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The observed number of captures (dark grey triangles) and mean estimated captures (black squares; error bars = 95% confidence interval) per year of New Zealand sea lions in the Auckland Islands squid fishery from 1995/96 to 2010/11. The % observer coverage (light grey circles) is also shown. Data taken from Thompson et al. (2013).
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Context 1
... incidence of sea lion mortality in the Auckland Islands squid fishery has been monitored by government observers since 1988 (Wilkinson et al., 2003), although observer coverage has varied from less than 10% to 99% (Fig. 2). The mean estimated level of bycatch peaked in the mid to late 1990s (specifically at 131 in 1995/96 and at 142 in 1996/97; Thompson et al., 2013). As a result, sea lion conservation management has focused on this fishery, with a number of research projects commissioned to assess the impacts of sea lion bycatch and the development and ...
Context 2
... implementation of the SLED as a mitigation measure has attracted controversy. Sea lion bycatch dropped substantially in the Auckland Islands squid fishery following the introduction of SLEDs which were in widespread use by 2004/05 (Fig. 2). How- ever, the continued decline in the estimated sea lion population from 2004/05 to 2008/09 (when the lowest pup production was reported) led to concerns that fisheries-related mortality contin- ued to be an issue for this species (Chilvers, 2012b;Robertson and Chilvers, 2011). This was based on claims that some animals enter- ing a ...
Context 3
... the implementation of mitigation techniques, including the widespread deployment of SLEDs, there has been an encour- aging reduction in the sea lion bycatch reported for the Auckland Islands squid fishery ( Fig. 2; Thompson et al., 2013). It is considered that the risk of sea lions dying in the net and falling out of the escape hole and, therefore, not being included in reported fisheries-related bycatch observations is unlikely (although there has been no spe- cific work to address this) due to the SLED configuration, primarily the fitting of a ...
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... Lack of reported quantifiable interactions may occur for a variety of reasons. These reasons include: that fisheries and pinnipeds are targeting different resources in an area so do not interact; insufficient prey abundance to support large pinniped populations due to overexploitation from fisheries 53 ; that alternative conflict management strategies such as culls and hunting have already been implemented (e.g., ref. 54); or a focus on bycatch or other interactions 55 . Missing quantifiable interactions may also reflect a lack of resources in different regions to conduct research into the topic or that this research is conducted by government agencies and reported in the grey literature. ...
Recent population recovery of many pinniped species (seals, sea lions, walrus) is a conservation success. However, pinniped population recovery combined with increasing global fisheries operations is leading to increased conflicts between pinnipeds and fisheries. This human-wildlife conflict threatens pinniped conservation outcomes and may impose damaging impacts on fisheries, but the economic consequences and extent of these impacts are poorly understood. Here, we provide a global assessment of pinniped and fisheries operational interactions. We show that a third of reported fishing days have interactions with pinnipeds and 13.8% of catch is lost. Our results also reveal high heterogeneity between studies. Small-scale fisheries are three times more likely to interact with pinnipeds and lose four times as much catch as large-scale fisheries. Finally, we develop a spatial index that can predict where conflict is most likely to occur. Our findings reveal a substantial global issue requiring appropriate management as pinniped populations continue to recover.
... Technical solutions, in the form of turtle excluder devices, have been shown to be very effective at reducing turtle bycatch (Magnuson et al., 1990 ) (Jenkins, 2012 ). Similarly, excluder devices for marine mammal bycatch have been implemented and shown to be effective (Hamilton and Baker, 2015 ). A significant obstacle in bycatch reduction has been the limited uptake by fishers of remedial changes proposed that they consider inconvenient and costly (Suuronen, 2022 ). ...
Mobile bottom contact gear such as trawls is widely considered to have the highest environmental impact of commonly used fishing gears, with concern about impact on benthic communities, bycatch, and carbon footprint frequently highlighted as much higher than other forms of fishing. As a result, the use of such gears has been banned or severely restricted in some countries, and there are many proposals to implement such restrictions elsewhere. In this paper, we review the sustainability of bottom trawling with respect to target-species sustainability, impact on benthic communities, bycatch and discards, carbon footprint from fuel use, and impact on carbon sequestration. We compare the impact to other forms of fishing and other food production systems. We show that bottom-trawl and dredge fisheries have been sustained, and where well managed, stocks are increasing. Benthic sedimentary habitats remain in good condition where fishing pressure is well managed and where VME and species of concern can be protected by spatial management. Bycatch is intrinsically high because of the mixed-species nature of benthic communities. The carbon footprint is on average higher than chicken or pork, but much less than beef, and can be much lower than chicken or pork. The impact on carbon sequestration remains highly uncertain. Overall, the concerns about trawling impacts can be significantly mitigated when existing technical gear and management measures (e.g. gear design changes and spatial controls) are adopted by industry and regulatory bodies and the race-to-fish eliminated. When these management measures are implemented, it appears that bottom trawling would have a lower environmental impact than livestock or fed aquaculture, which would likely replace trawl-caught fish if trawling was banned. A total of 83 bottom-trawl fisheries are currently certified by the Marine Stewardship Council, which is the most widely accepted measure of overall sustainability.
