Genetic connectivity and hybridization with its siter species challenge the current management paradigm of white anglerfish (Lophius piscatorius)

Understanding the inter and intraspecific dynamics of fish populations is essential to promote effective management and conservation actions and to predict adaptation to changing conditions. This is possible through the analysis of thousands of genetic markers, which has proven useful to resolve connectivity among populations. Here, we have tackled this issue in the white anglerfish (Lophius piscatorius), which inhabits the Northeast Atlantic and Mediterranean Sea and coexists with its morphologically almost identical sister species, the black anglerfish (L. budegassa). Our genetic analyses based on 16,000 SNP markers and 700 samples reveal that i) the white anglerfish from the Mediterranean Sea and the Atlantic Ocean are genetically isolated, but that no differentiation can be observed within the later, and that ii) black and white anglerfish naturally hybridize, resulting in a population of about 20% of, most likely sterile, hybrids in some areas. These findings challenge the current paradigm of white anglerfish management, which considers three independent management units within the North East Atlantic and assumes that all mature fish have reproductive potential. Additionally, the northwards distribution of both species, likely due to temperature raises, calls for further monitoring of the abundance and distribution of hybrids to anticipate the effects of climate change in the interactions between both species and their potential resilience

A NOVEL INDEX OF ABUNDANCE OF JUVENILE YELLOWFIN TUNA IN THE ATLANTIC OCEAN DERIVED FROM ECHOSOUNDER BUOYS

The collaboration with the Spanish vessel-owners associations and the buoy-providers companies, has made it possible the recovery of the information recorded by the satellite linked GPS tracking echosounder buoys used by the Spanish tropical tuna purse seiners and associated fleet in the Atlantic since 2010. These instrumental buoys inform fishers remotely in real-time about the accurate geolocation of the FAD and the presence and abundance of fish aggregations underneath them. Apart from its unquestionable impact in the conception of a reliable CPUE index from the tropical purse seine tuna fisheries fishing on FADs, echosounder buoys have also the potential of being a privileged observation platform to evaluate abundances of tunas and accompanying species using catch-independent data. Current echosounder buoys provide a single acoustic value without discriminating species or size composition of the fish underneath the FAD. Therefore, it has been necessary to combine the echosounder buoys data with fishery data, species composition and average size, to obtain a specific indicator. This paper presents a novel index of abundance of juvenile yellowfin tuna in the Atlantic Ocean derived from echosounder buoys for the period 2010-2018

Evidence of stock connectivity, hybridization and misidentification in white anglerfish support the need of a genetics-informed fisheries management framework

Understanding population connectivity within a species as well as potential interactions with its close relatives is crucial to define management units and to derive efficient management actions. However, although genetics can reveal mismatches between biological and management units and other relevant but hidden information such as species misidentification or hybridization, the uptake of genetic methods by the fisheries management process is far from having been consolidated. Here, we have assessed the power of genetics to better understand the population connectivity of white (Lophius piscatorius) and its interaction with its sister species, the black anglerfish (Lophius budegassa). Our analyses, based on thousands of genome-wide single nucleotide polymorphisms, show three findings that are crucial for white anglerfish management. We found (i) that white anglerfish is likely composed of a single panmictic population throughout the Northeast Atlantic, challenging the three-stock based management, (ii) that a fraction of specimens classified as white anglerfish using morphological characteristics are genetically identified as black anglerfish (L. budegassa), and iii) that the two Lophius species naturally hybridize leading to a population of hybrids of up to 20% in certain areas. Our results set the basics for a genetics-informed white anglerfish assessment framework that accounts for stock connectivity, revises and establishes new diagnostic characters for Lophius species identification, and evaluates the effect of hybrids in the current and future assessments of the white anglerfish. Furthermore, our study contributes to provide additional evidence of the potentially negative consequences of ignoring genetic data for assessing fisheries resources.Versión del editor4,91

Monitoring of discarding and retention by trawl fisheries in Western Waters and the Irish Sea in relation to stock assessment and technical measures

Westem Waters fisheries face major challenges in relation to the depleted state of the fishery resources and in implementing the adjustments required to bring exploitation of these resources on to a more sustainable basis. Fisheries assessments, as carried out by ICES working groups, use data from market sampling of the landed catch, reported landings and effort figures and also research vessel data to assess the state of fish stocks and to produce short term forecasts for setting Total Allowable Catches. Since the discards may constitute a significant source of extra mortality in some fisheries there is clearly a requirement to adequately describe the levels of discarded fish in order to improve stock assessment and the likelihood of sustainability. In deciding a strategy for improved sustainability there is also a requirement to understand the factors motivating the fishers to target and retain, or discard, fish of a given species and to relate this to the current management and market situation. This, and stock assessment information, could be used to guide research into the most appropriate technology and measures to reduce discarding and hence place the harvesting of these stocks on a more sustainable basis. The project studied the pattem of discarding and retention, using an onboard observer programme, in the main demersal trawl fisheries of the participating nations' in Westem Waters (ICES Divisions VIa,b VIIa,b,c,e(western part), f,g,h and k and from VIIIa,b,c,d and IXa) and describes the use of these data in ICES stock assessments. It assessed the feasibility of using these data to understand the economic aspects of discarding and retention, to assess the impact of technical measures and investigated the effects of trawling on ecosystems. Data on discarded megrim from Spanish Baka trawlers were used in the assessment of the Northem Stock of this species at the ICES Southem Shelf Demersal Working Group. These results show that including discard data in the assessment improved the description of the strength of incoming year classes, growth and spawning stock biomass. The impact of technical measures designed to reduce discarding was assessed by examining the effect of the implementation of EC regulation 850/98 on Jan 1st 2000. In the midwater demersal trawl fishery in the Irish Sea there was a reduction in the catch per effort of discarded and retained whiting. For the baka trawlers exploiting megrim in Sub areas VI and VII there was a change in the discarding practices. Discarding and retention is discussed in relation to economic factors and the exploitation pattem. Possible changes in some métiers were suggested but the very mixed nature some of the fisheries means that what is selective for one species could result in the loss of economically important catch of other species. It was found that discarding practices were most closely related to economic values, which were a stronger influence than fishery management measures. Measures which are designed to reduce discarding without taking into account market forces, are unlikely to succeed. Limited studies of the impact of technical measures were carried out by developing a model designed to predict the returns which could be obtained by improving selectivity, but these were intended only to develop the model not to use it on Westem Waters fisheries during this project