Simulating drifting fish aggregating device trajectories to identify potential interactions with endangered sea turtles.

Purse-seine fishers using drifting fish aggregating devices (dFADs), mainly built with bamboo, plastic buoys, and plastic netting, to aggregate and catch tropical tuna, deploy 46,000-65,000 dFADs per year in the Pacific Ocean. Some of the major concerns associated with this widespread fishing device are potential entanglement of sea turtles and other marine fauna in dFAD netting; marine debris and pollution; and potential ecological damage via stranding on coral reefs, beaches, and other essential habitats for marine fauna. To assess and quantify the potential connectivity (number of dFADs deployed in an area and arriving in another area) between dFAD deployment areas and important oceanic or coastal habitat of critically endangered leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles in the Pacific Ocean, we conducted passive-drift Lagrangian experiments with simulated dFAD drift profiles and compared them with known important sea turtle areas. Up to 60% of dFADs from equatorial areas were arriving in essential sea turtle habitats. Connectivity was less when only areas where dFADs are currently deployed were used. Our simulations identified potential regions of dFAD interactions with migration and feeding habitats of the east Pacific leatherback turtle in the tropical southeastern Pacific Ocean; coastal habitats of leatherback and hawksbill in the western Pacific (e.g., archipelagic zones of Indonesia, Papua New Guinea, and Solomon Islands); and foraging habitat of leatherback in a large equatorial area south of Hawaii. Additional research is needed to estimate entanglements of sea turtles with dFADs at sea and to quantify the likely changes in connectivity and distribution of dFADs under new management measures, such as use of alternative nonentangling dFAD designs that biodegrade, or changes in deployment strategies, such as shifting locations.

Simulación de las trayectorias de dispositivos de concentración de peces a la deriva para identificar las interacciones potenciales con las tortugas marinas en peligro de extinción Resumen Los pescadores que usan redes de cerco con dispositivos de concentración de peces a la deriva (dFADs), hechos principalmente con bambú, boyas de plástico y redes de plástico, para concentrar y capturar atún, instalan entre 46,000 y 65,000 dFADs al año en el Océano Pacífico. Algunas de las problemáticas principales asociadas con este dispositivo de pesca de uso extenso son el enredamiento potencial de tortugas marinas y otras especies marinas en las redes de los dFADs; los desechos marinos y la contaminación; y el potencial daño ecológico por el varamiento en los arrecifes de coral, playas y otros hábitats esenciales para la fauna marina. Realizamos experimentos lagrangianos de deriva pasiva con la simulación de perfiles de deriva de los dFADs y los comparamos con áreas conocidas de importancia para las tortugas marinas. Esto fue con el objetivo de evaluar y cuantificar la conectividad potencial (número de dFADs instalados en un área que llegan a otra área) entre las áreas de instalación de dFADs y los hábitats oceánicos o costeros importantes para la tortuga laúd (Dermochelys coriacea) y la tortuga de carey (Eretmochelys imbricata), ambas en peligro crítico de extinción, en el Océano Pacífico. Hasta el 60% de los dFADs de las áreas ecuatoriales llegaron a los hábitats esenciales para las tortugas marinas. La conectividad fue menor sólo cuando se usaron áreas en donde actualmente hay dFADs instalados. Nuestras simulaciones identificaron regiones potenciales de interacción entre los dFADs y los hábitats de migración y alimentación de la tortuga laúd en el sureste tropical del Océano Pacífico; los hábitats costeros de ambas especies en el Pacífico occidental (p. ej.: zonas de archipiélagos en Indonesia, Papúa Nueva Guinea y en las Islas Salomón); y en el hábitat de forrajeo de la tortuga laúd en una gran área ecuatorial al sur de Hawái. Se requiere de mayor investigación para estimar el enredamiento de las tortugas marinas con los dFADs en el mar y para cuantificar los cambios probables en la conectividad y la distribución de los dFADs bajo nuevas medidas de manejo, como el uso alternativo de diseños que eviten el enredamiento y sean biodegradables, o cambios en las estrategias de instalación, como la reubicación.

Spatial information extraction of fishing grounds for light purse seine vessels in the Northwest Pacific Ocean based on AIS data.

