Underwater noise recognition of marine vessels passages: two case studies using hidden Markov models

Passive acoustic monitoring (PAM) is emerging as a cost-effective non-intrusive method to monitor the health and biodiversity of marine habitats, including the impacts of anthropogenic noise on marine organisms. When long PAM recordings are to be analysed, automatic recognition and identification processes are invaluable tools to extract the relevant information. We propose a pattern recognition methodology based on hidden Markov models (HMMs) for the detection and recognition of acoustic signals from marine vessels passages and test it in two different regions, the Tagus estuary in Portugal and the Öresund strait in the Baltic Sea. Results show that the combination of HMMs with PAM provides a powerful tool to monitor the presence of marine vessels and discriminate different vessels such as small boats, ferries, and large ships. Improvements to enhance the capability to discriminate different types of small recreational boats are discussed.info:eu-repo/semantics/publishedVersio

Frameless-Finding and Refining A Sampling Frame for Surveying Recreational Fisheries: Lessons from Estimating Swedish Harvest of Western Baltic Cod

To achieve sustainable fisheries, advice to management should be based on reliable science and unbiased data. Attaining quality data (i.e. precise and unbiased) on recreational fishing can be challenging, particularly when prior knowledge of the sector is limited and a proper sample frame of recreational fishers or vessels does not exist. In this study, a registry of access points was constructed for the Swedish south–west coast and used as a spatial sample frame in determining both effort and catches of the private boat fishery. Sampling dates, times for sampling, and access points visited were selected using probabilistic methods, ensuring unbiased results. The final multi-stage sampling design involved multiple strata, clusters, and probability selection methods and enabled first-time estimation of Swedish recreational landings of western Baltic cod by private boats to be used in stock assessment. Concurrent data collection covering aspects such as boat counts at access points, provided additional information on e.g. activity patterns. That additional information opens possibilities to refine the design of the original survey and optimize the sampling effort towards different goals, such as other fished resources. In this paper, we reflect on the challenges that limitations in initial information poses to the design and deployment of a new recreational fisheries survey. We suggest ways, whereby indirect sampling frames can be developed from initially incomplete or limited information to access the fishers and their catch. Our experience shows that, despite initial frame and knowledge limitations, full probabilistic methods are worth considering in data limited scenarios and that the design-based point estimates and variances they provide on recreational fishing effort and catches are useful in guiding initial management and the next steps of survey improvement

First tagging data on large Atlantic bluefin tuna behaviour in newly retaken Nordic areas suggests repeated behaviour and skipped spawning

Atlantic bluefin tuna (Thunnus thynnus; ABFT) is one of the most iconic fish species in the world. Recently, after being very rare for more than half a century, large bluefin tunas have returned to Nordic waters in late summer and autumn, marking the return of the largest predatory fish in Nordic waters. By tagging 18 bluefin tunas with electronic tags (pop-up satellite archival tags), we show that bluefin tuna observed in Nordic waters undertake different migration routes, with individuals migrating into the western Atlantic Ocean, while others stay exclusively in the eastern Atlantic and enter the Mediterranean Sea to spawn. We additionally present evidence of possible skipped spawning inferred from behavioural analyses. In Nordic waters, ABFT are primarily using the upper water column, likely reflecting feeding activity. The results support the hypothesis that ABFT migrating to Nordic waters return to the same general feeding area within the region on an annual basis. These observations may have important implications for management because (1) tunas that come into Nordic waters might represent only a few year classes (as evidenced by a narrow size range), and thus may be particularly vulnerable to area-specific exploitation, and (2) challenge the assumption of consecutive spawning in adult Atlantic bluefin tuna, as used in current stock assessment models. Without careful management and limited exploitation of this part of the ABFT population, the species’ return to Nordic waters could be short-lived

