The Society for Marine Mammalogy UK Student Chapter Meeting 2008, Cromarty. Abstracts

Transcription

1 The Society for Marine Mammalogy UK Student Chapter Meeting 2008, Cromarty. Abstracts

2 Time Wed 6 th FEB 7:30-late Event Icebreaker, Cromarty Training Centre Thurs 7 th FEB 10:00-10:45 Paul Thompson, Opening welcome talk 10:45-11:00 Andy Foote 11:00-11:30 Tea/coffee 11:30 12:30 Filipa Samarra Marija Spasikova Caroline Carter 12:30-14:00 Lunch 14:00 15:00 Arliss Winship Line Cordes Ross Culloch 3:00 3:30 Teas/coffee Poster session 3:30-4:30 Holly Fearnbach (via video link to Seattle) Ana Cândido Nina Baumgartner Ruth Garcia Emily Lambert 7:45 onwards Evening meal at the Sutor Creek Followed by a traditional music jam at the Royal Pub next door. 8 th FEB: DAY TWO 10:00-11:00 Cormac Booth Lindesay Scott-Hayward 11-11:30 Tea/coffee 11:30-12:00 Danielle Harris Katie Saunders 12:00-1:00 Lunch 1:00-2:00 Live link up to Dan Nussey s seminar in Aberdeen 2:00-4:00 Luke Rendell s Workshop on funding applications 4:00-4:15 Closing words, choosing next years venue, and new volunteers for the committee.

3 VARIATIONS IN COASTAL MINKE WHALE OCCURRENCE WITH RESPECT TO FOOD AVAILABILITY IN NORTHEAST SCOTTISH WATERS Baumgartner, Nina (1), Robinson, Kevin P. (2), MacLeod, Colin D. (3) and Pierce, Graham J. (4) (1,3,4) School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, Scotland, UK; (1,2) Cetacean Research & Rescue Unit (CRRU), PO Box 11307, Banff AB45 3WB, Scotland, UK The Moray Firth is a summer feeding ground for the northern minke whale (Balaenoptera acutorostrata). Between 2001 and 2007, we studied the summer occurrence of minke whales in the southern outer Moray Firth and examined how the use of this area varied both within and between years. Intra-annually, the occurrence of whales showed a typical increase from May to July and a subsequent decrease from July to September, representing an inshore-offshore movement. This behaviour may be in synchrony with the larval metamorphosis period of the lesser sandeel (Ammodytes marinus) prey, targeted by minkes in this region. While this pattern was consistent between years, the number of whales using the area varied greatly between years. The mean daily sighting rates were 0.1 whales per hour in 2001, 0.03 in 2002, 0.17 in 2003, 0 in 2004, 0.33 in 2005, 0.28 in 2006, 0.11 in There were also variations in observed feeding behaviours and spatial use of the study area, which was interpreted as a consequence of inter-annual variation between hatch-date distributions of sandeels. This inter-annual variation in occurrence is also found in data collected from other areas of the North Sea, and is the inverse of changes seen in western Scotland. This suggests that minke whales shift opportunistically between prey species and summer feeding grounds, according to prey availability. Therefore, our study of minke whale occurrence and behaviour in the coastal Moray Firth may provide information on the driving forces behind wider scale changes in minke whale occurrence in Scottish waters that are important to understand for conservation purposes. INTER-ANNUAL DIFFERENCES IN HARBOUR PORPOISE DISTRIBUTION ON THE WEST COAST OF SCOTLAND Booth, Cormac G. 1 ; Embling, Clare, B. 1 ; Stevick, Peter T. 2 ; Gillespie, Doug 1 ; Gordon, Jonathan 1, Hammond, Philip S. 1 (1) Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB (2) Hebridean Whale and Dolphin Trust, 28 Main Street, Tobermory, Isle of Mull, PA75 6NU Effective conservation requires information on spatial and temporal aspects of a species distribution to identify important habitats and how they vary over time. There have been a number of studies on harbour porpoise (Phocoena phocoena) distribution on the west coast of Scotland in recent years. However, most analysis has focused on spatial variation and how the distribution of harbour porpoise varies at different temporal scales remains poorly known. We investigated inter-