Ecological fishery management requires high-precision fishery information to support resource management and marine spatial planning. In this paper, the Automatic Identification System (AIS) was adopted to extract the spatial information on the fishing grounds of light purse seine vessels in the Northwest Pacific Ocean. The spatial distributions of fishing grounds mapped by the data mining, kernel density analysis and hotspot analysis methods were compared. The spatial similarity index was applied to determine the spatial consistency between the computed spatial information and fisheries resource information. Finally, the spatial information derived by the best method was used to investigate the characteristics of fishing activity. The results showed that: the speed of light purse seine vessels related to operations was lower than 1.6 knots. The spatial information extracted by the three methods was consistent with the catch data distribution, and the spatial similarity between the fishing effort and catch data was the highest. The spatial variation in fishing activity was similar to that in the chub mackerel migration route. AIS data could be used to provide high-resolution fishery information. Light purse seine fishing vessels typically operate and travel along the exclusive economic zone boundary, and increased attention must be given to fishing vessel operation supervision. A comprehensive supervision system can be employed to monitor the operations of fishing vessels more effectively. The results of this study can provide technical support for the management of fishing activities and conservation of marine resources in this region using AIS data.

Biological patterns of reproduction of the Brazilian sardine Sardinella brasiliensis in the purse seine fishery of Southwest Atlantic Ocean: A long-term assessment.

Recent estimates of the size at first maturity (L50) of Sardinella brasiliensis showed contradictory results with a decreasing in the fish stock biomass encompassed by increasing values of L50. The methodological approach used hereby allowed to separate sardines classified in the virginal maturity stage from those categorized in the recovery stage, and ready for one next spawning event. This study evaluated the hypothesis of the existence of separated stocks experiencing distinct environmental conditions and fishing pressures which may have altered L50 estimates using a robust dataset based on biological samples collected along the entire species distribution area in the southeast-south Brazilian coast [Rio de Janeiro (RJ), São Paulo (SP), Paraná (PR), Santa Catarina (SC) and Rio Grande do Sul (RS)] between 2000 and 2018. A reclassification of the gonadal maturity stages provided a more realistic estimate of L50. Combining biological, reproductive, fishing data and the mean temperature of the catch (MTC), the leave-one-out classification correctly re-assigned individuals with an overall accuracy of 85% [100% (RJ), 45% (SP), 99% (PR), 99% (SC) and 82% (RS)]. The connectivity between the local populations of S. brasiliensis off RJ (23°S) and the southern populations is limited, contrasting to spatial structured semi-discrete population-units found between SP and RS (24°S-30°S). The northern extreme population-unit (RJ, 22°S-23°S) showed an expressive reduction of L50, and a negative correlation was detected between the increasing MTC values and the abundance of early maturing individuals and recruits of the species. Stock specific L50 estimates seemed to act as indicators of long term environmental fluctuations.

Characterising injuries and pathologies of common dolphin Delphinus delphis mortalities in the South Australian Sardine Fishery.

Mortality of dolphins in fishing operations is often under-estimated, as shown by studies of beach-washed carcasses. Linking evidence obtained during necropsies with fishing method is fundamental to understanding the extent of mortality and the manner in which animals die. The South Australian Sardine Fishery (SASF) has operated a purse-seine industry since 1991. This study characterised injuries, pathological changes and life history of 49 dead dolphins collected from SASF during 2006-2019. Histology examination was conducted on 25 animals. Neonates, calves and juveniles accounted for 63% of the sample. Of mature females (n = 14), 11 were pregnant or lactating, with cryptic mortality estimated to be 20% of dolphins studied. Body condition was robust in 48 dolphins. Net marks were seen on 82%, mostly on the head, trunk and peduncle. Broken/missing teeth were noted in 63%. All dolphins had subdermal haemorrhage (moderate to severe in 96%), particularly around the head. Deep haemorrhage was common, including around occipital and flipper condyles, and organs. Copious fluid was present in the thoracic (pleural) and abdominal (ascites) cavities of half of the dolphins. Within the lungs, watery fluid and froth were observed in 100 and 39%, respectively. Recent bone fractures were documented in 43% of dolphins, mostly associated with haemorrhage. Severe blunt trauma appeared to be the primary cause of death, and 10 dolphins also had other significant pathologies. Visceral organ congestion and mild cardiomyopathy were observed. Stomachs contained prey remains in 75% of cases. The results of this study may help identify unreported purse-seine mortalities washed up in South Australia and elsewhere.

