Total Fishing Effort Research Articles

Let’s measure it: An approach of high-resolution estimates of bottom fixed net fishing effort at national level

Fisheries are one of the most important food sources for human consumption whilst being amongst the most impacting and extractive activities happening within the marine environment, which makes it imperative to properly manage this activity. To improve fisheries management, the precise quantification of fishing effort is of the outmost importance. Yet, present methods for effort estimation, especially at broad scales, are hampered by difficulties in data access and usually rely on coarse effort metrics or on costly data collection for quantifying fishing effort with higher resolution. In the present work, we propose an approach of high-resolution fishing effort estimates of net fishing, as length of nets operated by a given fleet, at the national level. It relies on sampling of effort, derived from classified and easy to access vessel tracking data – AIS, and fishery dependent data – logbook and landings data. The proposed methodology combines trip-based effort estimates, derived from AIS data, as a foundation to extrapolate the total fishing effort, through the number of fishing trips linked to official landings and logbook data. It is estimated that in the years from 2014 to 2020 an average of 180 200 km of static nets (gillnets and trammel nets), which corresponds to approximately 4.5 and 210 times the lengths of the equator and the Portuguese Atlantic coastline respectively, are used in Portuguese mainland waters each year, by a fleet of slightly more than 100 vessels. The presented methodology allows to quantify and study the variation of the nominal fishing effort, at country level, with a higher resolution than what is usually used and at very low cost. We argue that such methodologies need to be developed and explored in order to have better and more comprehensive estimates of fishing effort which will contribute and improve the sustainable management of fisheries and the marine environment.

ANALISIS HASIL TANGKAPAN IKAN TONGKOL YANG DIDARATKAN DI PELABUHAN PERIKANAN NUSANTARA AMBON

This research aims to analyze the catches of tuna landed at the Ambon Nusantara Fisheries Port. The research was conducted for two months, from January to February 2023, using descriptive methods. Primary data was collected through direct observation and interviews with fishermen and port officers, while secondary data was obtained from PPN Ambon. The results of this research show that the catch was landed by four fishing fleets, namely purse seines, gill nets, fish trawls and lines fishing. The total catch landed during the 2012-2021 period was 510,203 tons, which was dominated by Auxis thazard. Purse seines are the most dominant fishing gear used, contributing 52.1% of the total catch with a total fishing effort of 597 trips. The productivity of the fishing fleet fluctuates from year to year, the lowest productivity for Euthynnus affinis occurred in 2018 and the highest in 2013, while the lowest productivity forl Auxis thazard occurred in 2017 and the highest in 2018. Fluctuating and low productivity indicates the existence of potential for overfishing. This research suggests the need for further analysis regarding the potential and level of utilization of the two species of frigate tuna landed in PPN Ambon

Using lessons learned from a multidecadal intercept survey of Puerto Rico spear fishers to improve data collection in the U.S. Caribbean

AbstractObjectiveSpearfishing is a common activity used to harvest coastal marine species worldwide and can be a significant contributor to landings of ecologically and economically relevant species. As such, it is important to monitor spearfishing catch and effort. Spearfishing is commonly practiced throughout the Caribbean, yet characteristics of this gear's fishery remain understudied in the region. Thus, the objectives of this study were to provide a description of the Puerto Rico spearfishing fishery utilizing a long‐term MRIP APAIS data set, examine the data set quality of this survey, and provide suggestions to improve MRIP implementation in the U.S. Caribbean.MethodsWe described the Puerto Rico recreational spearfishing fishery using a multidecadal (2000–2015) Marine Recreational Information Program (MRIP) Access Point Angler Intercept Survey conducted along the coast of Puerto Rico and surrounding territories. Data issues were identified in the survey results, including possible errors in measurement and identification; therefore, we limited analyses to species composition, enumeration, and mean catch rates.ResultThere were 89 species identified, with snappers (family Lutjanidae) being the most encountered family. Other economically relevant finfish frequently reported were Hogfish Lachnolaimus maximus (n = 121), Queen Triggerfish Balistes vetula (n = 115), and Red Hind Epinephelus guttatus (n = 90). Multiple reef fishes were landed during their spawning season, while prohibited by seasonal closures. Further, spearfishing accounted for 25.8% of the total harvest throughout the study period.ConclusionOur results suggest that spearfishing could be a considerable contributor to finfish landings in Puerto Rico, warranting its continued and improved monitoring in the region. Further, modifications in the design of fisheries surveys are warranted. We suggest increasing the allocation of resources, training, data quality assurance and quality control, and funding for the MRIP to maximize the accuracy of data obtained and meet MRIP U.S. Caribbean priorities. Implementation of a recreational fishing license would assist by creating a registry to monitor total recreational fishing effort and by generating funds to supplement the MRIP. The use of electronic reporting can help mitigate discrepancies with species identification and size measurements and enhance overall recreational fisheries data collection.

