gene flow between populations, the allocation of resources between growth and reproduction and/or the influence of environmental features, such as water temperature and food availability.

The influence of whalewatching on the behaviour of migrating gray whales (Eschrichtius robustus) in Todos Santos Bay and surrounding waters, Baja California, Mexico

Abstract: This study investigated the influence of whalewatching boats on the behaviour of gray whales on their migratory route in Todos Santos Bay, near the port of Ensenada, Baja California, Mexico. The objectives were: (1) to compare the swimming direction and velocity of whales in the presence and absence of whalewatching vessels, and when other boats were fishing, cruising or drifting; and (2) to contribute scientific data to the improvement of whalewatching regulations for Todos Santos Bay and surrounding waters. During the winters of 1998 and 1999, theodolite tracking was undertaken from a lighthouse tower located on northern Todos Santos Island. During both years, the migration corridor was about 2.5km wide at the Todos Santos Islands; this is relatively narrow compared to other shore stations along the northern coast (USA). Sightings were separated into northbound or southbound migration routes and the variability of whale swimming direction was analysed by circular statistics. During the southbound migration, whale swimming direction was not different in the presence or absence of whalewatching vessels and other boats. This variable, however, was statistically different during the northbound migration both with whalewatching vessels (p = 0.007) and with other boats (p = 0.02). Whale swimming velocity showed significant differences without boats and with whalewatching boats during both migrations (northbound, p = 0.04; southbound, p < 0.001). Analysis of velocity in the absence and presence of other boats did not yield significant differences for either of the migrations. In addition, a head-on approach by whalewatching boats changed the whales’ swimming direction (p = 0.05) and velocity (p = 0.015) significantly when compared with an approach towards the rear or flanks. Although Mexican whalewatching law is explicit concerning manoeuvres around whale groups, an additional suggestion is made here to prevent unintentional head-on approaches.

Distribution and encounter rates of the river dolphin (Inia geoffrensis boliviensis) in the central Bolivian Amazon

Abstract: The ecology and conservation status of river dolphins (Inia sp.) distributed in the lowland rivers of Bolivia are poorly understood and only recently have basic studies been conducted to investigate their population size, taxonomic status, distribution, behaviour, environmental threats and ecology in this region. This paper examines the distribution and encounter rates of the bufeo (Inia sp.) in the middle reach of the Bolivian Amazon and was conducted in the Mamoré River and four of its tributaries during the low water season. Methods were employed which can be replicated during future surveys of Bolivian river dolphins and the results can be compared with those from surveys of Inia throughout its range. Sixty-two hours were spent surveying for dolphins, with 68% of the effort in Mamoré River and 32% in its tributaries. The Inia encounter rates reported here (1.6-5.8 dolphins km21) are the highest recorded anywhere in its broad geographic range; and indicate the importance of continuing and expanding surveys in this area. The mean group size was greatest in the Tijamuchi River (3.3±2.96) and smallest in the Yacuma River (1.8±0.75) and the maximum group size was 14. The high bufeo encounter rates in the central Bolivian Amazon can be taken as a reflection of the general environmental status of the region; however, a growing human population, associated with an increase in boat traffic and fishing activity, poses a future threat to bufeos and their aquatic habitats.

Relative abundance of harbour porpoises (Phocoena phocoena) from acoustic and visual surveys of the Baltic Sea and adjacent waters during 2001 and 2002

Abstract: Boat-based acoustic and visual surveys for harbour porpoises (Phocoena phocoena) were conducted during the summers of 2001 and 2002 in order to investigate their distribution and relative abundance in the Baltic Sea, and to compare the results with the adjacent Kiel and Mecklenburg Bights and the Little Belt. Harbour porpoises are subject to year-round bycatch in gillnets and other fishing gear in these waters. This is of particular concern in the Baltic Sea where a survey carried out in 1995 indicated that the population is low and current levels of anthropogenic mortality are believed to be unsustainable. Polish coastal waters were not included in the 1995 survey and it has been hypothesised that these unsurveyed waters may contain a significant uncounted part of the Baltic Sea population. Results show that the porpoise detection rate was two orders of magnitude lower in the Baltic Sea than in other waters surveyed. No evidence was found that Polish waters contain a significant, previously uncounted part of the Baltic Sea population. The results confirm the endangered status of the Baltic Sea population, and stress the urgency of preventing future anthropogenic mortalities that threaten the survival of the population.