Flotas de pesca extranjeras en el Pacífico costarricense y su traslape con áreas protegidas oceánicas, el ordenamiento pesquero y el Domo Térmico / Foreign fishing fleets in the Costa Rican Pacific and their overlap with oceanic protected areas, the fishing zoning, and the Thermal Dome

Introduction: Until today, the fishing effort by foreign fleets in the Costa Rican Pacific has not been analyzed. Objective: To determine the spatial distribution of the fishing effort of those fleets, variables that shape that distribution, and if they interact with management figures and highly fragile ecosystems. Methods: Using fishing effort data from 2012 to 2020, obtained from Global Fishing Watch, an Index of Fishing Effort (IEP) was calculated to apply geospatial and multivariate statistics, as well as multiple regression models. A grid with 55 905 cells of 0.10 degrees was used to apply Hot Spot Analysis, and another grid with 24 176 cell-year-month analysis units of 0.25 degrees was used to apply a Linear Regression Model. Results: The data reveals the fishing activity of international fleets associated with four types of fishing gear, and a wide coverage of a high IEP by two fleets throughout the nine years analyzed. The IEP is primarily associated with location and varies by month and year. There is also relative evidence that its influenced by the concentration of oxygen and nitrates. Conclusions: International fleets come into direct conflict with officially defined zones for national fleets and disrespect protected oceanic areas and a declared non-fishing zone to protect marine resources in the Costa Rican Pacific. Their activities in the Dome may affect a national yellowfin tuna fishery.

Introducción: Hasta hoy, no ha sido analizado el esfuerzo pesquero por parte de flotas extranjeras en el Pacífico de Costa Rica. Objetivo: Determinar la distribución espacial del esfuerzo pesquero de esas flotas, variables que moldean esa distribución, y si las mismas interactúan con figuras de manejo y ecosistemas altamente frágiles. Métodos: A partir de datos de esfuerzo pesquero de 2012 a 2020, obtenidos de Global Fishing Watch, fue calculado un Índice de Esfuerzo Pesquero (IEP) sobre el cual fue aplicada estadística geoespacial y multivariada, así como modelos de regresión múltiple. Fue utilizada una cuadrícula con 55 905 celdas de 0.10 grados, para aplicar Análisis de Puntos Calientes, y otra cuadrícula con 24 176 unidades de análisis celdas-año-mes de 0.25 grados, para aplicar un Modelo de Regresión Lineal. Resultados: Los datos revelan la actividad pesquera de las flotas internacionales asociadas a cuatro tipos de artes de pesca, así como una amplia cobertura de alto IEP por parte de dos flotas a lo largo de los nueve años analizados. El IEP se asocia principalmente con la ubicación y varía según el mes y el año. También hay evidencia relativa de que está influenciado por la concentración de oxígeno y nitratos. Conclusiones: Las flotas internacionales entran en conflicto directo con zonas oficialmente delimitadas para las flotas nacionales e irrespetan las áreas oceánicas protegidas y una zona no pesquera declarada para proteger los recursos marinos en el Pacífico costarricense. Sus actividades en el Domo pueden afectar la pesquería de atún aleta amarilla.

Environmental aspects and management preferences: A case study of small pelagic fisheries in the Crucita parish of the Portoviejo canton.

The extractive context of artisanal fishing in Ecuador is very broad and diverse considering the different fishing equipment that is used to capture a very varied set of species. As part of this broad sector, there is a small pelagic fishery, which is in the Crucita parish of the Portoviejo canton and is a long-standing and economically very relevant resource for the community. The objective of this article is to analyze the environmental and management aspects of this fishery as aspects relevant to achieving sustainable exploitation. To this end, information was collected from the beneficiaries of the purse-seine fishing fleet with the use of a structured questionnaire. The results revealed that there is widespread ignorance of the environmental aspects that affect the conservation of ecosystems and marine bioresources. On the other hand, the fishermen are aware of a general need to implement management measures that guarantee the sustainability of their fishing. However, they consider that the current regulations are not adapted to the current local context. Finally, from the perspective of those involved, the implementation of minimum capture sizes as a management measure could guarantee the sustainable capture of the species.

Hatch date and early growth of juvenile Japanese jack mackerel Trachurus japonicus caught in the Uwa Sea.