Marine protected areas can benefit biodiversity even when bycatch species only partially overlap fisheries

Abstract Marine protected areas (MPAs) are increasingly relied upon to preserve biodiversity and ensure fisheries sustainability. Although recent analyses have shown that MPAs can provide overall biodiversity benefits even when they only redistribute fishing effort, these did not account for refuges outside of fishing grounds for non‐target species. It has been argued that such refuges could render MPAs obsolete where their chief benefit is to ensure species persistence. Here, we modelled the outcomes associated with placing MPAs within a seascape where non‐target species' ranges can extend beyond fishing grounds. In scenarios with no explicit fishing‐induced habitat damage, we found that MPAs provided a net biodiversity benefit so long as there was at least an approximately 60% overlap between fishing grounds and non‐target species' ranges. In scenarios with explicit fishing‐induced habitat damage for non‐target species, we found that MPAs instead benefitted biodiversity at all overlaps, but that this was reduced if target species' abundances also declined with damage. Additionally, we identified counterintuitive mechanisms by which MPAs could either help or harm the same species depending on their location by changing fishing effort distribution patterns. However, MPAs did always increase the total fishing effort required to reach a catch target. Policy implications: Our results showed that MPAs could still deliver biodiversity benefits in otherwise well‐regulated fisheries when species' ranges and fishing grounds did not fully overlap, and particularly when sensitive species and habitats were present. Well‐placed MPAs should thus be considered in such settings. However, MPAs were also less likely to be useful when range overlaps were low and always resulted in higher fishing effort to maintain the same catches.

Spatiotemporal fishing effort simulations and restriction scenarios in Thermaikos Gulf, Greece (northeastern Mediterranean Sea)

Spatiotemporal simulation modeling is used in the context of ecosystem-based fisheries management to investigate different management options, including the size and allocation of marine protected and fisheries restricted areas. Here, we used ecospace to assess the effectiveness of existing and potential future spatiotemporal fishing restrictions in the heavily exploited Thermaikos Gulf, Greece for the years 2000–2025 (calibration period 2000–2016; projection period 2017–2025). ecospace combines temporal biomass and commercial catch data with spatial habitat and other environmental data, as well as species ecological preferences, feeding, and dispersal rates to depict changes in trophic interactions, biomasses, and commercial catches in time and space. ecospace simulations supported the empirical data demonstrating that fisheries restricted areas are effective tools for rebuilding the biomass of exploited stocks, with their size and location playing a significant role in the way that different organisms respond to protection. Nevertheless, our results suggested that in order to achieve the highest benefits of protection, fisheries restricted areas would need to be accompanied by a parallel reduction in total fishing effort, rather than a redistribution of fishing activities. Such redistribution would just move the pressure on the boundaries of protected areas, causing a local increase of commercial catches owing to the beneficial spillover effects of protection. One of the tested spatiotemporal restriction scenarios (MPA 5) suggests certain additional management measures on top of the existing restrictions for all four fishing fleets operating in the area. This scenario predicted a considerable increase in the biomass of key commercial and vulnerable species groups, including hake, flatfishes, anglerfish, sharks, and rays and skates, by the end of the simulation period in 2025.