... Fishing gear may be modified to reduce interactions with pinnipeds or to allow animals to self-release when they become hooked or entrapped (FAO 2021). There are many possible physical modifications, but seal excluder devices (SEDs) are the most commonly used to prevent pinniped bycatch (Hamilton & Baker 2015). SEDs consist of a grid that allows the target catch to pass through to the codend of a trawl net, but prevents access by pinnipeds. ...
... SEDs consist of a grid that allows the target catch to pass through to the codend of a trawl net, but prevents access by pinnipeds. The grid is placed inside the net, before the codend, at an angle, so that pinnipeds approaching the grid are directed towards an escape opening (hole) through which they can exit the net (Hamilton & Baker 2015, FAO 2021. This technique has been tested on various species of pinnipeds, such as the grey seal (Königson et al. 2015), the New Zealand sea lion Phocarctos hookeri (Hamilton & Baker 2015) and the Australian sea lion (Lyle et al. 2016). ...
... The grid is placed inside the net, before the codend, at an angle, so that pinnipeds approaching the grid are directed towards an escape opening (hole) through which they can exit the net (Hamilton & Baker 2015, FAO 2021. This technique has been tested on various species of pinnipeds, such as the grey seal (Königson et al. 2015), the New Zealand sea lion Phocarctos hookeri (Hamilton & Baker 2015) and the Australian sea lion (Lyle et al. 2016). These studies demonstrated that the risk of pinniped mortality is significantly reduced when SEDs are used, since most of the pinnipeds are observed to exit the net through the opening in apparently good condition (Hamilton & Baker 2015). ...
1. The main issue affecting the conservation of most pinniped species has been identified as interactions with fisheries and aquaculture. In South American waters in particular, this problem has not been well evaluated. Consequently, there is an urgent need for research and conservation measures to address the problem, particularly for species of conservation concern.
2. In this study, we reviewed published and unpublished research and observations from the last 25 years on operational and biological interactions between pinnipeds and fisheries and salmonid aquaculture activities in South American waters, and the onservation and management implications of these interactions in the near future.
3. Two species of pinnipeds are primarily involved in biological and operational interactions with fisheries and aquaculture in South America: the South American sea lion Otaria flavescens and the South American fur seal Arctocephalus australis. Although phocids are present in South American waters, there is no published research on conflicts between phocids and human activities.
4. Interactions between fisheries and pinnipeds have been reported by many countries. In South American waters, interactions mostly involve male and subadult male South American sea lions. However, despite the high frequency of interactions, the estimated economic losses to fisheries and aquaculture related to sea lion depredation are generally low.
5. Incidental capture and mortality of pinnipeds has been reported, especially in artisanal gillnet fisheries and in industrial purse seine and trawl fisheries. Mortality of sea lions in salmonid aquaculture has been reported, but the magnitude of the problem is unknown.
6. In South America, limited progress has been made to incorporate mitigation measures, such as time-area closures, acoustic deterrent devices, and modifications to fishing gear, into fisheries and aquaculture. This is likely to be due to our limited understanding of ecosystem complexity, the costs of modifying fishing gear or incorporating acoustic deterrent devices, and the scarcity
of fishing controls. We suggest that strategies for effectively reducing conflicts between pinnipeds, fisheries, and aquaculture should involve all stakeholders in participative research to facilitate co-management.
... Broad economic incentives (Kearney, 2001;Mansfield, 2006 Reflectors for nets (Jefferson and Curry, 1996;Kastelein et al., 2000) 2 0 2 0 2 0 (continued on next page) (Table 4). Indeed, non-compliance was the most common threat found for all categories, whereas community engagement was Seal exclusion device (Bellchambers et al., 2014*;Hamilton and Baker, 2015;Königson et al., 2015) 3 Total (no and %) 9 3 (33%) 7 (78%) 1 (11%) 6 (67%) 5 (56%) the main opportunity towards achieving successful plans ( Table 4). Moreover, law enforcement and government aid were also considered as important opportunities (Table 4). ...