Development and growth rate variations during early life are important for understanding the mechanisms of recruitment dynamics. We examined the larval growth rate and age at the onset of metamorphosis (dm ) of juvenile Japanese jack mackerel recruited to a population in the Uwa Sea, Japan. Otolith microstructure analyses revealed that the hatch date of juveniles ranged from February to April in 2011-2015, and that their dm were 25.5-30.5 days and mean growth rates at the larval stage (GL ) were 0.30-0.34 mm day-1 . Among dm and GL , dm showed significant negative correlations with juvenile abundance. Moreover, the hatch date did not coincide with the spawning period of this species in the Uwa Sea, and the hatch date and mean growth rate at the larval stage were comparable to those of Japanese jack mackerel juveniles sampled in the East China Sea (ECS). These findings suggest that most juvenile Japanese jack mackerel originated in other waters, including the ECS, and that larval stage duration influenced their recruitment abundance in the Uwa Sea.

Environmental performance of Cantabrian (Northern Spain) pelagic fisheries: Assessment of purse seine and minor art fleets under a life cycle approach.

The perpetuation of fishing activity from an environmentally, socially and economically sustainable approach is essential to guarantee not only the future of coastal populations, but also the supply of high-value seafood for society and the safeguarding of cultural heritage. This article aims to assess the environmental performance associated with fishing fleet operations in Cantabria (northern Spain) under a life cycle thinking from a holistic approach. Thus, the Life Cycle Assessment (LCA) methodology was applied under a 'cradle-to-port' approach, setting the functional unit as 1 kg of fresh fish landed. Inventory data on the main inputs and outputs were collected from a sample of 57 vessels covering for the first time the main techniques, purse seine and minor art fisheries. The results identified that the vessel use stage was the responsible of most of the impacts. In line with the literature, diesel consumption stood as the chief hotspot in six of the seven impact categories analysed. Purse seiners got a value of 0.25 kg of fuel per kg of fish landed, while the performance of the minor art fleet showed significantly lower consumption (0.07). Regarding impacts on climate change, this study found a quantity of 1.00 and 0.34 kg CO2 eq. per FU, for purse seine and minor arts, respectively. These figures were consistent with the expected results for pelagic fisheries. For the remaining indicators, purse seiners generally performed worse. The LCA methodology provided outcomes that allow the proposal of potential improvements and measures to foster the transition towards a more sustainable smart-fishing sector. Further research efforts should focus on the development and implementation of renewable energy and low-carbon vessel propulsion technologies.

NMR-based metabolic profiling and discrimination of wild tropical tunas by species, size category, geographic origin, and on-board storage condition.

Tunas are among the most traded and valued fish species, and good traceability of tuna products in the world market is needed to protect both consumers and tuna stocks. To that purpose, high-resolution proton nuclear magnetic resonance (1H NMR) spectroscopy combined with multivariate data analysis was used to investigate the molecular components of the aqueous extract of white and red muscles in three species of wild tropical tuna species, namely yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis) and bigeye tuna (T. obesus). Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) applied to the processed 1H NMR spectra showed significant separation according to the species and size category (i.e., small tunas < 80 cm fork length vs large tunas > 80 cm fork length), the storage conditions on-board the purse-seine vessels (i.e., brine- vs deep-freezing), and the geographical origin (i.e., where the tuna was caught: Mozambique Channel vs western-central Indian Ocean). The major groups of metabolites responsible for differentiation in PLS-DA score plots were the dipeptides (anserine, carnosine) and organic acids (lactate, creatine/phosphocreatine) in the white muscle, and the free amino acids, essential nutrients (choline and its derivatives, phosphatidylethanolamine), dipeptides and organic acids in the red muscle. Our results showed that NMR-based metabolomics is a powerful tool to efficiently discriminate specific profiles among wild tuna species, raw muscle tissues, fish storage conditions and tuna geographical origin.

Tunabio: biological traits of tropical tuna and bycatch species caught by purse seine fisheries in the Western Indian and Eastern Central Atlantic Oceans.