Recreational Fishing Effort and How Management Actions Can Affect It—Part 2: Literature and a Case Study.

Recreational fishing, crucially important to Florida’s economy and ecosystems, can be affected by management decisions. Decisions that change the allowable harvest or the type of access to certain fishing areas are often expected to have strong effects on fishing effort, but the outcome of these actions is not always obvious. To provide greater insight into what may happen to fishing effort after management decisions, we describe case studies from the North American fisheries literature, some Florida-specific. These illustrate that the same or similar management actions (e.g., a more restrictive harvest policy) can have opposite effects on total fishing effort depending on the specifics of the case. We use this information as well as additional fisheries theory to explore a specific case study—what might happen if special harvest or access regulations were applied to a popular but ecologically and environmentally sensitive habitat—the St. Martins Marsh Aquatic Preserve in Citrus County, Florida.

Limited conservation efficacy of large-scale marine protected areas for Pacific skipjack and bigeye tunas

Large-scale, no-take marine protected areas (MPAs) have been established in several locations in the Pacific and expansion of such areas to reach 30% of the ocean area is actively promoted in some quarters. Justification for the establishment of large oceanic MPAs often includes the conservation benefits that they would bring for tuna stocks, which are the subject of important commercial fisheries in the Pacific. The aim of this paper was to evaluate the conservation efficacy of an existing MPA, the Phoenix Islands Protected Area (PIPA) and a series of large hypothetical MPAs each constituting approximately 33% of the western and central Pacific Ocean, for two important and contrasting tuna species, skipjack and bigeye tuna. The evaluation was conducted by comparing control and counterfactual simulations in which the estimated population and fishery dynamics of the species were modelled using a high-resolution modelling framework known as SEAPODYM (Spatial Ecosystem And Population DYnamics Model). We found that stock-wide conservation benefits of the PIPA for these species, assuming that total fishing effort is maintained, to be weak to non-existent, and only modest increases in spawning biomass of both species occur within and in the near vicinity of the PIPA itself. For the larger 33% hypothetical MPAs, changes in stock-wide spawning biomass were estimated to be -0.1% to +5.8% for skipjack tuna and +4.8% to +12.0% for bigeye tuna. Conservation efficacy of MPAs for species such as tropical tunas is limited by their wide larval dispersal and high mobility of later life stages, which spatially dissipate the protective effects of MPAs. Also, the displacement of fishing effort from MPAs to areas remaining open can have negative consequences for stocks and fisheries performance in those areas. We conclude that large oceanic MPAs are not likely to be effective frontline management tools for tropical tunas and other species having similar life history characteristics.

Trends in Indian Ocean marine fisheries since 1950: synthesis of reconstructed catch and effort data

Context Contrary to other ocean basins, Indian Ocean catches have increased consistently since 1950, although reported data are known to be incomplete. Fish is a crucial food source in the Indian Ocean; however, ineffective management often empowers over-exploitation. Aims We synthesised and reviewed Indian Ocean reconstructed catch and effort data by fishing sector and fishing country at the ocean-basin scale. Methods We aggregated reported and reconstructed unreported catch and effort data for the Indian Ocean and derived catch-per-unit-effort (CPUE) time-series by sector. Key results Indian Ocean rim country catches dominated in the Indian Ocean. Small-scale catches in the Indian Ocean have grown continuously by over 300% from 1.9 × 106 tonnes (Mg) year−1 in 1950 to 6.5 × 106 tonnes year−1 by 2018. By contrast, total industrial catches from the Indian Ocean have reached a plateau at ~8.5 × 106 tonnes year−1 since the late 1990s, after having steadily risen from very low levels in the early 1960s. Unreported catches declined from 45 to 25% of total catches. Total fishing effort, driven by the industrial sector, has increased 30-fold since 1950 from 0.4 × 109 to 11 × 109 kW-days by 2010, whereas CPUE has declined 78%, with steeper declines in the small-scale (>80% since 1950) than in the industrial sector (65% from its 1981 peak). Conclusions The different sectoral patterns in the Indian Ocean compared with other ocean basins are likely to be due to the region’s high dependence on small-scale fisheries and the later onset but swift growth of industrial fishing. The declining CPUE suggests strong decreases in stock biomass caused by strongly increasing fishing effort, especially in the industrial sector. Implications Indian Ocean countries should prioritise lower-impact well-managed domestic small-scale fisheries to maximise long-term, sustainable nutrient supply for local livelihoods.