Long-term effects of no-take zones in Swedish waters

Marine protected areas (MPAs) are increasingly established worldwide to protect and restore degraded ecosystems. However, the level of protection varies among MPAs and has been found to affect the outcome of the closure. In no-take zones (NTZs), no fishing or extraction of marine organisms is allowed. The EU Commission recently committed to protect 30% of European waters by 2030 through the updated Biodiversity Strategy. Importantly, one third of these 30% should be of strict protection. Exactly what is meant by strict protection is not entirely clear, but fishing would likely have to be fully or largely prohibited in these areas. This new target for strictly protected areas highlights the need to evaluate the ecological effects of NTZs, particularly in regions like northern Europe where such evaluations are scarce. The Swedish NTZs made up approximately two thirds of the total areal extent of NTZs in Europe a decade ago. Given that these areas have been closed for at least 10 years and can provide insights into long-term effects of NTZs on fish and ecosystems, they are of broad interest in light of the new 10% strict protection by 2030 commitment by EU member states.In total, eight NTZs in Swedish coastal and offshore waters were evaluated in the current report, with respect to primarily the responses of focal species for the conservation measure, but in some of the areas also ecosystem responses. Five of the NTZs were established in 2009-2011, as part of a government commission, while the other three had been established earlier. The results of the evaluations are presented in a synthesis and also in separate, more detailed chapters for each of the eight NTZs. Overall, the results suggest that NTZs can increase abundances and biomasses of fish and decapod crustaceans, given that the closed areas are strategically placed and of an appropriate size in relation to the life cycle of the focal species. A meta-regression of the effects on focal species of the NTZs showed that CPUE was on average 2.6 times higher after three years of protection, and 3.8 times higher than in the fished reference areas after six years of protection. The proportion of old and large individuals increased in most NTZs, and thereby also the reproductive potential of populations. The increase in abundance of large predatory fish also likely contributed to restoring ecosystem functions, such as top-down control. These effects appeared after a 5-year period and in many cases remained and continued to increase in the longer term (>10 years). In the two areas where cod was the focal species of the NTZs, positive responses were weak, likely as an effect of long-term past, and in the Kattegat still present, recruitment overfishing. In the Baltic Sea, predation by grey seal and cormorant was in some cases so high that it likely counteracted the positive effects of removing fisheries and led to stock declines in the NTZs. In most cases, the introduction of the NTZs has likely decreased the total fishing effort rather than displacing it to adjacent areas. In the Kattegat NTZ, however, the purpose was explicitly to displace an unselective coastal mixed bottom-trawl fishery targeting Norway lobster and flatfish to areas where the bycatches of mature cod were smaller. In two areas that were reopened to fishing after 5 years, the positive effects of the NTZs on fish stocks eroded quickly to pre-closure levels despite that the areas remained closed during the spawning period, highlighting that permanent closures may be necessary to maintain positive effects.We conclude from the Swedish case studies that NTZs may well function as a complement to other fisheries management measures, such as catch, effort and gear regulations. The experiences from the current evaluation show that NTZs can be an important tool for fisheries management especially for local coastal fish populations and areas with mixed fisheries, as well as in cases where there is a need to counteract adverse ecosystem effects of fishing. NTZs are also needed as reference for marine environmental management, and for understanding the effects of fishing on fish populations and other ecosystem components in relation to other pressures. MPAs where the protection of both fish and their habitats is combined may be an important instrument for ecosystembased management, where the recovery of large predatory fish may lead to a restoration of important ecosystem functions and contribute to improving decayed habitats.With the new Biodiversity Strategy, EUs level of ambition for marine conservation increases significantly, with the goal of 30% of coastal and marine waters protected by 2030, and, importantly, one third of these areas being strictly protected. From a conservation perspective, rare, sensitive and/or charismatic species or habitats are often in focus when designating MPAs, and displacement of fisheries is then considered an unwanted side effect. However, if the establishment of strictly protected areas also aims to rebuild fish stocks, these MPAs should be placed in heavily fished areas and designed to protect depleted populations by accounting for their home ranges to generate positive outcomes. Thus, extensive displacement of fisheries is required to reach benefits for depleted populations, and need to be accounted for e.g. by specific regulations outside the strictly protected areas. These new extensive EU goals for MPA establishment pose a challenge for management, but at the same time offer an opportunity to bridge the current gap between conservation and fisheries management