4 annual variations in harbour porpoise distribution and whether there were consistent high-use areas over time on the west coast of Scotland. Visual and acoustic line transect surveys were carried out between April and September from the Hebridean Whale and Dolphin Trust s research vessel Silurian. Survey effort varied between years (range: 3,103 11,170 km) but consistent coverage of a core area was maintained through the study period. Distribution was compared between years by modeling detections per unit effort using a negative binomial generalized linear model (GLM) with a logit link function. Across each of the study years, significantly more porpoises were detected from acoustic surveys than from visual surveys (0.161 and porpoises per kilometre, respectively; p<0.001). There was a slight increase in both visual and acoustic detections over the five years, though this relationship was not significant. Results show that harbour porpoises were found at significant densities throughout the west coast of Scotland. However, there were areas of high use for harbour porpoises, which were consistent over time. For example, detection rates were high in the southeastern region, particularly the Firth of Lorn and Sound of Jura in every year of the study. USE OF T-PODS TO EVALUATE HOW BOTTLENOSE DOLPHINS USE CRITICAL AREAS WITHIN A SPECIAL AREA OF CONSERVATION CÂNDIDO, ANA TERESA (1,2) AND THOMPSON, PAUL M. (1) (1) University of Aberdeen, Lighthouse Field Station, George Street, Cromarty, Ross- Shire IV11 8YJ, Scotland, UK (2) Unidade de Investigação em Eco-Etologia, Instituto Superior de Psicologia Aplicada, R. Jardim do Tabaco, 34, Lisbon, Portugal Conservation plans for cetaceans and the designation of MPAs usually require the definition of critical areas, or hotspots, and rely mostly on sightings data. Such data are normally gathered during relatively infrequent visual surveys that are restricted to daytime, and depend heavily on weather conditions. The use of T-PODs, Timing POrpoise Detectors, can overcome some of the constraints presented by other survey methods, since they can be deployed continuously for long periods of time and work in all weather conditions. The T-POD is an automated passive acoustic device that detects and records cetaceans echolocation clicks. In this study T-PODs were used to analyse seasonal and diurnal patterns in use of space by bottlenose dolphins in the Moray Firth Special Area of Conservation, Scotland, and to test the hypothesis that knowledge about these patterns will affect the definition of critical areas. Three areas of intensive use were originally identified from sightings data ( ). T-POD data collected at these sites between 2005 and 2007 showed clear seasonal patterns, with the highest number of detections occurring between May and August. Contrary to previous findings the higher resolution T-POD data showed that the number of detections increased towards the inner Moray Firth as summer progressed. For the two most intensively used areas there were significant differences in the number of detections during night and day (Wilcoxon Sum of Ranks (Mann-Whitney) test, p<0.05), but the pattern differed between sites. The use of T-PODs can help to expand the range of conditions under which data can be collected, giving additional insight

5 into cetaceans use of space, and providing a more robust framework for conservation strategies. INTER-ANNUAL VARIATION IN THE TIMING OF PUPPING OF INDIVIDUAL FEMALE HARBOUR SEALS (PHOCA VITULINA) CORDES, LINE (1) AND THOMPSON, PAUL M. (1) (1) University of Aberdeen, Lighthouse Field Station, George Street, Cromarty, Ross- Shire IV11 8YJ, Scotland, UK Climate change and changes in food availability have raised concerns over the state of many pinniped populations, requiring a better understanding of the ways in which individuals cope with environmental change. Studies suggest that variation in environmental conditions may cause inter-annual changes in the timing of pupping, but further work is required to confirm that such changes are not the result of difference in age-structure. This study was undertaken to determine the timing of pupping of individual harbour seals in Loch Fleet, Scotland. Pupping dates were obtained by sightings and re-sightings of individual females using photographic identification of the head and neck pelage patterns during the breeding season. These were compared with similar data from the same site collected during Data were also collected on site fidelity, lactation durations, maternal length using digital photogrammetry and pup sex. This group of harbour seals showed high levels of site fidelity both within (10 to 100%) and between (86.5%) seasons, and individual females were consistent in their relative timing of pupping between years (p<0.05). Overall the timing of pupping occurred significantly earlier in 2007 compared to 2006 both for the group (2006, n=31, June 19 th ; 2007, n=25, June 15 th ; p<0.05) and for individual (2006, n=17, June 17 th ; 2007, n=17, June 14 th ; p<0.05) females. This may be explained by reduced food availability in Females who pupped earlier weaned their pups at an older age than females who pupped late in the season (p<0.05), and female pups were born significantly earlier than male pups (n=19, p<0.05). These results suggest that individual-based studies of inter-annual variation in the timing of pupping provide potential for exploring the impacts of environmental variability on harbour seals. INTERACTIONS BETWEEN FINE-SCALE HABITAT, REPRODUCTIVE SUCCESS AND SOCIAL BEHAVIOUR IN GREY SEALS CULLOCH, ROSS University of Durham Previous studies of breeding grey seals have demonstrated that fine-scale habitat features can significantly impact individual behaviour and reproductive success However, the precise link between variation in fine-scale habitat and priority of access to preferred habitat among female grey seals has yet to be determined. Females in better habitat do perform better, but it is as yet unclear whether this is due to the qualities of the habitat, or whether higher quality females monopolise these habitats.