DISTRIBUSI SPASIAL DAN TEMPORAL IKAN TUNA (Thunnus sp) DI PERAIRAN BARAT SUMATERA BERBASIS SISTEM INFORMASI GEOGRAFIS

One tool that can be used to visualize and connect various types of spatial and temporal distribution is Geographic Information System. The purpose of this study is to analyze the pressure of longline fisheries, tuna catches and fishing effort and can model the spatial distribution and temporal (of tuna, during longline fishery activities in 2013. Experimental methods are used in determining the size pixels and kernel shape. The form of the kernel that displays the best results is quartic. The optimal radius produced from the equation 0.68n-0.2 is 0.25 degrees (27.78 km). The CPUE uses raster data on catch density (tail field) and fishing line density (field number of hooks). The calculation is done by multiplying the density of the raster catch (tail) by 1,000 then divided by the density of the raster fishing hooks. The results show that the range of CPUE values ranged from 0.833 - 416. The total area of the total fishing effort was 161,520 km2 with an ffort of catching of 57,502.017 per 1,000 hooks. The total number of CPUE top heatmap is 38,948.29 per 1,000 hooks in 38,080 km2, most are in the Mentawai Strait, other parts are also found in the south of Siberut Island, west of Enggano Island to the Indian Ocean. Seasonal patterns show that the East season is the season with the highest catching effort in the Mentawai Strait, the Siberut Strait to the southern part of Siberut Island and the Transition I season is the lowest catching effort.
 Keywords: Spatial and temporal distribution, tuna density, CPUE, heatmap, Indian Ocean

Estimating Bycatch From Non-representative Samples (II): A Case Study of Pair Trawlers and Common Dolphins in the Bay of Biscay

Marine megafauna plays an important functional role in marine ecosystems as top predators but are threatened by a wide range of anthropogenic activities. Bycatch, the incidental capture of non-targeted species in commercial and recreational fisheries, is of particular concern for small cetacean species, such as dolphins and porpoises. In the North-East Atlantic, common dolphin (Delphinus delphis, Linné 1758) bycatch has been increasing and associated with large numbers of animals stranding during winter on the French Atlantic seashore since at least 2017. However, uncertainties around the true magnitude of common dolphin bycatch and the fisheries involved have led to delays in the implementation of mitigation measures. Current data collection on dolphin bycatch in France is with non-dedicated observers deployed on vessels for the purpose of national fisheries sampling programmes. These data cannot be assumed representative of the whole fisheries' bycatch events. This feature makes it difficult to use classic ratio estimators since they require a truly randomised sample of the fishery by dedicated observers. We applied a newly developed approach, regularised multilevel regression with post-stratification, to estimate total bycatch from unrepresentative samples and total fishing effort. The latter is needed for post-stratification and the former is analysed in a Bayesian framework with multilevel regression to regularise and better predict bycatch risk. We estimated the number of bycaught dolphins for each week and 10 International Council for the Exploration of the Sea (ICES) divisions from 2004 to 2020 by estimating jointly bycatch risk, haul duration, and the number of hauls per days at sea (DaS). Bycatch risk in pair trawlers flying the French flag was the highest in winter 2017 and 2019 and was associated with the longest haul durations. ICES divisions 8.a and 8.b (shelf part of the Bay of Biscay) were estimated to have the highest common dolphin bycatch. Our results were consistent with independent estimates of common dolphin bycatch from strandings. Our method show cases how non-representative observer data can nevertheless be analysed to estimate fishing duration, bycatch risk and, ultimately, the number of bycaught dolphins. These weekly-estimates improve upon current knowledge of the nature of common dolphin bycatch and can be used to inform management and policy decisions at a finer spatio-temporal scale than has been possible to date. Our results suggest that limiting haul duration, especially in winter, could serve as an effective mitigation strategy.