Förvaltningsmål för nationellt förvaltade fiskbestånd

Fisk- och skaldjursbestånd som i huvudsak är begränsade till svenska nationella vatten förvaltas av svenska myndigheter och organisationer. Dessa bestånd kan i motsats till internationellt exploaterade och förvaltade arter utnyttjas av flera olika aktörer (t.ex. kommersiellt- och fritidsfiske). Olika grupper av aktörer kan ha olika syn på vad som är de lämpligaste långsiktiga förvaltningsmålen (t.ex. stor avkastning vs. stora individer). För dessa nationella bestånd är ofta datatillgången sämre än för in-ternationella bestånd, och ofta saknas tydliga mätbara förvaltningsmål, vilket resul-terar i en mindre effektiv förvaltning. Syftet med denna rapport är att ge en överblick över tillgängliga kvantitativa förvaltningsmål med tillhörande metoder som är lämp-liga för ett långsiktigt hållbart utnyttjande av nationella fisk- och skaldjursbestånd. Vi identifierar tre huvudkategorier av kvantitativa förvaltningsmål: 1) Långsiktigt hållbar avkastning, som kräver detaljerade data från många olika källor. 2) Minini-våer av biomassa- eller abundansindex, eller ett specifikt förhållande mellan fångst och biomassaindex, vilket kräver pålitlig övervaknings- eller fångstdata. 3) "Natur-lik" eller "önskvärd" demografisk struktur, vilket kräver information om egenskaper så som storlek, ålder, och könsmognad. Alla tre typerna av mål har sina förtjänster och nackdelar. Mål för hållbar avkastning och biomassa-index tar inte hänsyn till storleksstruktur, och vice versa, och olika mål kräver olika typer av indata. Vi gör en översikt av vilka förvaltningsmål som kan vara lämpliga för olika typer av nationellt förvaltade fisk- och skaldjursbestånd. För närvarande är aktuella data i allmänhet allt-för begränsade för att föreslå specifika förvaltningsmål för de flesta bestånd som kan komma i fråga för nationell förvaltning. Snarare betonar vi vikten av att använda flera olika mål i stället för att förlita sig på ett enda för att underlätta en hållbar användning av akvatiska resurser med hänsyn tagen till olika intressenter. Dessutom finns det ingen klar definition av vad ett nationellt bestånd är och när det är lämpligt att ha en nationell förvaltning. Därför är det viktigt att förvaltningsmålen sätts så att de kan återspegla både internationella, nationella och lokala förutsättningar

Syntesrapport av Sekretariatet för selektivt fiske 2014-2017

På uppdrag av Havs- och vattenmyndigheten (HaV), som har ansvarat för regeringsuppdraget selektivt fiske, upprättade SLU Aqua ett Sekretariat för selektivt fiske mellan 2014 och 2017. Sekretariatets huvuduppgift har varit att samla in idéer tillsammans med näringen, för att stimulera utvecklingen av selektiva fiskemetoder i syfte att minska mängden oönskad fångst. Näringens initiativ och engagemang har varit helt avgörande för en framgångsrik utveckling av nya idéer. Under projektperioden har sekretariatet tillsammans med näringen drivit 34 projekt inom selektivt fiske. Samtliga projekt är vetenskapligt utvärderade och redovisade i årliga verksamhetsrapporter. I denna syntesrapport sammanställs resultaten från projekt med liknande problemställningar, målarter och fiskemetoder, till olika fisken. De olika fiskena är uppdelade mellan aktiva och passiva redskap. I sammanställningen har alla projekten bedömts efter en 5-gradig skala som sammanfattar resultatet av den vetenskapliga utvärderingen, redskapets tillämpbarhet i verkligt fiske samt behov av förvaltningsåtgärder och/eller andra incitament för att redskapen verkligen skall komma till bred användning i fisket