An investigation of acoustic deterrent devices to reduce cetacean bycatch in an inshore set net fishery

Abstract: In Europe, problems with the use of pingers on larger fishing vessels have raised the question as to whether pingers would be practical on smaller vessels, which are a large proportion of the European static net fishing fleet. In this study, four netting vessels less than 10m long used AQUAmark pingers on part of their nets off the southwest coast of Britain over a 12 month period. Boat skippers recorded ease of use. Acoustic click detectors were deployed on test and control nets to assess the response of cetaceans to the pingers. No significant practical problems, apart from premature failure of pingers, were encountered. During the study, only one harbour porpoise was bycaught, in an unpingered net. In 650 days of acoustic data from pingered and non-pingered nets, matched by location, date and boat, there was a highly significant reduction in the number of porpoise clicks recorded at nets with pingers to 48% of the number predicted from the number recorded at control nets (range 35–51%). To assess habituation, single, modified pingers that were active for alternate seven hour periods were moored below a click detector at two sites, one of which has strong tides and high levels of associated ambient noise. This study showed a stronger pinger effect at the quiet site and a much reduced effect at the noisy site. There was evidence of a period of exclusion of porpoises following pinger use that could exceed seven hours, and no evidence of habituation. Results suggest that pingers are practical on small vessels, that they reduce harbour porpoise activity around nets and are therefore likely to reduce bycatch. Easier means of detecting pinger failure are needed. Pingers should be considered as a bycatch mitigation method in small vessel fisheries using bottom set nets.

A note on strandings and entanglements of humpback whales (Megaptera novaeangliae) in Ecuador

Abstract: Between June and September of each year, southeastern Pacific humpback whales, Megaptera novaeangliae, arrive on the Ecuadorian coast to reproduce. Between July 2001 and September 2002, seven new strandings of humpback whales were found at different places along the Ecuadorian coast. Three of them were related to incidental catches caused by fishing nets (gillnets) and one of them occurred outside of the humpback whales’ reproductive season. Using non-proportional and proportional 95% confidence interval calculations, it is estimated that the average frequency of strandings of humpback whales is 1.55 individuals per year (95% CI: 0.27,2.83; range: 1-4) since 1994, principally in the central and southern parts of the Ecuadorian coast, and the proportion of strandings due to bycatch is estimated at 0.286 (95% CI: 0.105,0.533). A preliminary mortality rate of 0.035(95% CI: 0.019,0.055), including both unknown and anthropogenic causes is estimated for this stock. 50% of the strandings took place in August and most were registered in 2001 (n=4). Six humpback whales with fishing nets embedded in their pectoral fins and tails were also observed in the marine area of the Machalilla National Park and the island of La Plata July-September. 67% of these entanglements occurred in July, and in one case a mother, accompanied by her calf, was observed with cables and a net on her head. These incidental catches are possibly related to the strandings occurring at the same time along the Ecuadorian shoreline. The fishery device most frequently linked to bycatch is the surface gillnet. Technological changes in fishing gear are vital for the conservation of marine mammals. It is imperative that the Ecuadorian coast be divided into zones and certain areas be delimited for the conservation of humpback whales through agreements with local users of the marine areas.

Southern right whale (Eubalaena australis) mortalities and human interactions in Australia, 1950-2006

Abstract: A total of 44 records of southern right whale mortalities and non-fatal anthropogenic interactions have been documented in Australia by museums, wildlife agencies and researchers since 1950. Sixteen of the events involved whales that apparently survived. Events were recorded in all months except January and 65% occurred in the period July to October. Mortalities were more numerous in the western half of the continent where southern right whales are more frequently observed. Events were classified according to their outcome and nature: carcasses (with no evidence of human interaction) n=25, fatal entanglements n=1, non-fatal entanglements n=12, fatal vessel collisions n=2, non-fatal vessel collisions n=3, non-fatal shooting n=1. No live strandings were recorded. The number of both mortalities and non-fatal anthropogenic incidents has increased 4-fold since the mid 1970s. More calves than ‘non-calf’ whales were present in the carcass category, whereas the opposite was the case for events involving human interaction. Lines, nets and buoys used in fishing crustaceans (rock-lobster, crab) were associated with several entanglements (n=5). A longline entanglement of a 14m female resulted in a chronic injury, debilitation and death. As a proportion of the total records for each region, there were fewer vessel collisions of right whales in Australia (11%) than in South Africa (16%) or the North Atlantic (35%).