Effects of time-area closures on the distribution of snow crab fishing effort with respect to entanglement threat to North Atlantic right whales

AbstractTime-area closures are increasingly used to mitigate cetacean entanglement by temporarily excluding fishing effort from areas where high densities of cetaceans and fishing overlap. The effort displaced by these closures can be redistributed to the areas that remain open, changing the distribution and density of fishing effort outside the closures. These patterns were evaluated for the southern Gulf of St. Lawrence snow crab fishery by comparing recent years (2015–2017) with 2018 when time-area closures were implemented to protect North Atlantic right whales. A predictive model framework was created to test how well we could predict the response of fishers to closures. Approximately 29% of the total fishing effort was displaced by the 2018 closures, increasing effort density outside the closures by 41%. Displaced fishing effort shifted farther from the closures than predicted, into areas which, prior to 2018, had low effort density, producing a higher threat of entanglement in these new areas. Fishing effort in 2018 remained as high as 2017, despite a lower quota and reduced trap limit. Consequently, the resulting effects of time-area closures on fishing patterns outside of the closures cannot be discounted if entanglement threat to whales is to be successfully mitigated.

Making sense of firms for ocean governance

Making sense of firms for ocean governance

In the Wrong Place at the Wrong Time: Identifying Spatiotemporal Co-occurrence of Bycaught Common Dolphins and Fisheries in the Bay of Biscay (NE Atlantic) From 2010 to 2019

The first Unusual Mortality Event (UME) related to fishing activity along the Atlantic coast recorded by the French Stranding Network was in 1989: 697 small delphinids, mostly common dolphins, washed ashore, most of them with evidence of having been bycaught. Since then, UMEs of common dolphins have been observed nearly every year in the Bay of Biscay; unprecedented records were broken every year since 2016. The low and unequally distributed observation efforts aboard fishing vessels in the Bay of Biscay, as well as the lack of data on foreign fisheries necessitated the use of complementary data (such as stranding data) to elucidate the involvement of fisheries in dolphin bycatch. The aim of this work was to identify positive spatial and temporal correlations between the likely origins of bycaught stranded common dolphins (estimated from a mechanistic drift model) and fishing effort statistics inferred from Vessel Monitoring System (VMS) data on vessels >12 m long. Fisheries whose effort correlated positively with dolphin mortality areas after 2016 included French midwater trawlers, French Danish seiners, French gillnetters, French trammel netters, Spanish bottom trawlers, and Spanish gillnetters. For the French fleet only, logbook declarations, sales, and surveys carried out by Ifremer were integrated into fishing effort data. Six fleets were active in common dolphin bycatch areas at least twice between 2016 and 2019: gillnetters fishing hake, trammel netters fishing anglerfish, bottom pair trawlers fishing hake, midwater pair trawlers fishing sea bass and hake, and Danish seiners fishing whiting. Except for changes in hake landings in some fisheries, there were no notable changes in total fishing effort practice (gear or target species) based on the data required by the ICES and Council of the European Union that could explain the large increase in stranded common dolphins recorded along the French Atlantic coast after 2016. Small scale or unrecorded changes could have modified interactions between common dolphins and fisheries, but could not be detected through mandatory data-calls. The recent increase in strandings of bycaught common dolphins could have been caused by changes in their distribution and/or ecology, or changes in fishery practices that were undetectable through available data.