Background: Along with the development of the tropical tuna purse-seine fishery from the 1960s in the Atlantic Ocean and from the 1980s in the Indian Ocean, many projects and studies have been conducted to improve knowledge about the biology, migrations and dynamics of the stocks of target and non-target (i.e. bycatch) species taken in these fisheries. Since the 2000s, the European Union (EU) has been supporting Member States in the collection of biological data on species caught by their purse seine and pole and line fisheries, thus making it possible to have a long-term series of data. Biological data have never been saved by the different tuna commissions, unlike the catches by species and sizes by areas and periods. However, these data are essential to monitor the status of the fisheries and fuel the assessment models used by the tuna Regional Fisheries Management Organisations (tRFMOs) for the sustainable management and conservation of the fish stocks under their mandate. New information: We combined historical (1974-1999) and current (2003-2020) datasets on the biology of tropical tunas and bycatch fish caught by large-scale purse seiners in the Eastern Atlantic Ocean (EAO) and Western Indian Ocean (WIO). The resulting Tunabio database is presented in the present data paper and contains all available morphometric and biological data collected on more than 80,000 fish individuals.

Fuel consumption and air emissions in one of the world's largest commercial fisheries.

The little information available on fuel consumption and emissions by high seas tuna fisheries indicates that the global tuna fleet may have consumed about 2.5 Mt of fuel in 2009, resulting in the production of about 9 Mt of CO2-equivalent greenhouse gases (GHGs), i.e., about 4.5-5% of the global fishing fleet emissions. We developed a model of annual fuel consumption for the large-scale purse seiners operating in the western Indian Ocean as a function of fishing effort, strategy, and vessel characteristics based on an original and unique data set of more than 4300 bunkering operations that spanned the period 2013-2019. We used the model to estimate the total fuel consumption and associated GHG and SO2 emissions of the Indian Ocean purse seine fishery between 1981 and 2019. Our results showed that the energetic performance of this fishery was characterized by strong interannual variability over the last four decades. This resulted from a combination of variations in tuna abundance but also changes in catchability and fishing strategy. In recent years, the increased targeting of schools associated with fish aggregating devices in response to market incentives combined with the IOTC management measure implemented to rebuild the stock of yellowfin tuna has strongly modified the productivity and spatio-temporal patterns of purse seine fishing. This had effects on fuel consumption and air pollutant emissions. Over the period 2015 to 2019, the purse seine fishery, including its support vessel component, annually consumed about 160,000 t of fuel and emitted 590,000 t of CO2-eq GHG. Furthermore, our results showed that air pollutant emissions can be significantly reduced when limits in fuel composition are imposed. In 2015, SO2 air pollution exceeded 1500 t, but successive implementation of sulphur limits in the Indian Ocean purse seine fishery in 2016 and 2018 have almost eliminated this pollution. Our findings highlight the need for a routine monitoring of fuel consumption with standardized methods to better assess the determinants of fuel consumption in fisheries and the air pollutants they emit in the atmosphere.

Risks to large marine protected areas posed by drifting fish aggregation devices.

Mapping and predicting the potential risk of fishing activities to large marine protected areas (MPAs), where management capacity is low but fish biomass may be globally important, is vital to prioritizing enforcement and maximizing conservation benefits. Drifting fish aggregating devices (dFADs) are a highly effective fishing method employed in purse seine fisheries that attract and accumulate biomass fish, making fish easier to catch. However, dFADs are associated with several negative impacts, including high bycatch rates and lost or abandoned dFADs becoming beached on sensitive coastal areas (e.g., coral reefs). Using Lagrangian particle modeling, we determined the potential transit of dFADs in a large MPA around the Chagos Archipelago in the central Indian Ocean. We then quantified the risk of dFADs beaching on the archipelago's reefs and atolls and determined the potential for dFADs to pass through the MPA, accumulate biomass while within, and export it into areas where it can be legally fished (i.e., transit). Over one-third (37.51%) of dFADs posed a risk of either beaching or transiting the MPA for >14 days, 17.70% posed a risk of beaching or transiting the MPA for >30 days, and 13.11% posed a risk of beaching or transiting the MPA for >40 days. Modeled dFADs deployed on the east and west of the perimeter were more likely to beach and have long transiting times (i.e., posed the highest risk). The Great Chagos Bank, the largest atoll in the archipelago, was the most likely site to be affected by dFADs beaching. Overall, understanding the interactions between static MPAs and drifting fishing gears is vital to developing suitable management plans to support enforcement of MPA boundaries and the functioning and sustainability of their associated biomass.

