Seabird Bycatch Research Articles

Consensus management in Antarctica's high seas – Past success and current challenges

The high seas surrounding Antarctica have a vast and diverse marine environment. Following its establishment in 1982, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has managed the ecosystems of the high seas of the Southern Ocean. CCAMLR pioneered the ecosystem approach to resource management, took action on the problem of sea bird by-catch, and has established measures to combat illegal unreported and unregulated (IUU) fishing. CCAMLR is seen as an example of best practice in managing marine resources in international waters. At the same time, CCAMLR's challenges arise in the balance between ‘fishing’ and ‘conservation’ interests; for example in the current debates over climate change and marine protected areas in the Southern Ocean. In each of these examples, CCAMLR's consensus-based decision-making process has been a central element in shaping outcomes. This paper considers CCAMLR's achievements in sustainable marine ecosystems and identifies emerging challenges.

Assessment of seabird bycatch in the US Atlantic pelagic longline fishery, with an extra exploration on modeling spatial variation

Assessment of seabird bycatch in the US Atlantic pelagic longline fishery, with an extra exploration on modeling spatial variation

Risk Factors for Seabird Bycatch in a Pelagic Longline Tuna Fishery.

Capture in global pelagic longline fisheries threatens the viability of some seabird populations. The Hawaii longline tuna fishery annually catches hundreds of seabirds, primarily Laysan (Phoebastria immutabilis) and black-footed (P. nigripes) albatrosses. Since seabird regulations were introduced in 2001, the seabird catch rate has declined 74%. However, over the past decade, seabird catch levels significantly increased due to significant increasing trends in both effort and nominal seabird catch rates. We modelled observer data using a spatio-temporal generalized additive mixed model with zero-inflated Poisson likelihood to determine the significance of the effect of various risk factors on the seabird catch rate. The seabird catch rate significantly increased as annual mean multivariate ENSO index values increased, suggesting that decreasing ocean productivity observed in recent years in the central north Pacific may have contributed to the increasing trend in nominal seabird catch rate. A significant increasing trend in number of albatrosses attending vessels, possibly linked to declining regional ocean productivity and increasing absolute abundance of black-footed albatrosses, may also have contributed to the increasing nominal seabird catch rate. Largest opportunities for reductions are through augmented efficacy of seabird bycatch mitigation north of 23° N where mitigation methods are required and during setting instead of during hauling. Both side vs. stern setting, and blue-dyed vs. untreated bait significantly reduced the seabird catch rate. Of two options for meeting regulatory requirements, side setting had a significantly lower seabird catch rate than blue-dyed bait. There was significant spatio-temporal and seasonal variation in the risk of seabird capture with highest catch rates in April and May and to the northwest of the main Hawaiian Islands.

Important foraging areas of seabirds from Anguilla, Caribbean: Implications for marine spatial planning

Marine spatial planning (MSP) has become an important tool to balance the needs of commercial, economical and recreational users of the marine environment with the protection of marine biodiversity. BirdLife International advocate the designation of marine Important Bird Areas (IBAs) as a key tool to improve the protection and sustainable management of the oceans, including the designation of Marine Protected Areas, which can feed into MSP processes. This study presents the results of three years of seabird tracking from the UK Overseas Territory of Anguilla, where marine resources are currently relatively unexploited and MSP is in its infancy. The core foraging areas of 1326 foraging trips from 238 individuals, representing five species (brown booby Sula leucogaster, masked booby Sula dactylatra, sooty tern Onychoprion fuscatus, magnificent frigatebird Fregata magnificens and red-billed tropicbird Phaethon aethereus) breeding on three of Anguilla's offshore cays were used to calculate the hotspot foraging areas for each study species. These high activity areas were then compared with fishing activity within Anguilla's Exclusive Economic zone and to proposed coastal developments. Two marine IBAs were identified within Anguilla's waters: the first to be defined, using seabird tracking data, in the Caribbean region. Whilst the level of fishing activity and associated seabird by-catch is hard to quantify, the core foraging areas of seabirds breeding in Anguilla were observed to overlap with areas known for high fishing activity. These findings highlight the need to work both nationally and across territorial boundaries to implement appropriate marine spatial planning.