6 An assessment of female interactions specifically with respect to social dominance and habitat use is crucial to resolving this. However, dominance relationships among breeding females is complicated due to the highly context dependent nature of interactions. The aim of my work is to establish a behavioural protocol for quantifying relative dominance status of breeding female grey seals and ultimately to apply this to assess fine scale habitat utilisation with respect to habitat availability and social status. Here, I report on my first field season (September, October and November 2007) where I collected fine scale behavioural data from two small subsets of approximately grey seals within the larger, well established and well known breeding colonies on North Rona and the Farne Islands. This oral presentation aims to discuss the methods used for data collection, the pros and cons of the field sites, as well as the general aims of the Ph.D. MONITORING ABUNDANCE TRENDS OF BAHAMIAN ODONTOCETES (Poster) Dolman, Sarah J. 1, Diane E. Claridge2 and John W. Durban3 1) University of Aberdeen, School of Biological Sciences, Zoology Building, Tillydrone Avenue, Aberdeen AB24 2TZ, Scotland; WDCS, Brookfield House, 38 St Paul Street, Chippenham, Wiltshire SN15 1LJ, UK: sarah.dolman@wdcs.org (2) Bahamas Marine Mammal Research Organisation, P.O. Box AB-20714, Marsh Harbour, Abaco, Bahamas (3) NOAA, Alaska Fisheries Science Center, National Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle WA 98115, USA Effective conservation requires knowledge of abundance trends. We report on an ongoing study to monitor the abundance of odontocetes in the northern Bahamas to support the newly established Bahamian Marine Mammal Protection Act, and to provide trend data for deep-divers following a mass stranding event concurrent with navy sonar (Balcomb and Claridge, 2001). Sea state influenced estimates of dwarf sperm whales, Kogia sima and Blainville s beaked whales, Mesoplodon densirostris, whilst the number of scientific observers influenced estimates of sperm whales, Physeter macrocephalus. Julian day (1 365 d) influenced dwarf sperm whale and sperm whale estimates, suggesting a seasonal effect. Estimated annual dwarf sperm whale and Blainville s beaked whale abundance decreased after 2000, whilst estimated sperm whale numbers in the study area were consistently low (Figure 2). These analyses provide the first abundance trends in this region, representing an important baseline data. Observed declines in dwarf sperm whales and Blainville s beaked whales after 2000 may be due to reductions in prey availability or the delayed impact of anthropogenic noise pollution. COMPARING RESULTS OF STOMACH CONTENT ANALYSES AND δ 13 C - δ 15 N PROFILES IN THE GALICIAN (NW SPAIN) BOTTLENOSE DOLPHIN, TURSIOPS TRUNCATUS, POPULATION Fernández, Ruth. 1 ; García-Tiscar, Susana. 2 ; Martínez-Cedeira, Jose. A. 3 ; López, Alfredo. 3 ; Palanca, Antonio. 1 ; Pierce, Graham. J. 4,5 ; Santos, M. Begoña. 5

7 1) Ecology and Animal Biology Department, Universidade de Vigo, 36200, Vigo, Spain 2) Ecology Department, Universidad Autónoma de Madrid, 28049, Madrid, Spain 3) CEMMA, Ap. 15, Gondomar, Spain 4) Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK 5) Instituto Español de Oceanografía, Cabo Estay, Canido, 36200, Vigo, Spain Bottlenose dolphins, Tursiops truncatus, are common and resident in Galician waters with an estimated population of at least 600 animals. Studies of bottlenose dolphin diet in Galicia have been carried out over the last 15 years based on stomach contents. The most important prey species was blue whiting (Micromesistius poutassou), a species of high commercial importance in Galician waters, and diet varied with body size. Because stomach contents studies represent only the dolphin s last meal, we also analysed stable isotopes profiles (carbon and nitrogen) to assess trophic level and diet composition of the species and/or animals over a longer time period. δ 13 C and δ 15 N profiles were determined from the skin and muscle of 40 stranded bottlenose dolphins between and from the tissue of 12 known dolphin prey species. Dolphins with total length between 150 and 200 cm show in their tissues (comparing skin and muscle) evidence of recent change in diet, probably due to weaning. Based on skin and muscle δ 15 N values, trophic level was, unexpectedly, found to decrease with increasing dolphin body length, which could be an indicator of social segregation and movements within the population. ESTIMATES OF MOVEMENT AND SITE FIDELITY OF NORTH ATLANTIC KILLER WHALES USING OPPORTUNISTIC INDIVIDUAL IDENTIFICATIONS Foote, Andrew D. (1) Similä, Tiu (2) Víkingsson, Gísli (3) and Stevick, Peter T. (4) (1) University of Aberdeen, School of Biological Sciences, Lighthouse Field Station, Cromarty, Ross-shire, IV11 8YJ, UK; a.d.foote@abdn.ac.uk (2) Wild Idea, Box 181, 8465 Straumsjøen, Norway(3) Marine Research Institute, Program for Whale Research, PO Box 1390, 121 Reykjavík, Iceland (4) Hebridean Whale and Dolphin Trust, 28 Main Street, Tobermory, Isle of Mull, PA75 6NU, UK Marine mammals suffer a low cost of locomotion and are known to travel large distances. Dispersal can be driven by competition with kin, temporal and spatial variation in habitat quality and prey abundance, and in-breeding avoidance. The role of dispersal in determining levels of gene flow makes it of great importance to the study of behavioural, conservation, evolutionary, and population ecology. A direct method for measuring spatial dispersal is by resighting naturally marked individuals. Multi-site mark-recapture techniques can therefore be a useful method for analysing individual movement and identifying long-range dispersal in marine mammals. Here we estimate transition probabilities of naturally marked individual killer whales between areas of high sighting density across the eastern North Atlantic and their inter-annual site fidelity within each site. Photo-identification data was collected

