Population genomics of the white beaked dolphin (Lagenorhynchus albirostris)::Implications for conservation amid climate driven range shifts

Climate change is rapidly affecting species distributions across the globe, particularly in the North Atlantic. For highly mobile and elusive cetaceans, the genetic data needed to understand population dynamics are often scarce. Cold-water obligate species such as the white-beaked dolphin (Lagenorhynchus albirostris) face pressures from habitat shifts due to rising sea surface temperatures in addition to other direct anthropogenic threats. Unravelling the genetic connectivity between white-beaked dolphins across their range is needed to understand the extent to which climate change and anthropogenic pressures may impact species-wide genetic diversity and identify ways to protect remaining habitat. We address this by performing a population genomic assessment of white-beaked dolphins using samples from much of their contemporary range. We show that the species displays significant population structure across the North Atlantic at multiple scales. Analysis of contemporary migration rates suggests a remarkably high connectivity between populations in the western North Atlantic, Iceland and the Barents Sea, while two regional populations in the North Sea and adjacent UK and Irish waters are highly differentiated from all other clades. Our results have important implications for the conservation of white-beaked dolphins by providing guidance for the delineation of more appropriate management units and highlighting the risk that local extirpation may have on species-wide genetic diversity. In a broader context, this study highlights the importance of understanding genetic structure of all species threatened with climate change-driven range shifts to assess the risk of loss of species-wide genetic diversity.</p

Robustness of potential biological removal to monitoring, environmental, and management uncertainties

Support for this project was provided by the Lenfest Ocean Program.The potential biological removal (PBR) formula used to determine a reference point for human-caused mortality of marine mammals in the United States has been shown to be robust to several sources of uncertainty. This study investigates the consequences of the quality of monitoring on PBR performance. It also explores stochastic and demographic uncertainty, catastrophic events, sublethal effects of interactions with fishing gear, and the situation of a marine mammal population subject to bycatch in two fisheries, only one of which is managed. Results are presented for two pinniped and two cetacean life histories. Bias in abundance estimates and whether there is a linear relationship between abundance estimates and true abundance most influence conservation performance. Catastrophic events and trends in natural mortality have larger effects than environmental stochasticity. Managing only one of two fisheries with significant bycatch leads, as expected, to a lower probability of achieving conservation management goals, and better outcomes would be achieved if bycatch in all fisheries were managed. The results are qualitatively the same for the four life histories, but estimates of the probability of population recovery differ.Publisher PDFPeer reviewe

Estimating bycatch mortality for marine mammals : concepts and best practices

Support for this project was provided by the Lenfest Ocean Program (Contract ID: #31008).Fisheries bycatch is the greatest current source of human-caused deaths of marine mammals worldwide, with severe impacts on the health and viability of many populations. Recent regulations enacted in the United States under the Fish and Fish Product Import Provisions of its Marine Mammal Protection Act require nations with fisheries exporting fish and fish products to the United States (hereafter, “export fisheries”) to have or establish marine mammal protection standards that are comparable in effectiveness to the standards for United States commercial fisheries. In many cases, this will require estimating marine mammal bycatch in those fisheries. Bycatch estimation is conceptually straightforward but can be difficult in practice, especially if resources (funding) are limiting or for fisheries consisting of many, small vessels with geographically-dispersed landing sites. This paper describes best practices for estimating bycatch mortality, which is an important ingredient of bycatch assessment and mitigation. We discuss a general bycatch estimator and how to obtain its requisite bycatch-rate and fisheries-effort data. Scientific observer programs provide the most robust bycatch estimates and consequently are discussed at length, including characteristics such as study design, data collection, statistical analysis, and common sources of estimation bias. We also discuss alternative approaches and data types, such as those based on self-reporting and electronic vessel-monitoring systems. This guide is intended to be useful to managers and scientists in countries having or establishing programs aimed at managing marine mammal bycatch, especially those conducting first-time assessments of fisheries impacts on marine mammal populations.Publisher PDFPeer reviewe