Modeling spatially-varying ecological relationships using geographically weighted generalized linear model: A simulation study based on longline seabird bycatch

Geographically weighted regression (GWR) is a relatively new technique to explore spatially-varying relationships between biological and environmental processes. It allows parameters to vary over space and assumes data to follow a normal distribution. We extend GWR to a geographically weighted generalized linear model (GW-GLM) by incorporating statistical distributions other than the normal distribution (i.e., the binomial distribution). We demonstrate the application of GW-GLM with an empirical example, U.S. Atlantic pelagic longline seabird bycatch. Due to the high percentage of zero observations in the seabird bycatch data, we analyzed the positive catch rates (number of seabirds caught per 1000 hooks) and the probability of catching a seabird separately. Parameter estimates exhibited considerable spatial variation, especially for target catch rate when analyzing the positive catch data, and for intercept, water depth and water temperature when estimating the probability of catching seabirds. We compared model performance of GW-GLM with a global generalized linear model, a mixed effect model with a random areal effect, and a spatial expansion model that is an early technique to model spatially-varying ecological relationships by modeling each of the parameters as a function of location. The GW-GLM performed best. Simulations with hypothetical datasets having different percentages of zeros showed that, regardless of the zero percentage in the data, GW-GLM performed best on average. Applying a range of bandwidth indicated that the GW-GLM was more robust to an overestimated bandwidth than an underestimated bandwidth.

Influence of electric fishing lights on sink rates of baited hooks in Brazilian pelagic longline fisheries: implications for seabird bycatch

The incidental mortality of seabirds in longline fisheries is the major cause of the population declines threatening most albatross and large petrel species (LEWISON; CROWDER, 2003; ANDERSON et al., 2011). Currently there is a large and growing number of solutions for reducing seabird mortality on longlines. The combination of certain mitigation measures can greatly reduce seabird bycatch, although no single mitigation measure can reliably prevent seabird mortality. The combination of night setting, bird scaring lines and well-weighted branch lines are the best practice for the mitigation of seabird bycatch in pelagic longline fisheries (ACAP, 2014).The sink rate of baited hooks is arguably the major issue to be addressed to reduce seabird-longline interactions. Even when scaring lines are used, to make them effective the baited hooks must attain safe depths (i.e. deeper than the diving range of most petrel species) within the area protected by a scaring line. Many factors are known to affect the sink rate of baited hooks on pelagic longlines, such as the bait type (e.g. squid, mackerel, sardine, skipjack flash) and its state (e.g. dead or alive, frozen or thawed); the mainline tension during deployment; and line weight regimes (the use or not of leaded swivels, as well as their mass and distance from the hooks) (ANDERSON; MCARDLE, 2002; PETERSON et al., 2008, ROBERTSON et al., 2010; ROBERTSON et al., 2013).The best weighting regimes recommended are those that reach a depth of 10 m while under the protection of a scaring line with ~100 m aerial coverage (PETERSEN et al., 2008, MELVIN et al., 2009a). Experiments have indicated that ≥ 60 g placed no more than 3 m from the hooks is likely to achieve satisfactory sink rates under most operational conditions (MELVIN et al., 2009b; ROBERTSON et al., 2010; GIANUCA et al., 2011). Accordingly, among the best practices to reduce seabird mortality in pelagic longline fisheries recommended by the Agreement on the Conservation of Albatrosses and Petrels (ACAP, 2014) and the International Commission for the Conservation of Atlantic Tunas (ICCAT, 2011), is to use specific line-weighting regimes that ensure appropriate sink rates. The three recommended configurations are: weight greater than 45 g attached within 1 m of the hook or greater than 60 g attached within 3.5 m of the hook or greater than 98 g attached within 4 m of the hook. Positioning the weight farther than 4 m from the hook is not recommended.The use of chemical light sticks and more recently battery powered electric fishing lights (EFL), increases catch rates by attracting target species directly or by attracting their prey (BERKELEY et al., 1981; FREEMAN, 1989; ORTIZ; SCOTT, 2001; HAZIN et al., 2005). Despite the addition of this kind of device (usually ~2 m from the hooks) alters the surface/volume ratio of the terminal portion of the branch lines and potentially the sink rate of baited hooks, no investigation has yet been undertaken on this issue.EFL have recently been adopted by the southern Brazilian pelagic longline fleet, and their use and popularity are growing among fishermen and ship owners. Each EFL carries two AA batteries and, given its weight out of the water (~160 g), some fishermen argue that the use of this kind of device increases the sink rate of baited hooks, and using this untested premise as justification for not adopting the required line-weighting regimes.In the light of this scenario, the aim of the present