Effect of bait type on the octopus fishery in Algarve, Southern Portugal

In Algarve, southern Portugal, a fishery regulation was established forbidding the use of live crab as bait for the octopus fishing. Such a regulation was not established under a scientific fundament. The objective of this work was to identify if using live crab as bait affects the octopus fishery. Time series (1989–2015) were analysed in order to calculate octopus catch rates (as Landing Per Unit Effort or LPUE) and revenues (as revenue per unit effort or RPUE) before and after the crab bait ban in 2009 and also by bait type (crab and fish) before ban. Overall, total annual fishing effort decreased as result of the decreasing number of boats and fishing days in the local and coastal fleets. After the ban both the LPUE and RPUE increased, with total landings showing no change through time but mean landings per boat increased. Between 1989 and 2009, the mean monthly fishing effort in the coastal fleet was higher when crab bait was used (3.88%) in comparison to using fish bait (0.3%). This result is superimposed by the large inter annual variability between the local and coastal fleets (39.11%). In consequence, no substantial evidence was found indicating that crab bait produced high octopus catch rates, while fishing effort indicated that such high octopus catch rate and revenue increase was due to the decline of number of boats and fishing effort, that was decreasing significantly regardless of the bait type and fleet before to crab ban, and not to the bait type used during this period.

Definition of no‐fishing zones and fishing effort limits to reduce franciscana bycatch to sustainable levels in southern Brazil

AbstractFranciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western South Atlantic, with large regional variation. In 2012, the Brazilian Government‐regulated gillnet fisheries in south and southeast Brazil by reducing fishing effort and establishing no‐fishing zones. However, there is evidence that the magnitude of franciscana bycatch remains high and unsustainable. The aims of this study were to identify hotspot areas of franciscana bycatch associated with two main gillnet fisheries and to propose no‐fishing zones combined with limited total allowable fishing effort (i.e. total net length per season) in order to meet management objectives in southern Brazil. A hierarchical Bayesian model using integrated nested Laplace approximation (INLA) was employed based on 1427 reported settings from 1999 to 2003 and 2006 to 2009. Hotspot zones were detected and are proposed as no‐fishing zone during the white croaker Micropogonias furnieri and striped weakfish Cynoscion guatucupa gillnet fishing seasons. Their extents represent 6% (1466.8 km2) and 19% (4493.7 km2) of the fishing ground (23 204.1 km2) during croaker and weakfish fishing seasons respectively. The total allowable fishing effort estimated outside the no‐fishing zones were estimated at 541 km (95% credible interval (CrI) [339; 940]) during croaker and 688 km (CrI [312; 2,166]) during weakfish fishing seasons, one order of magnitude lower than the current total fishing effort. The drastic reduction of total fishing effort estimated in this study is largely due to weak protection measures since the gillnet fisheries became the major conservation concern for franciscana by the end of 1970s in southern Brazil. Although the implementation of the proposed exclusion zones and limiting fishing effort will strongly impact the status quo, they were based on the best scientific evidence and on a clearly defined management goal to reduce the risk of the franciscana population’s collapse in southern Brazil.

Modelling entanglement rates to estimate mortality of marine birds in British Columbia commercial salmon gillnet fisheries