Recent harbour porpoise bycatch in gillnet fisheries in Newfoundland and Labrador, Canada

Abstract: Despite reduced fishing effort in many North Atlantic fisheries following collapse of fish stocks, concerns remain about levels of direct mortality of harbour porpoise (Phocoena phocoena), primarily through incidental catches in fishing gear. Although harbour porpoise incidental catch is known to occur in several fisheries along the coast of Newfoundland and Labrador, Canada, there are no reliable quantitative estimates for the last decade when the commercial fisheries have undergone major changes in effort and target species. Based on incidental catch rates derived using different reporting methods, with net-days as measures of effort and fishing trips as sampling units, the potential number of incidental catches of harbour porpoises in several gillnet fisheries in Newfoundland waters was estimated for the years 2001, 2002 and 2003. Confidence intervals were calculated using re-sampling techniques. Incidental catches of small cetaceans were estimated to be 862 in 2001, 1,428 in 2002 and 2,228 in 2003 in Newfoundland gillnet fisheries; virtually all cetaceans reported were harbour porpoises. Annual estimates of incidental catch of small cetaceans varied greatly between fisheries and areas. Confidence intervals were large due to variation in reported incidental catch rates among individual fishers and geographic areas. Most small cetaceans were reported in the nearshore cod fishery, although there were also numerous reports of catches in nearshore fisheries for lumpfish, herring and Greenland halibut. Incidental catch of small cetaceans was also identified in offshore fisheries for monkfish, white hake and Greenland halibut. Most incidental catch events occurred during the third quarter of the year (July-September) along the south coast, although catches of harbour porpoises were also reported during the second and fourth quarters. Several strategies could be implemented to better monitor small cetacean incidental catch in Newfoundland and Labrador waters. However, harbour porpoise population estimates are required before it can be determined if this fisheries-related mortality occurring in Newfoundland is sustainable.

A note on the use of dolphins as bait in the artisanal fisheries off Bahía Solano, Chocó, Colombia

Abstract: Dolphin hunting for fishing bait in Bahía Solano, Chocó, Colombia, was evaluated during eight months, between July 2005 and April 2006. Interviews were conducted with 122 fishermen (18.2% of the registered fishermen in the zone), who cover at most 890km2 when fishing (approximately 2.3% of the Pacific Territorial Sea of Colombia), and data obtained from landings at a fishing company. Only fishermen using longlines (37.3%) confirmed using dolphins as bait. It was not possible to obtain additional information about date, specific location or dolphin species, but the most probable captured species were common bottlenose dolphin and pantropical spotted dolphin. Nine dolphins were killed during the study period (1.1 dolphins/month) and extrapolating these numbers to all fishermen using longlines in the region (250), 24 dolphins might have been taken during the study period (3 dolphins/month). Fish species caught using dolphin bait include Pacific bearded brotula, groupers and smooth-hound.

Distribution and Demography of the Alligator Snapping Turtle (Macrochelys temminckii) in Texas: A 20-Year Perspective

Abstract: Abstract - Texas contains the southwestern range edge of Macrochelys temminckii (Alligator Snapping Turtle), but there is relatively little published information on this species within the state. To document its range and assess temporal changes in its distribution and demography, we sampled 23 sites from 1999 to 2001. We then resurveyed 22 of these sites and sampled 29 additional sites in 2020–2021. Detection outcomes were consistent between 18 of the 22 resurveyed sites. Sex ratios and body-size distributions were similar across surveys. Catch per unit effort (CPUE) was lower in areas with trotlines, corroborating known interactions between turtles and fishing gear. Patterns in CPUE indicate Gulf of Mexico-draining watersheds are important systems for the species, while CPUE was lower in Mississippi-draining watersheds.

Getting off the ladder: Disentangling water quality indices to enhance the valuation of divergent ecosystem services

Abstract: Significance Benefit–cost analyses and ecosystem service assessments provide critical information that can guide society toward wiser stewardship of resources. When actions change multiple ecosystem services, representing the changes via single summaries or indices can mask underlying trade-offs between services. For some water quality scenarios, we find that combining ecosystem service metrics together into one index can yield lower benefit estimates, potentially changing relative costs and benefits. Consequently, even for very small changes in water quality, benefit estimates can differ substantially from benefits measured by decomposing the index and separately valuing the disparate ecosystem services.

Tracking elusive and shifting identities of the global fishing fleet

Abstract: Illegal, unreported, and unregulated (IUU) fishing costs billions of dollars per year and is enabled by vessels obfuscating their identity. Here, we combine identities of ~35,000 vessels with a decade of GPS data to provide a global assessment of fishing compliance, reflagging patterns, and fishing by foreign-owned vessels. About 17% of high seas fishing is by potentially unauthorized or internationally unregulated vessels, with hot spots of this activity in the west Indian and the southwest Atlantic Oceans. In addition, reflagging, a tactic often used to obscure oversight, occurs in just a few ports primarily by fleets with high foreign ownership. Fishing by foreign-owned vessels is concentrated in parts of high seas and certain national waters, often flying flags of convenience. These findings can address the global scope of potential IUU fishing and enable authorities to improve oversight.