Life in the open ocean: seasonal migration and diel diving behaviour of Southern Hemisphere porbeagle sharks (Lamna nasus)

A wide range of pelagic predators survive in the open ocean, yet little is known about how they use that environment. Much of the current information on these species comes from studies in shelf waters, and it is not clear how representative the results are of their oceanic lifestyle. We used pop-up satellite tags to explore the horizontal and vertical use of the open ocean by porbeagle sharks (Lamna nasus) in the south-west Pacific Ocean and to identify possible mitigation measures to reduce their bycatch in tuna longline fisheries. Ten porbeagle sharks were tracked in waters around New Zealand for 72–300 days (median 221 days). Sharks made horizontal movements of hundreds to thousands of kilometres, with a maximum estimated track length of almost 10,000 km. Mature females made seasonal latitudinal migrations from ~46–48°S in summer to ~35–38°S during winter–spring, where they are hypothesised to give birth to pups. Porbeagle sharks exhibited diel vertical migration, diving deeper during the day than at night. Dives generally began at dawn and finished at dusk and lasted 11–15 h depending on day length. Porbeagles feed mainly on mesopelagic fish and squid and appear to forage in the vertically migrating deep scattering layer. All sharks dived to at least 600 m with a maximum recorded depth of 1024 m. During the day, most of their time was spent at depths of 200–600 m in the open ocean. Porbeagle shark bycatch could be substantially reduced by limiting longline fishing to daylight hours when they are too deep to be caught. However, longliners currently set mainly at night to avoid seabird bycatch, which would increase unless other mitigation measures were implemented to protect them. A review of factors affecting the bycatch of various species, and the impact of mitigation measures on catches of target species, is required to identify an appropriate suite of management measures.

Estimating mortality of black-browed albatross (Thalassarche melanophris, Temminck, 1828) and other seabirds in the Argentinean factory trawl fleet and the use of bird-scaring lines as a mitigation measure

Seabird bycatch represents one of the main threats to vulnerable seabird populations, particularly albatross and petrels, and requires urgent conservation management interventions at a global scale. We studied seabird mortality associated with demersal factory trawl vessels that target Argentine Hake Merluccius hubbsi along the Argentine Patagonian Shelf and tested the efficacy of bird-scaring lines as a seabird bycatch mitigation measure. From November 2008 to June 2010, dedicated seabird observers recorded three sources of seabird mortality: entanglements with the trawl net; collisions with the trawl cables (corpses hauled aboard); and collisions with trawl cables (birds observed killed or injured). During 141 days and 389 hauls, we recorded 17 seabird species associated with vessels, ten of which interacted with fishing gear. The most vulnerable species was the black-browed albatross (Thalassarche melanophris). From 41 recovered corpses, we identified black-browed albatross mortality rates of 0.013 and 0.093 birds/haul for net entanglement and cable collision (corpses hauled aboard), respectively. From counts of birds killed or injured by cable collisions, we estimate a black-browed albatross mortality rate of 0.237 birds/h. We use official fishing effort data to consider the potential scale of seabird mortality for the entire fleet and identify the main factors contributing to seabird mortality in this fishery. Bird-scaring lines eliminated seabird mortality caused by collisions with trawl cables and are recommended as a short- to medium-term measure to mitigate seabird mortality in this fishery.