Estimating the abundance of marine mammal populations

Support for this project was provided by the Lenfest Ocean Program.Motivated by the need to estimate the abundance of marine mammal populations to inform conservation assessments, especially relating to fishery bycatch, this paper provides background on abundance estimation and reviews the various methods available for pinnipeds, cetaceans and sirenians. We first give an “entry-level” introduction to abundance estimation, including fundamental concepts and the importance of recognizing sources of bias and obtaining a measure of precision. Each of the primary methods available to estimate abundance of marine mammals is then described, including data collection and analysis, common challenges in implementation, and the assumptions made, violation of which can lead to bias. The main method for estimating pinniped abundance is extrapolation of counts of animals (pups or all-ages) on land or ice to the whole population. Cetacean and sirenian abundance is primarily estimated from transect surveys conducted from ships, small boats or aircraft. If individuals of a species can be recognized from natural markings, mark-recapture analysis of photo-identification data can be used to estimate the number of animals using the study area. Throughout, we cite example studies that illustrate the methods described. To estimate the abundance of a marine mammal population, key issues include: defining the population to be estimated, considering candidate methods based on strengths and weaknesses in relation to a range of logistical and practical issues, being aware of the resources required to collect and analyze the data, and understanding the assumptions made. We conclude with a discussion of some practical issues, given the various challenges that arise during implementation.Publisher PDFPeer reviewe

Gelatinous zooplankton in Icelandic coastal waters with special reference to the scyphozoans Aurelia aurita and Cyanea capillata

Á nálægum hafsvæðum virðist fjöldi marglyttna og marglyttutorfa hafa verið að aukast nokkuð undanfarin ár samhliða hlýnun sjávar. Þessir atburður og aukinn skilningur manna á mikilvægi marglyttna í samfélögum uppsjávarins hefur orðið tilefni aukinna rannsókna á marglyttum á nálægum hafsvæðum. Fyrri rannsóknir á marglyttum hér við land fóru fram á árunum milli 1930 og 1940. Því er ljóst að þekking á marglyttum hér við land er komin til ára sinna og þörf á nýjum upplýsingum um líffræði og útbreiðslu þeirra. Sumarið 2007 hófust rannsóknir á líffræði marglyttna við Ísland. Tekin voru sýni á fjórum svæðum við landið, þ.e. í Hvalfirði, í Álftafirði í Ísafjarðardjúpi, í Eyjafirði og í Mjóafirði á Austfjörðum. Árið 2008 var síðan Patreksfirði og Tálknafirði bætt við. Svifsýni voru tekin með Bongóháfi á nokkrum stöðvum í hverjum firði mánaðarlega frá maí til september. Allt hlaupkennt dýrasvif (marglyttur, smáhveljur (hydrozoa) og kambhveljur) var greint til tegunda úr sýnum sem tekin voru í Patreksfirði og Tálknafirði. Frá hinum svæðunum voru einungis marglyttur greindar. Þvermál allra heillegra marglytta var mælt. Árið 2008 fundust ellefu tegundir af smáhveljum (Hydrozoa) í Patreksfirði og Tálknafirði, ein kambhveljutegund (Ctenophora) og tvær tegundir af marglyttum (Scyphozoa) en þessir hópar eru stór hluti þess sem kallað er „hlaupkennt dýrasvif”. Tegundafjöldi var mestur í júní (12 tegundir), en Shannon’s H’ fjölbreytileikastuðullinn var hæstur snemma í maí (~1.5). Algengasta tegundin reyndist vera Clytia sp. Tvær tegundir af marglyttum reyndust algengar, þ.e. bláglytta (Aurelia aurita) og brennihvelja (C. capillata). Mun færri marglyttur veiddust árið 2007 en árið 2008, og á það sérstaklega við um bláglyttu (A. aurita), sem var mjög algeng á flestum svæðum árið 2008, en aðeins fáein eintök fundust árið á undan. Flestar bláglyttur veiddust í september árið 2008 í Eyjafirði (~120 einstaklingar/1000 m3). Mest veiddist hinsvegar af brennihvelju í maí 2008 í Álftafirði (~17 einstaklingar/1000 m3). Árið 2008 var stærðardreifing bláglyttna mismunandi á milli svæða og voru bláglyttur á Vestfjörðum (Álftafjörður, Patreksfjörður og Tálknafjörður) minni en bláglyttur í Hvalfirði og í Eyjafirði. vii Útbreiðsla brennihvelju við landið hefur breyst frá þeim tíma þegar kerfisbundnar rannsóknir voru síðast gerðar við landið á fjórða og fimmta áratug síðustu aldar. Megin útbreiðslusvæði brennihvelju hefur færst norðar og bæði bláglytta og brennihvelja taka að birtast fyrr á vorin. Ekki er ljóst hvað veldur þessari breytingu, en breytingar í hafinu umhverfis landið tengdar hlýindatímabili sem hefur staðið yfir frá því um 1996 eru líklegar til að hafa áhrif á magn og útbreiðslu marglyttna við Ísland. Aðrir þættir sem geta einnig haft áhrif á magn og útbreiðslu marglyttna eru m.a. afrán, samkeppni og ástand botnlæga dvalarstigs marglyttnanna, þ.e. sepans. Niðurstöður rannsóknarinnar benda til, að Vestfirðir séu uppeldisstöðvar fyrir brennihvelju við landið og að þaðan dreifast ungar hveljur með strandstraumnum og hlýsjónum norður og vestur með landinu. Hins vegar er magn af lirfum brennihveljunnar að vori ekki góð vísbending um þéttleika fullorðna hvelja að sumarlagi.AVS rannsóknarsjóður í sjávarútveg