Small-scale fisheries (SSF) are often considered sustainable; but comprise 95% of global fishers and cumulatively evoke substantial ecosystem impacts that include collateral mortalities. Marine mammals and sea turtles are particularly vulnerable to SSF and have been the focus of conservation strategies. However, many strategies have fallen short of objectives. This study aimed to elucidate and help resolve associated issues by: compiling global efforts to mitigate marine-mammal and sea-turtle bycatches/mortalities among SSF; identifying successful outcomes and influencing factors; and then suggesting steps for mitigating remaining problems. Among 150 articles, there was exponential temporal output, with gillnets the most studied gear (67%). Approximately 71% of all publications proposed mitigation measures but of these, efficacy was assessed in fewer than 2/3. While essential for conservation, community engagement was poorly initiated—although relevant studies have increased in the last decade, which may be correlated with studies describing management approaches instead of typical bycatch assessments. Mitigation measures were assessed in a ‘strength-weaknesses-opportunities-and-threats’ analysis. Mitigation measures should benefit multiple species (‘strengths’), avoid high costs/maintenance (‘weaknesses’), be supported by community engagement and governmental aid/enforcement (‘opportunities’), and consider non-compliance (‘threats’). Collateral mortalities can be reduced among SSF, but regional adoption of technology requires impetus that is best achieved via community engagement.
... The fishery was certified as sustainable by the Marine Stewardship Council (MSC) in 2012 (MSC, 2018), with a range of bycatch mitigation measures implemented including offal management protocols and the cessation of trawling in the vicinity of large numbers of sea lions (Deepwater Group, 2017a). A 2013 peak in bycatch of 21 males led to an "expedited audit," as per MSC Certification Requirements, resulting in all vessels installing Sea Lion Exclusion Devices (SLEDs) (Hamilton and Baker, 2015a) and employing 100% observer coverage (Deepwater Group, 2017b;MSC, 2018) (Figure 3). ...
... The conservation management of the Auckland Islands' population has been controversial and highly debated, with a range of modelling undertaken to assess impacts on this population (Breen et al., 2012;Chilvers, 2012a, b;Roberts et al., 2014;Hamilton and Baker, 2015a, b;Meyer, Davidson, et al., 2015;Robertson, 2015;Hamilton and Baker, 2016a, b;Meyer et al., 2016;Middleton and Breen, 2016;Roberts and Doonan, 2016;Meyer et al., 2017Meyer et al., , 2018Roberts et al., 2018). While there has been focused attention on the role that fisheries bycatch impacted the Auckland Islands' population, there is agreement that no single factor has been solely responsible for this population's decline (Hamilton and Baker, 2016a;Roberts and Doonan, 2016;DoC and MPI, 2017) and, furthermore, bycatch has been effectively mitigated Baker, 2015a, 2016a;DoC and MPI, 2017;Roberts et al., 2018). ...
The endangered New Zealand sea lion, Phocarctos hookeri is killed as incidental bycatch in a trawl fishery operating near their second largest population on Campbell Island in New Zealand’s sub-Antarctic. Using the Potential Biological Removal (PBR) procedure to assess the sustainability of this bycatch for the sea lion population on Campbell Island indicated that annual bycatch estimates, particularly following the implementation of bycatch mitigation measures, are below the PBR threshold of 25 (derived using a precautionary approach). Preliminary Population Viability Analysis (PVA) modelling supported the finding that current bycatch levels, especially given a strong male bias (98%) in bycatch, are sustainable for this population. Models showed that reducing pup mortality through management actions, such as installing ramps in wallows where large numbers of pups drown, would lead to increased population growth. While obtaining more accurate data on population status and demographic parameters for the Campbell Island population should be a priority, this will take many years of research. The PBR and PVA tools demonstrate that contemporary conservation management should continue to focus on increasing pup survival while maintaining mitigation approaches that have reduced bycatch to low levels, together with high observer coverage to sustain confidence in annual bycatch estimates.
... The exit probability describes the chance of sea lions exiting the trawl net via the SLED opening. Previous experiments (predominantly carried out in 2001) implied that the exit probability is high (e.g. as described in Hamilton & Baker (2015)). Since 2001, several SLED designs have been tested leading to a wide-spread use of standardized and approved SLEDs since the 2008 season (Ministry for Primary Industries 2019; Cleal et al. 2007). ...
... In Hamilton and Baker (2016; originally published on-line on Early View October 2014) we undertook population viability analysis (PVA) modelling of the Auckland Islands New Zealand sea lion (NZSL) population. Substantial mitigation, including the development and implementation of a sea lion excluder device (SLED), has been assessed and widely accepted as effective in greatly reducing the bycatch of NZSL in the Auckland Islands squid trawl fishery (MPI, 2014;Hamilton and Baker, 2015). Our modelling results indicated that, with this reduced bycatch level, Auckland Islands trawl fisheries are unlikely to be having a significant direct impact on the Auckland Islands NZSL population. ...