Incidental catch of seabirds and sea turtles by Taiwanese longline fleets in the Pacific Ocean

To understand the sea turtle and seabird bycatch of Taiwanese tuna longline fleets for conservation purposes, this research analyzed the data collected by onboard observers between 2008 and 2013. In total, data from 149 trips and 24.3 million hooks were analyzed, including 50 albacore large-scale tuna longline vessel (LTLVs) trips, 72 bigeye LTLVs trips, and 27 small-scale tuna longline vessel (STLVs) trips. Seabird bycatch was mostly from the albacore LTLVs. The highest bycatch rate was 0.320 bird per thousand hooks in the southwest Pacific Ocean in the first quarter, followed by the same area in the second quarter (0.046 bird per thousand hooks) by the albacore LTLVs. For seabird bycatch species, 81.7% were albatrosses, including wandering albatross (Diomedea exulans), Laysan albatross (Phoebastria immutabilis), white-capped albatross (Thalassarche steadi), black-footed albatross (Phoebastria nigripes), and black-browed albatrosses (Diomedea melanophris); other seabird species included white-chinned petrel (Procellaria aequinoctialis), flesh-footed shearwater (Puffinus carneipes), frigate bird and booby. Regarding sea turtles, the bycatch rate peaked in the second quarter in the western tropical Pacific Ocean by STLVs (0.034 turtle per thousand hooks), followed by albacore LTLVs (0.028 turtle per thousand hooks) during the same time period in the same region. The major bycatch species included olive ridley (Lepidochelys olivacea), followed by green (Chelonia mydas), and leatherback (Dermochelys coriacea). Observer training for seabird species identification and detailed information collection for mitigation measures should be implemented to ensure better data quality. This will help implement mitigation measures in areas and fisheries where a large number of birds are taken as bycatch.

An integrated assessment model of seabird population dynamics: can individual heterogeneity in susceptibility to fishing explain abundance trends in Crozet wandering albatross?

SummarySeabirds have been incidentally caught in distant‐water longline fleets operating in the Southern Ocean since at least the 1970s, and breeding numbers for some populations have shown marked trends of decline and recovery concomitant with longline fishing effort within their distributions. However, lacking is an understanding of how forms of among‐individual heterogeneity may interact with fisheries bycatch and influence population dynamics.We develop a model that uses comprehensive data on the spatial and temporal distributions of fishing effort and seabird foraging to estimate temporal overlaps, fishery catchability and consequent bycatch. We apply a population model that is structured by age, sex, life stage and spatially to Crozet Island wandering albatross and explore how heterogeneity in susceptibility to capture may have influenced the population's demography over time.A model where some birds were assumed to be more susceptible to fisheries bycatch was able to successfully replicate the observed trend in breeding pairs. Considerably poorer fits were found without this assumption. Results suggested that the more susceptible birds may have been removed from the population by the 1990s.The model was also able to highlight areas, times and fleets prone to increased bycatch. Knowledge of these factors should assist fisheries and conservation management bodies to quantify and reduce seabird bycatch through spatial management and fleet‐specific mitigation efforts.Synthesis and application. Many seabirds show complex life histories that make them highly susceptible to additional incidental mortality from fishing vessels. By applying a population model that integrates key aspects of seabird and fishery dynamics, we were able to explain the observed trends in the breeding population of Crozet wandering albatross and identify key areas and fleets where further mitigation may be required. In addition, the potential removal of a category of birds that shows increased susceptibility to capture has important implications for the conservation management of this population and other iconic species incidentally caught by large‐scale commercial fisheries.