Riesgos para las Grandes Áreas Marinas Protegidas Ocasionados por los Dispositivos Agregadores de Peces a la Deriva Resumen El mapeo y la predicción del riesgo potencial que las actividades de pesca representan para las grandes áreas marinas (AMP), en donde la capacidad de manejo es baja pero la biomasa de peces puede ser de importancia global, son vitales para priorizar la aplicación y maximizar los beneficios de conservación. Los dispositivos agregadores de peces a la deriva (DAPds) son un método de pesca altamente efectivo y empleado en las pesquerías de redes de cerco. Estos dispositivos atraen y acumulan biomasa de peces, facilitando así la captura de peces. Sin embargo, los DAPd están asociados con varios impactos negativos, incluyendo tasas altas de captura accesoria y DAPd perdidos o abandonados que terminan varados en áreas costeras sensibles (p. ej.: arrecifes de coral). Mediante el modelado de partículas langrangianas, determinamos el tránsito potencial de los DAPd en una AMP grande alrededor del Archipiélago Chagos en el centro del Océano Índico. Después cuantificamos el riesgo de varamiento de los DAPd en los arrecifes y atolones del arrecife y determinamos el potencial que tienen los DAPd de pasar por la AMP, acumular biomasa durante el trayecto y exportarla a áreas en las que es legal su pesca (es decir, transitar). Más de un tercio (37.51%) de los DAPd representaron un riesgo de varamiento o tránsito a través de la AMP durante >14 días y el 17.70% representó un riesgo de varamiento o tránsito a través de la AMP durante >40 días. Los DAPd modelados desplegados en el este y en el oeste del perímetro tuvieron mayor probabilidad de varamiento o de tener tiempos de tránsito largos (es decir, representaron el riesgo más alto). El Gran Banco de Chagos, el atolón más grande en el archipiélago, fue el sitio con mayor probabilidad de ser afectado por el varamiento de los DAPd. En general, el entendimiento de las interacciones entre las AMP estáticas y el equipo de pesca a la deriva es vital para el desarrollo de planes de manejo adecuados para respaldar el cumplimiento de los límites de las AMP y el funcionamiento y sostenibilidad de la biomasa asociada a ellas.

Minimum drift times infer trajectories of ghost nets found in the Maldives.

This study explores methods to estimate minimum drift times of ghost nets found in the Maldives with the aim of identifying a putative origin. We highlight that percentage cover of biofouling organisms and capitulum length of Lepas anatifera are two methods that provide these estimates. Eight ghost nets were collected in the Maldives and estimated drift times ranged between 7.5 and 101 days. Additionally, Lagrangian simulations identified drift trajectories of 326 historical ghost nets records. Purse seine fisheries (associated with Korea, Mauritius, the Philippines, Spain, France and Seychelles) and gill nets from Sri Lanka were identified as 'high risk' fisheries with regard to likley origins of ghost nets drifting into the Maldives. These fisheries are active in areas where dense particle clusters occured (drift trajectories between 30 and 120 days). Interestingly, ghost nets drifting less than 30 days however, remained inside the exclusive economic zone of the Maldivian archipelago highlighting potential illegal, unreported and unregulated fishing activity is occuring in this area. This study therefore points to the urgent need for gear loss reporting to be undertaken, especially by purse seine and gill net fisheries in order to ascertain the source of this major threat to marine life. This should also be coupled with an improvment in the data focused on spatial distribution of the abandoned, lost or discarded fishing gear originating from both large- and small-scale fisheries.

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The use of fish aggregation devices (FADs) can increase catchability of tuna purse seine for associated tuna schools. In the past decades, large scale deployments of FADs have drawn the international attention due to their negative effects on the marine environment. Finding a FAD design ecologically and economically compatible has therefore become a challenge for tuna purse seine fishe-ry. Nowadays, knowledge and comprehension of interaction between FADs and catch species are quite lacking as a result of limited experimental investigation. We interviewed the captain of Chinese tuna purse seiner based on questionnaire to summarize the status of FADs deployment strategy, structural design, capture and ecological characteristics, and the behavior characteristics of associa-ted schools from the perspective of fishermen's knowledge and experience. We also quantified the cognitive differences of the investigated issues based on the index of consistency (IoC). Our results showed that: 1) the average number of year-round FADs deployment was (102±37) per vessel, and the number of that being lost was (72±1). 2) empirical knowledge from fishing masters indicated that man-made FADs could attract more tuna than natural floating objects (e.g. logs). Submerged structure was the predominant mechanism for aggregating tunas around the FADs. Hanging attractors (e.g. palm leaves) would facilitate the aggregation of tunas. 3) Fishing masters' observations in practical operation revealed that the duration needed for tunas to be associated with a FAD was around 32 days, and fish aggregation would tend to stabilize in the following month. Entanglement of sea turtles and sharks by netting was incidental events. 4) Most fishing masters had identical opinion on "bio-fouling was helpful for FADs to attract tunas" (IoC=0.73) and "modifying FADs design to reduce the detectability by other vessels" (IoC=0.73), while the answers for "the effect of raft type on tuna attraction capability" (IoC=0.34) were quite different. 5) The results of questionnaire suggested that the current design of FADs used by Chinese tropical tuna purse seiner had high risks of detected by other vessels and increased vulnerability of non-target species to fishery. Moreover, our results provided valuable references that promote sustainable exploitation of purse seine in a way of reconciling profitability with ecological preservation.