Table_1_Bomb radiocarbon determines absolute age of adult fin whales, and validates use of earplug growth bands for age determination.xlsx

Baleen whales are one of the few vertebrate taxa for which there are no confirmed estimates of longevity or methods of age determination. Lamina counts in the waxy earplug are assumed to represent age, but ageing accuracy is completely unknown. In this study, bomb radiocarbon assays of the earplug growth sequence in three adult fin whales (Balaenoptera physalus) were used to prepare the most complete within-individual bomb radiocarbon chronologies yet reported for any vertebrate. The whale radiocarbon chronologies matched those of known-age carbonate reference chronologies very well, indicating that the earplug laminae were both metabolically stable and formed throughout the life of the whale. Earplug lamina counts accurately represented absolute ages of 65-85 yr to within 6% of the correct age. Detection of a significant declining trend in δ13C with year of lamina formation within individual whales was consistent with that of the Suess effect, again underlining the metabolic stability of the earplug laminae. Given our results, recent applications of earplug laminae for reconstructing diet and life history events appear to be firmly based, with the potential for further elemental and isotopic applications analogous to those of the otolith.</p

Assessing pinniped bycatch mortality with uncertainty in abundance and post-release mortality : a case study from Chile

We acknowledge funding from LENFEST and Project FIPA.The effects of human-caused mortality, such as fisheries bycatch, of endangered, threatened and protected (ETP) species of marine mammals can be evaluated using population model-based stock assessments. The information available to conduct such assessments is often very limited. Available data might include fragmented time-series of abundance estimates, incomplete data on bycatch for the fisheries that interact with ETP species (often few years and low observer coverage), and perhaps some data on scale and trends in fishing effort. Such data are challenging to use as the basis for stock assessments, which generally assume that estimates of removals (bycatch, in our context) through time are available for at least the most recent decade or two. This paper describes a stock assessment method for use with sparse observer data on bycatch mortality, applied within the context of a Bayesian estimation framework. The method produces estimates, with associated measures of precision, of population size and historical time-series of bycatch mortality that are consistent with the observer and abundance data. It provides a rigorous way to account for the uncertainty arising from animals that are caught but released alive and then die subsequent to release, given a post-release mortality rate prior. Observer data from industrial and artisanal purse seine and trawl fisheries and survey data for South American sea lions (Otaria byronia) and South American fur seals (Arctocephalus australis) off Chile are used to illustrate the method.Publisher PDFPeer reviewe