Assessing incidental bycatch of seabirds in Norwegian coastal commercial fisheries: Empirical and methodological lessons

With diminishing seabird populations and little knowledge on incidental bycatch in fisheries in the Northeast Atlantic, this study aimed to screen seabird bycatch in Norwegian coastal fisheries in 2009. The purpose was to 1) quantify magnitude of seabird bycatch rates and estimate total bycatch from the entire fleet by different estimators 2) evaluate data from an access point survey against monitoring data from a reference fleet as methods for collecting data on bycatch mortality of seabirds and 3) give advice on further bycatch studies. The study focused on three small-vessel fisheries (<15 m LOA) outside Northern Norway; the coastal cod (gillnet and manual longline) and lumpfish (gillnet) fisheries and the more offshore Greenland halibut longline fishery. We found no correlation between landed catch and bycatch and upscaling was made based on number of fishing trips. In these fisheries, northern fulmars Fulmarus glacialis outnumbered the other species and constituted almost half of the overall bycatch, totalling about 5500 (mostly on longlines) of the >11 000 birds estimated caught. The black guillemot Cepphus gryllealso stood out as a numerous victim, constituting almost two thirds of the >3000 birds estimated to have drowned in lumpfish gillnets. The two methods were both considered to hold merit and yielded approximately similar estimates of the bycatch in the coastal cod fisheries, however BPUE differs. Further studies are recommended especially on the lumpfish gillnet and Greenland halibut longline fisheries and on temporal and spatial variations in bycatch. More studies are also needed to model effects on seabirds at the population level.

Two devices for mitigating odontocete bycatch and depredation at the hook in tropical pelagic longline fisheries

AbstractOdontocete bycatch on and depredation from tropical pelagic longlines is globally widespread, having negative impacts on the economic viability of affected fisheries and on the conservation of affected odontocete populations. Reports by fishers that depredating odontocetes avoid gear tangles has underpinned the development of simulated structures to physically deter depredating odontocetes. This study assessed the efficacy of two such devices developed to mitigate odontocete depredation and associated bycatch. Of particular interest was their impact on (i) soak depth and (ii) sink rate using truncated trials, before determining their impact under full operational conditions on rates of (iii) catch of the five most economically important fish, and (iv) odontocete depredation and bycatch, on changes in (v) fish survival and size, and (vi) setting and hauling speed. The results indicated that the inclusion of devices on longlines had negligible impact on soak depth, thus were unlikely to impact on the suite of fish specifically targeted and caught. The sink rate was slowed, perhaps by drag, trapped air, or propeller wash, although the addition of weight might remedy this if the devices were to be used in areas where seabird bycatch could occur. Most importantly, trials conducted in Australian and in Fijian waters indicated that pooled fish catch rates (i.e. albacore, yellowfin, bigeye, mahi mahi, and wahoo) increased in the presence of the devices, possibly because more fish were attracted by them or because more depredators were deterred. Catch rates on control gear next to gear with devices attached were higher than more distant control gear, suggesting the influences of the devices may have extended to adjacent branchlines. The size of caught fish was mostly unaffected, although the survival of yellowfin and bigeye increased significantly in the presence of the devices. Hauling was slowed by the use of the devices and the need for an extra crewmember during setting and hauling, which could be cost prohibitive in some fisheries, especially if economic benefits from their use are not obvious. Despite the small sample size, odontocete bycatch only occurred on unprotected fishing gear and all individuals were released alive, although their fate was uncertain; there was evidence of injuries sustained from the event. The outcomes are positive and should motivate stakeholders to view such devices as a potentially effective tool for mitigating odontocete bycatch and depredation in this and similar longline fisheries. Future efforts should focus on improving operational integration and reducing implementation costs to encourage voluntary uptake and thus avoid non-compliance and the need for costly monitoring. The use of this technology could bring about marked improvements to the conservation situation for affected odontocete populations and to the economic situation for affected longline fisheries.