Muscle biochemistry of a pelagic delphinid (Stenella longirostris longirostris): insight into fishery-induced separation of mothers and calves.

The length of time required for postnatal maturation of the locomotor muscle (longissimus dorsi) biochemistry [myoglobin (Mb) content and buffering capacity] in marine mammals typically varies with nursing duration, but it can be accelerated by species-specific behavioral demands, such as deep-diving and sub-ice transit. We examined how the swimming demands of a pelagic lifestyle influence postnatal maturation of Mb and buffering capacity in spinner dolphins (Stenella longirostris longirostris). Mb content of newborn (1.16±0.07 g Mb per 100 g wet muscle mass, n=6) and juvenile (2.77±0.22 g per 100 g, n=4) spinner dolphins were only 19% and 46% of adult levels (6.00±0.74 g per 100 g, n=6), respectively. At birth, buffering capacity was 52.70±4.48 slykes (n=6) and increased to 78.53±1.91 slykes (n=6) once a body length of 141 cm was achieved, representing 1.6- to 2.0-year-old dolphins. Based on the age of weaning (1.3-1.6 years post-partum), muscle maturation occurred just after weaning as described for coastal bottlenose dolphins (Tursiops truncatus). Thus, a pelagic lifestyle does not promote rapid maturation of muscle biochemistry. Rather, it promotes enhanced muscle biochemistry: newborn and adult spinner dolphins had four- and two-times greater Mb contents than newborn and adult bottlenose dolphins, respectively. Indeed, adult levels rivaled those of deep-diving cetaceans. Nonetheless, the relatively underdeveloped muscle biochemistry of calves likely contributes to documented mother-calf separations for spinner dolphins chased by the tuna purse-seine fishery.

Adaptive responses of tropical tuna purse-seiners under temporal regulations.

The failure to achieve fisheries management objectives has been broadly discussed in international meetings. Measuring the effects of fishery regulations is difficult due to the lack of detailed information. The yellowfin tuna fishery in the eastern Pacific Ocean offers an opportunity to evaluate the fishers' responses to temporal regulations. We used data from observers on-board Mexican purse-seine fleet, which is the main fleet fishing on dolphin-associated tuna schools. In 2002, the Inter-American Tropical Tuna Commission implemented a closed season to reduce fishing effort for this fishery. For the period 1992-2008, we analysed three fishery indicators using generalized estimating equations to evaluate the fishers' response to the closure. We found that purse-seiners decreased their time spent in port, increased their fishing sets, and maintained their proportion of successful fishing sets. Our results highlight the relevance of accounting for the fisher behaviour to understand fisheries dynamics when establishing management regulations.

Tamaño óptimo de muestra del programa de observadores a bordo de la flota dirigida a la explotación de la anchoveta peruana (Engraulis ringens) / Optimum sample size for a program of observers on board fishing vessels targetting Peruvian anchovy (Engraulis ringens)

El monitoreo de la pesquería de anchoveta en el Perú es de suma importancia para la sostenibilidad del ecosistema de Humboldt. El Programa de observadores a bordo Bitácoras de Pesca constituye una rica plataforma de recolección de datos de las embarcaciones durante sus viajes de pesca, y donde se recopila información acerca de las capturas en cada lance, distribuciones de tallas, descartes, captura incidental, captura por unidad de esfuerzo, entre otros. Para que los indicadores obtenidos a partir de esta información tengan robustez es preciso contar con un método de solidez estadística para el cálculo del número necesario de viajes a muestrear. Este trabajo presenta un método con estas características, para calcular el número óptimo de viajes de manera independiente para cada una de las variables y a diferentes escalas de tiempo. Se muestra que, dependiendo del objetivo y de la escala temporal, la cantidad óptima de viajes a muestrear varía. A partir de estos resultados, se proporcionan recomendaciones prácticas sobre el tamaño de muestra para el Programa Bitácoras de Pesca. También se discute la aplicabilidad de esta metodología para otros recursos pelágicos.