Sekretariatet för selektivt fiske

Under hösten/vintern 2015/2016 genomförde sekretariatet för selektivt fiske,vid institutionen för akvatiska resurser (SLU-Aqua) tillsammans med svenskt yrkesfiske, nio projekt inom ramen för regeringsuppdraget selektivt fiske. Den övergripande målsättningen för alla projekt inom selektivt fiske är att underlätta införandet av den landningsskyldighet som beslutats i och med reformen av EU:s gemensamma fiskeripolitik. Projekten syftade därför till att minska oönskad fångst i svenskt fiske antingen genom att utveckla befintliga fiskemetoder (framförallt inom trålfiske) eller genom att utveckla alternativa fiskemetoder (främst passiva redskap såsom fällor och burar). 1. "Kombinationsrist för utsortering av fisk och små räkor" (HaV Dnr 1718-15) 2. ”Selektivitet anpassad för små räktrålare” (HaV Dnr 1488-16) 3. "Räkburar” (HaV Dnr 1892-15) 4. ”Vidareutveckling av storleksselektiv kräftrist Halland” (HaV Dnr 1717-15) 5. ”Trål för fångst av plattfisk och stor torsk-rist/stormaskig trål” (HaV Dnr 1716-15) 6. "Förbättrad selektivitet i torsktrålar i Östersjön" (HaV Dnr 2384-15) 7. "Utsortering av gråsej i pelagiska trålar" (HaV Dnr 1715-15) 8. "Selektiv laxfälla" (HaV Dnr 1713-15) 9. "Multifunktionsburar" (HaV Dnr 1712-15) Projekten genomfördes genom att förslag togs fram gemensamt av SLU-Aqua och näringen utifrån fiskets uttryckliga behov och idéer. Projektförslagen prioriterades och beslutades av en särskild styrgrupp på Havs- och vattenmyndigheten (HaV), varefter SLU-Aqua upphandlade utförare och agerade projektledare. Vinnande part ansvarade sedan för att anskaffa och utveckla respektive projektidé enligt projektplanen med stöd från sekretariatet. Projekten avslutades genom en vetenskaplig utvärdering där personal från SLUAqua deltog i ett experimentellt fiske där det nyutvecklade redskapets fångstegenskaper dokumenterades och analyserades under kommersiella fiskeförhållanden

Much ado about nothing: An example of how failed incentives thwarted the implementation of the EU landing obligation

With the introduction of the landing obligation in the EU common fisheries policy, there has been several initiatives to reduce unwanted catches of quota-regulated species. In this study, we present a flexible sorting grid as a potential solution for the problem of bycatch of saithe in the pelagic herring trawl fishery in the Skagerrak. The development of the grid was initiated by the industry and finalised through an industry-science collaboration project. The selectivity of the grid was evaluated through the use of an underwater camera system during conventional trawling with an industrial pelagic herring trawler. The results showed that the grid reduced the bycatch by more than 90%, from approximately 5% to 0.5% of the total catch. Given the scale of the pelagic fishery, this reduction could decrease unwanted bycatch of saithe by up to 1000 tonnes per year in the Skagerrak alone. These results were communicated to national industry and management representatives and to responsible EU management bodies and advisory councils. The work conducted within the project also drew interest at the yearly negotiations between EU and Norway. In their agreement for 2018, the EU and Norway agreed to establish a working group on technical measures in the Skagerrak tasked with reviewing selectivity of pelagic trawls as part of the terms of reference. However, in the agreed record of the delegations, the question of pelagic gear selectivity in the Skagerrak was a non-issue, although they concluded that the demersal bycatch can be substantial, that a sorting grid can reduce this bycatch and a sorting grid remains mandatory for Norwegian vessels in the Skagerrak. We argue that this result can be seen as a missed opportunity for the EU to reduce unaccounted bycatch in the Skagerrak and ensure better implementation of the landing obligation