Characterization of seabird bycatch in eastern Canadian waters, 1998–2011, assessed from onboard fisheries observer data

Abstract Seabird bycatch in commercial fisheries has been a growing conservation concern over the past 25 years. Large‐scale fisheries employing gears known to incidentally catch seabirds operate off eastern Canada, however, regional bycatch information is limited. Using data collected from 1998–2011 by observers onboard Canadian domestic and foreign vessels, fishery sectors and target fisheries taking seabirds were identified, as were the seabirds most frequently taken. In addition, maps of seabird bycatch rates were used to identify localized areas where catch rates were high. Seabird bycatch was widespread. Despite generally low observer coverage, &gt; 5000 bird deaths were recorded; most observed mortalities occurred in gillnet and longline sectors during summer and autumn. While the overall magnitude of seabird bycatch has likely decreased substantially since closure of the Atlantic cod Gadus morhua and Atlantic salmon Salmo salar gillnet fisheries in 1992, localized areas with high bycatch rates persist. For example, in Baffin Bay and Davis Strait, bycatch rates of northern fulmars Fulmarus glacialis were high in gillnet and longline fisheries targeting Greenland halibut Reinhardtius hippoglossoides near breeding colonies. In offshore areas of the Grand Bank, catch rates of migrant shearwaters (Puffinus and Calonectris spp.) were high in deep‐set gillnet fisheries for Greenland halibut and monkfish Lophius americanus during summer. In inshore regions of eastern Newfoundland, gillnets set for Atlantic cod near breeding colonies resulted in high bycatch rates of murres Uria spp. and shearwaters during summer. High bycatch rates were also observed in pelagic longline fisheries along the Scotian Shelf. While the observer data have highlighted several localized areas with high bycatch rates, information for inshore gillnet fisheries, which take seabirds but are poorly covered by the observer programme, and regional information on fishing effort must both be considered for comprehensive assessment of seabird risk areas and consequent management needs in eastern Canada. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Results of testing three types of streamer lines for reduction of seabird bycatch in demersal longline fishery

The streamer lines of 3 types are tested and compared: i) the model used in the USA Pacific waters; and ii-iii) two new models made of cheaper materials, more accessible in Russia. One new model is similar to the American one but the lateral orange 1/4” Kraton thermoplastic tubes are replaced by orange twisted polyethylene ropes with the diameter 10 mm. Another new model is similar with the former one but its 6 first longest streamers are single instead of double and 1-4 bunches of the yellow polypropylene packing tape (in 6 tapes of 1 m length) are fixed on them. The testing was realized aboard two mid-tonnage vessels for demersal longline fishery in the Far-Eastern Seas of Russia in July-October 2010 and July-August 2013. In total, 223 control longlines with 2 million hooks were set up. The seabird bycatch and frequency of the bird attacks to the bait did not differ significantly between the new models of streamers and the American model, and considerable distinctions in their running abilities were not found, as well, so the streamer lines of easy accessible and cheap materials, able for assembling directly aboard fishing vessels, could be recommended for Russian fishermen for reducing their maintenance charges. Such streamer lines are offered for application to demersal longline fishery in the Far-Eastern Seas of Russia.

Long-term studies of Crozet Island killer whales are fundamental to understanding the economic and demographic consequences of their depredation behaviour on the Patagonian toothfish fishery

AbstractThis paper provides a synthesis of results obtained as part of a long-term collaborative study involving biologists, fishers, and resource managers—centring on the occurrence of killer whales in the Crozet Archipelago before and after the implementation of a demersal longline fishery for Patagonian toothfish. Depredation behaviour was reported as soon as the fishery was initiated, with dramatic effects on both the demographic trajectories of the killer whales and on the amount of fish lost by the fishers. Killer whales interacting with the fishery exhibited very high mortality rates when illegal fishing took place, while killer whales not interacting were unaffected. However, after illegal fishing ended, killer whales interacting with the fishery exhibited both higher fecundity and survival rates compared with killer whales not interacting. Since whales typically removed fish entirely from the hooks, an adapted methodology that did not rely on determining the number of damaged fish was developed to estimate depredation rates. In the Crozet EEZ over a 10-year period, 33.9% of the total amount of Patagonian toothfish caught, representing a total of 28 million €, was estimated to be lost due to the combined effects of killer whale and sperm whale depredation. In an effort to reduce depredation losses, modifications to fishing methods, such as changing the fishing season, changing fishing areas when exposed to depredation and changing longline length and hauling speed were successfully tested. Acoustic deterrent devices were ineffective in deterring killer whales from depredating longlines. Alternative fishing gears, such as fish pots, were also tested. However, while providing encouraging results regarding the suppression of depredation and seabird bycatch, fish pots were not efficient enough to sustain an economically viable fishery. In conclusion, we discuss how the findings of this comprehensive study can be used elsewhere in fisheries confronted with depredation.