Monitoring the anchovy fishery is of great importance for assuring the sustainability of the Humboldt ecosystem. The on-board observers program constitutes a rich platform for data collection for monitoring, as it consists of the collection of data from vessels during their fishing trips, regarding catches, size distribution, discards, catch per unit of effort, among others. To get robust indicators from these data, it is necessary to use a solid statistical procedure for computing the number of fishing trips to sample. This work presents a method with those characteristics, for computing each indicator independently and at different time scales. We show that the optimum size varies depending on the objective (indicator) and the time scale. Based on these results, practical recommendations for fixing the sample size are given. We finally discuss the aplicability of this methodology for other pelagic resources.

Weight-length relationships and Fulton's condition factors of skipjack tuna (Katsuwonus pelamis) in the western and central Pacific Ocean.

This paper describes the weight-length relationships (WLRs) and Fulton's condition factors (K) of skipjack tuna (Katsuwonus pelamis) in purse seine fisheries from three cruises in the western and central Pacific Ocean (WCPO): August-September 2009 (AS09), November-December 2012 (ND12), and June-July 2013 (JJ13). The fork length and weight of a total of 1678 specimens were measured. The results showed that the fork length of more than 70% of specimens was below 60 cm (76% in AS09, 87% in ND12, and 73% in JJ13). The coefficient b in the combined sex group was 3.367, 3.300 and 3.234 in JJ13, AS09 and ND12, respectively. The b values of WLRs when fork length was >60 cm were significantly less than 3 (P = 0.062), but when fork length was <60 cm they were significantly greater than 3 (P = 0.028). The K value ranges of JJ13, AS09 and ND12 in different fork length groups were 1.3-1.84 (1.62 ± 0.18), 1.57-2.02 (1.86 ± 0.15), and 1.44-1.78 (0.65 ± 0.13), respectively. Moreover, K values in different fork length classes for each cruise had one turning point: 60-65 cm for JJ13; 60-65 cm for ND12; and 55-60 cm for AS09. The results of this study provide basic information on the WLRs and K values of skipjack tuna in different seasons and growth phases in the WCPO, which are useful for fishery biologists and fishery managers.

Predicting current and future global distributions of whale sharks.

The Vulnerable (IUCN) whale shark spans warm and temperate waters around the globe. However, their present-day and possible future global distribution has never been predicted. Using 30 years (1980-2010) of whale shark observations recorded by tuna purse-seiners fishing in the Atlantic, Indian and Pacific Oceans, we applied generalized linear mixed-effects models to test the hypothesis that similar environmental covariates predict whale shark occurrence in all major ocean basins. We derived global predictors from satellite images for chlorophyll a and sea surface temperature, and bathymetric charts for depth, bottom slope and distance to shore. We randomly generated pseudo-absences within the area covered by the fisheries, and included fishing effort as an offset to account for potential sampling bias. We predicted sea surface temperatures for 2070 using an ensemble of five global circulation models under a no climate-policy reference scenario, and used these to predict changes in distribution. The full model (excluding standard deviation of sea surface temperature) had the highest relative statistical support (wAICc  = 0.99) and explained ca. 60% of the deviance. Habitat suitability was mainly driven by spatial variation in bathymetry and sea surface temperature among oceans, although these effects differed slightly among oceans. Predicted changes in sea surface temperature resulted in a slight shift of suitable habitat towards the poles in both the Atlantic and Indian Oceans (ca. 5°N and 3-8°S, respectively) accompanied by an overall range contraction (2.5-7.4% and 1.1-6.3%, respectively). Predicted changes in the Pacific Ocean were small. Assuming that whale shark environmental requirements and human disturbances (i.e. no stabilization of greenhouse gas emissions) remain similar, we show that warming sea surface temperatures might promote a net retreat from current aggregation areas and an overall redistribution of the species.