Incidental mortality of marine birds in fisheries is an international conservation concern, including in Canada where globally significant populations of vulnerable diving species overlap with coastal gillnet fisheries. In British Columbia (BC), commercial salmon gillnet fishing effort was historically very high (>200,000 days fished annually in the early 1950's), and although this fishery has declined, over 6,400 days were fished annually in the 2006–2016 decade. Observations of seabird bycatch within the commercial fishery, however, are limited in both scope (comprising <2% of cumulative effort 2001–2016) and in time (being available only from 1995 onwards and only for a small number of areas). Using onboard fishery observer data from commercial, test and experimental fisheries (1995–2016), we developed two models to estimate the number of marine birds captured per set in sockeye (Oncorhynchus nerka) and chum (O. keta) salmon gillnet fisheries employing a Generalized Linear Mixed Modeling (GLMM) approach in a hierarchical Bayesian framework, with observer data post-stratified by fisheries management area and year. Using estimates of total commercial fishing effort (estimated number of sets, 2001–2016) we applied the models to extrapolate annual take for the main bird species (or groups) of interest. Multinomial probability estimates of species composition were calculated based upon a sample of 852 birds identified to species that were associated with sockeye or chum fisheries, enabling estimates (with CIs) of potential numbers of the mostly commonly observed species (common murres (Uria aalge), rhinoceros auklets (Cerorhinca monocerata), and marbled murrelets (Brachyramphus marmoratus)) entangled annually in commercial sockeye and chum salmon gillnet fisheries throughout BC. Conservative estimates of annual losses to entanglement were greatest for common murres (2,846, 95% CI: 2,628–3,047), followed by rhinoceros auklets (641, CI: 549–770) and marbled murrelets (228 CI: 156–346). Populations of all three of these alcids species are currently in decline in BC and entanglement mortality is a conservation concern. Gillnet mortality has been identified as a longstanding threat to marbled murrelet populations, which are recognized as Threatened in the Canada and the United States of America (USA). In addition, 622 (CI: 458–827) birds from 12 other species were estimated to be entangled annually. We conclude that cumulative mortality from incidental take in salmon gillnet fisheries is one of the largest sources of human-induced mortality for marine birds in BC waters, a conservation concern impacting both breeders and visiting migrants.

Estimating fishing effort across the landscape: A spatially extensive approach using models to integrate multiple data sources

Measuring fishing effort is one important element for effective management of recreational fisheries. Traditional intensive angler intercept survey methods collect many observations on a few water bodies per year to produce highly accurate estimates of fishing effort. However, scaling up this approach to understand landscapes with many systems, such as lake districts, is problematic. In these situations, spatially extensive sampling might be preferable to the traditional intensive sampling method. Here we validate a model-based approach that uses a smaller number of observations collected using multiple methods from many fishing sites to estimate total fishing effort across a fisheries landscape. We distributed on-site and aerial observations of fishing effort across 44 lakes in Vilas County, Wisconsin and then used generalized linear mixed models (GLMMs) to account for seasonal and daily trends as well as lake-specific differences in mean fishing effort. Estimates of total summer fishing effort predicted by GLMMs were on average within 11 % of those produced by traditional mean expansion. These estimates required less sampling effort per lake and can be produced for many more lakes per year. In spite of the higher uncertainty associated with model-based estimates from fewer observations, the improvements associated with the addition of only three aerial observations per lake highlighted the potential for improved precision with relatively few additional observations. Thus, the combination of GLMMs and extensive data collection from multiple sources could be used to estimate fishing effort in regions where intensive data collection for all fishing sites is infeasible, such as lake-rich landscapes. By using these methods of extensive data collection and model-based analysis, managers can produce frequently updated assessments of system states, which are important in developing proactive and dynamic management policies.

Shark discards in selective and mixed-species pelagic longline fisheries.