Modeling spatial patterns of rare species using eigenfunction-based spatial filters: An example of modified delta model for zero-inflated data

Data of rare species usually contain a high percentage of zero observations due to their low abundance. Such data are generally referred as zero-inflated data. Modeling spatial patterns in such data has been challenging, especially when large datasets are involved and intensive computing are required. The eigenfunction-based spatial filtering provides a flexible tool that allows the existing modeling approaches that can handle zero-inflated data such as the delta model to be applied in the presence of spatial dependence. With a real dataset, the longline seabird bycatch data, the present study demonstrated a modification of delta model with the spatial filters to investigate spatial patterns in zero-inflated data for rare species. We explored a total of 108 spatial weighting matrices, and modified the delta model by incorporating the spatial filters generated from the best spatial weighting matrix. We applied the five-fold cross-validation to compare performance of the modified delta model with other three candidate models based on the mean absolute error and the mean bias. The three candidate models included the baseline model without spatial dependence considered, the trend-surface generalized additive model and the random areal effect model. The delta model modified with spatial filters showed superior performance over the other three candidate models in the seabird bycatch example. With the seabird bycatch example, we illustrated a modification of delta model with the eigenfunction-based spatial filters to investigate spatial patterns. This study provides an alternative to incorporate spatial dependence in the existing approaches for modeling spatial patterns in zero-inflated data for rare species.

Minimizing seabird by‐catch in industrial fisheries

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery; other Commentaries on this paper: Challenges in seabird by‐catch mitigation and the Response from the authors: Problems and solutions for seabird bycatch in trawl fisheries

Problems and solutions for seabird bycatch in trawl fisheries

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery and the Commentaries on this Feature Paper: Minimizing seabird by‐catch in industrial fisheries; Challenges in seabird by‐catch mitigation

Challenges in seabird by‐catch mitigation

Read the Feature Paper: Significant reductions in mortality of threatened seabirds in a South African trawl fishery; other Commentaries on this paper: Minimizing seabird by‐catch in industrial fisheries and the Response from the authors: Problems and solutions for seabird bycatch in trawl fisheries

Seabird bycatch in Portuguese mainland coastal fisheries: An assessment through on-board observations and fishermen interviews

Competition with fisheries and incidental capture in fishing gear are the major current threats for seabirds at sea. Fishing is a traditional activity in Portugal and is mainly composed of a great number of small vessels. Given the lack of knowledge on effects of the Portuguese fishing fleet on seabird populations, bycatch was assessed in mainland coastal waters for 2010–2012. Interviews and on-board data were divided into 5 strata, according to fishing gear: Bottom trawling, Bottom longline, Purse seine, Beach seine, Polyvalent (≥12 m) and Polyvalent (<12 m). Polyvalent included Setnets, Traps and Demersal longlines. Overall, 68 birds were recorded to be bycaught. The average catch per unit effort (CPUE) was 0.05 birds per fishing event. Polyvalent (<12 m), Polyvalent (≥12 m) and Purse seiners had the biggest seabird bycatch rates, with 0.5 (CPUE=0.1), 0.11 (CPUE=0.05) and 0.2 (CPUE=0.11) birds per trip, respectively. Within Polyvalent gear, Setnets captured the largest diversity of seabird species (CPUE=0.06), while Demersal longline had the highest CPUE (0.86). Northern gannet was the most common bycaught species. Although more observation effort is required, our results suggest that substantial numbers of Balearic shearwater might be bycaught annually, mainly in Purse seine and Setnets.