... Furthermore, they recommend that management 'focus on reducing bycatch by minimizing fishery overlap with sea lions and improving the understanding and efficacy of sea lion exclusion devices.' However, they produce no evidence that significant numbers of NZSL are currently being killed in the fishery and make no reference to the substantial efforts and research on SLED efficacy (see MPI, 2014;Hamilton and Baker, 2015). There is now widespread agreement amongst key experts that mitigation measures have led to a significant reduction in bycatch in the Auckland Island trawl fisheries (MPI, 2014). ...
... Physical barriers such as wire grids mounted on the fish traps may prevent seals from entering the traps Lehtonen & Suuronen, 2004;Hemmingsson et al., 2008;Königson et al., 2015b). Exclusion devices that facilitate the seals' exit from the fishing gear (Hamilton & Baker, 2015) or techniques for trapping the seals alive inside the fishing gear have also been developed (Lehtonen & Suuronen, 2010). Small-scale coastal fishermen using trap nets, gill nets and long lines in the Baltic Sea are highly susceptible to seal-induced damage (Köningson et al., 2009), and this is one reason why certain alternative types of seal-proof fishing gear have been developed. ...
... arrow squid (Nototodarus sloanii)] and catch NZSLs as bycatch (Chilvers et al. 2011;Wilkinson et al. 2003). Although bycatch reduction measures have been consistently used in the commercial fisheries since 2005 (Hamilton and Baker 2015), the NZSL population decline has continued (Chilvers 2012b). Therefore, the impact of these threats and the efficacy of conservation actions remain unclear (Robertson and Chilvers 2011) and several population models have produced conflicting results about the effect of epidemics and fisheries bycatch on the NZSL population (e.g. ...
... Across the Auckland Islands shelf, a range of 15 (95 % CI 5-29) to 194 (95 % CI 100-356) NZSLs interacted with trawl nets between 1996 and 2011 (Thompson et al. 2013). Studies on the survival likelihood of bycaught NZSLs (for a review see Hamilton and Baker 2015) have not quantified how many dead NZSLs fall out of the trawl net through SLEDs nor are numbers of individuals known that die (e.g. through head injuries) after escaping a trawl net (Robertson 2015 in press). Compared to that high uncertainty in SLED efficacy, we found that a relatively small increase in adult survival (on average 7 %) would be enough to stop the population decline. ...
Understanding the life history basis of the population dynamics of threatened species is crucial to their assessment and recovery. Within the Southern Pacific Ocean, the decline and range contraction of New Zealand sea lions (NZSLs) (Phocarctos hookeri) are an exemplary case of a major fisheries and conservation controversy. Despite the use of bycatch reduction measures, the main population of the NZSL has declined since 1998 and its vulnerability to threats is poorly understood. Here we develop a population model for the declining population of the endangered NZSL at the Auckland Islands, New Zealand (50∘30′S,166∘17′E), parameterised by mark-recapture data of 2928 female NZSLs spanning 15 years from 1998 to 2012, and provide the first comprehensive analysis of NZSL population dynamics and its relationship to life history. Our model closely predicts the observed trend in population censuses of the main breeding population. We found that the population will continue to decline without effective intervention. Furthermore, we found that the population growth rate is most responsive to changes in survival of adult female NZSLs—the demographic group that is most threatened by fishery bycatch. Nevertheless, inferences about the efficacy of NZSL bycatch reduction measures are still imprecise. Combined, this could explain why the main population of NZSLs continues to decline. Our results emphasise that reliable data on bycatch reduction measures are needed, if they are to be shown to protect key demographic groups of marine mammals.
... For example, physical barriers mounted on the fish traps, such as wire grids, prevent seals from entering the trap [6][7][8]. Alternatively, exclusion devices that facilitate the seals' exit from the fishing gear [9] and techniques that trap seals alive inside the gear have also been developed [10]. ...
Developing methods to reduce the incidental catch of non-target species is important, as by-catch mortality poses threats especially to large aquatic predators. We examined the effectiveness of a novel device, a "seal sock", in mitigating the by-catch mortality of seals in coastal fyke net fisheries in the Baltic Sea. The seal sock developed and tested in this study was a cylindrical net attached to the fyke net, allowing the seals access to the surface to breathe while trapped inside fishing gear. The number of dead and live seals caught in fyke nets without a seal sock (years 2008-2010) and with a sock (years 2011-2013) was recorded. The seals caught in fyke nets were mainly juveniles. Of ringed seals (Phoca hispida botnica) both sexes were equally represented, while of grey seals (Halichoerus grypus) the ratio was biased (71%) towards males. All the by-caught seals were dead in the fyke nets without a seal sock, whereas 70% of ringed seals and 11% of grey seals survived when the seal sock was used. The seal sock proved to be effective in reducing the by-catch mortality of ringed seals, but did not perform as well with grey seals.