The conservation status of several pelagic shark species is considered vulnerable with declining populations, yet data on shark fishing mortality remain limited for large ocean regions. Pelagic sharks are increasingly retained by mixed-species fisheries, or are discarded and not reported by selective fisheries for tunas (Thunnus spp.) or swordfish (Xiphias gladius). We estimated the fishing mortality of sharks (landings plus discard mortalities) in a South African-flagged pelagic longline fishery with diverse targeting and discard behaviour. A hierarchical cluster analysis was used to stratify the fleet according to the relative proportions of tunas, swordfish, blue sharks (Prionace glauca) and shortfin mako sharks (Isurus oxyrinchus) landed by individual vessels between 2013 and 2015. A spatial analysis of logbook data indicated that subfleets operated in distinct fishing areas, with overlap. Approximately 5% of all commercial longlines set during 2015 were sampled by a fisheries-independent observer, and the species, discard ratios and physical condition at discard of 6 019 captured sharks were recorded. Blue sharks and shortfin makos dominated observed shark catches, which were comprised of nine species and two species groups. Some 47% of observed sharks were retained and 20% were discarded in good physical condition. Only 4% of shortfin makos were discarded, compared to 68% of blue sharks. Blue shark discard mortality rates were twice as high as published at-vessel mortality rates, suggesting that onboard handling, among other factors, contributed to discard mortalities. Extrapolation to total fishing effort indicated a near 10-fold increase in blue shark and shortfin mako fishing mortality compared to an earlier study (1998-2005). Escalating shortfin mako fishing mortality was attributed to increased targeting to supply higher market demand. Discarding of blue sharks by selective fishing for tunas and swordfish had a greater impact on their fishing mortality than retention by shark-directed fleets. Higher levels of observer sampling are required to increase confidence in discard ratio estimates.

A Baseline for the Blue Economy: Catch and Effort History in the Republic of Seychelles’ Domestic Fisheries

The adoption of sovereign blue bonds by the Republic of Seychelles, hereafter referred to as Seychelles, focuses on resource sustainability and illustrates options for island countries to use their ocean resources for years into the future. The fishing industry is one of the main pillars of Seychelles’ economy and is of crucial importance for domestic food- and employment-security. In order to promote long-term ecological sustainability and economic viability of domestic fisheries, accurate and long-term baseline information is required. Such baseline data were derived here with a reconstruction of the Seychelles’ domestic fisheries catches and fishing effort within its Exclusive Economic Zone (EEZ) from 1950–2017, coupled with resulting Catch Per Unit Effort data (CPUE). The total reconstructed domestic catch was approximately 1.5 times larger than the baseline as reported by the United Nations Food and Agriculture Organization (FAO) on behalf of Seychelles from 1950–2017 after adjustment for fully domestic catches within the EEZ. Domestic catches (i.e., excluding the large-scale industrial pelagic catches) increased by over 500% throughout the time period, growing from 1,900 t·year-1 in the 1950s to around 11,200 t· in 2017. The major targeted taxa were jacks (Carangidae), tuna-like fishes (Scombridae) and snappers (Lutjanidae). Total fishing effort in the form of fishing capacity grew from 21,500 kWdays in 1950 to over 3.4 million kWdays in 2017. The resultant artisanal CPUE displayed a declining trend over time, suggesting a potential decline in relative abundance of fish populations within the Seychelles EEZ or targeted fishing areas.

Catching industrial fishing incursions into inshore waters of Africa from space

AbstractSmall‐scale fisheries contribute substantially to the sustainability of coastal communities by providing livelihood and economic opportunities and ensuring food security. However, their geographic range of operation overlaps with that of industrial fisheries, increasing the resource competition, risk of vessel collision and inter‐sector conflicts, while jeopardizing the sustainability of fish stocks. When industrial vessels venture into waters that are reserved to artisanal fisheries, their operations become illegal. In Africa, the extent of such operations, beyond their legal implications, has resulted in severe economic, food security and maritime safety issues. In this paper, we use automatic identification system data derived from satellite technology to predict fishing operations and find that industrial fleets spend 3%–6% of their time fishing within inshore areas reserved for small‐scale fisheries between 2012 and 2016, of the total 4.2 million industrial fishing hours within the Exclusive Economic Zones of African countries. We assessed the total fishing effort by this form of illegal fishing operations at 166 million kWhours at least out of 4.9 billion kWhours in total. We discuss this dangerous form of illegal fishing, which often results in deadly collisions with small‐scale sector operators, increases competition and conflicts over fisheries access, threatens the sustainability of fish stocks, and calls for better governance, and protection.