A note on improving the mechanism of pinger attachment for the Danish North Sea gillnet fishery

Abstract: This paper describes development of a better mechanism for the attachment of pingers to fishing gear, aimed particularly at the Danish bottom-set gillnet fishery. In a cooperative effort involving gillnet fishermen, the fishermen’s organisations and researchers, modifications to the physical shape of a pinger and its attachment to the gear were developed, taking into consideration the acoustic functioning of the pinger, battery life, robustness to operational rigours, weight, volume, buoyancy, environmental effects, cost and handling. The suggested attachment (THOR-1) has a number of important advantages in this fishery compared to the more common head rope attachment. THOR1 was tested for ease of handling on board a gillnet vessel and found to perform very well, with minimal interference with normal fishing operations. The main disadvantage of THOR-1 is the need for an effective range of around 200m.

Mysticete whale abundance and observations of prey associations on the central Bering Sea shelf

Abstract: Visual surveys for cetaceans were conducted along transect lines in the central Bering Sea in association with a groundfish stock assessment survey from 5 July to 5 August 1999. There were 125 sightings of single or groups of mysticete whales during 6,043km of survey effort. Fin whales were most common (60% of all sightings), with distribution clustered along the outer continental shelf break near the 200m isobath. In addition, there were 27 sightings of minke whales and 17 sightings of humpback whales. Minke whales were primarily found along the upper slope in water 100-200m deep, while humpbacks clustered along the eastern Aleutian Islands and near the USA/Russian Convention Line southwest of St. Lawrence Island. Abundance estimates for fin, humpback and minke whales were: 4,951 (95% CI = 2,833-8,653); 1,175 (95% CI = 197-7,009) and 936 (95% CI = 473-1,852), respectively. These three species were the only ones for which sufficient on-effort sightings were available to estimate abundance. Sei whales, a gray whale and a pair of northern right whales were also seen. Although right whales have been seen in this area before, some behavioural details are provided here because observations of these whales remain rare.

Population dynamics of Arctica islandica off Long Island (USA): an analysis of sex-based demographics and regional comparisons

Abstract: The boreal bivalve Arctica islandica is an important fishery in the United States (US), yet very little is known about the resiliency of this species to fishing activity due to limited understanding of localized population demographics. Demographics including age frequency, recruitment patterns, mortality rates, and sexual dimorphism were evaluated for a population sampled off Long Island (LI, 40.09658°N 73.01057°W) and compared with samples from Georges Bank (GB, 40.72767°N, 67.79850°W) collected in 2015 and 2017, where GB was described in a previous study. This study supports evidence that this species is sexually dimorphic. Earlier assumptions of prolonged lapses in recruitment were not substantiated for either the GB or LI populations; yearly cohorts were observed for the past century, and both populations presented recruitment pulses in approximately 8-y periods. Estimated ages from this study are older than previously reported for the US Mid-Atlantic with the oldest animal represented by a 310-year-old male collected from LI. Simulated total mortality was higher at GB than LI, and higher for GB females than GB males, with simulated mean longevity estimates greater at LI than GB. The population sex ratio at GB was 1:1.1 (female:male), whereas the LI ratio was 1:1.4 and relatively deficient in large females. Recruitment into the populations occurs routinely with substantial hiatuses being rare and substantive year classes occurring at least decadally with lesser, but contributing, recruitment in most years in between. Routine recruitment may insulate this species from risks posed by overfishing to an extent not typical for other long-lived species.

Agreement on Fisheries Subsidies

Abstract: At the 12th Ministerial Conference in June 2022, Members of the World Trade Organization (WTO) reached a historic Agreement on Fisheries Subsidies that aims to contribute to the United Nations Sustainable Development Goals. This article provides the necessary background to the Agreement, tracing briefly the history to the negotiations. After a general overview of the Agreement, three key provisions of the Agreement are examined, namely, the prohibition of subsidies to (1) illegal, unreported and unregulated fishing, (2) the fishing of overexploited stocks, and (3) fisheries on the high seas outside the competence of regional fisheries management organisations. The provisions of the Agreement on special and differential treatment in favour of developing and least developed countries, as well as notable procedural and institutional features, are also considered. The remaining issues still to be addressed at the WTO are highlighted in the conclusion.