8 through a mixture of dedicated surveys and opportunistic encounters between from Iceland, Norway and Scotland. We find a higher probability than expected from random movement of resighting individuals between years within each study area, but limited or no probability of long-range movement of individuals between areas. We suggest that this pattern of site fidelity and low long-range emigration could be linked to the exploitation of predictable prey resources. ESTIMATING THE ABUNDANCE OF WHALES USING INFORMATION FROM SPARSE ARRAYS OF SEA-BED MOUNTED HYDROPHONES. Harris, Danielle Centre for Research into Ecological and Environmental Modelling (CREEM), University of St. Andrews. There are several benefits of using passive acoustic monitoring (PAM) to assess marine mammal populations, in comparison with visual survey methods. One type of PAM system is an array of seabed-mounted hydrophones such as the US Navy s Sound Surveillance System (SOSUS). This network of hydrophones was designed for military purposes, but can also record acoustic data from calling whales. The aim of this PhD is to develop statistical methods to produce whale abundance estimates from data recorded by SOSUS and other similar systems. The main methodology used will be based on point transect sampling, a form of distance sampling, which is commonly used to estimate bird abundance. CLIMATE CHANGE AND WHALE WATCHING TOURISM Lambert, Emily University of Aberdeen Climate change is predicted to affect the future sustainability of tourism through its influence on tourist flows. This inter-disciplinary synthesis and review presentation considers how climate change potentially threatens the sustainability of whale watching tourism. Physical, biological and biogeochemical characteristics of marine ecosystems are expected to increasingly fluctuate in response to global climate change. Such changes have implications for species of all trophic levels, including cetaceans. No research to date considers how these changes may influence whale watching tourism, which has been valued for its contribution to education, conservation and socio-economics of whale watching communities. An analytical framework is presented and used to explore how the climate change-whale watching industry relationship is balanced. Emphasis is greatly placed on a site-specific interdisciplinary approach to identifying future risks from climate change. This would initially involve integrating predictive ecological modelling of cetacean communities with a greater understanding of tourists attitudes and motivations towards whale watching and how these are influenced.

9 FUNCTION OF COMMUNICATION IN HERRING EATING KILLER WHALES (ORCINUS ORCA) Samarra, Filipa SMRU, University of St Andrews Understanding signal function, or adaptive significance, gives insight into the information used by animals and environmental constraints on signalling. Although intensively studied in terrestrial species, tests of signal function are rare in marine mammals, which limit our understanding of how communication is influenced by the marine environment. Fish-eating killer whales are well-studied, with detailed descriptions of their social structure and acoustic repertoire, though hypotheses on how sounds function are untested. This study will focus on the population of herringeating killer whales from Iceland, combining observations of call usage in different contexts and playback experiments, to provide tests of specific hypotheses on the function of calling. It will also compare the data collected from killer whales in Iceland with existing data from Norwegian herring-eating killer whales to investigate if there is sharing of call types or design characteristics. This will further enable our understanding of the importance of acoustic communication in killer whale societies. DECOMPRESSION SICKNESS IN BEAKED WHALES EXPOSED TO ACTIVE NAVAL SONAR Katie Saunders (University of Southampton) Over the past forty years, numerous mass beaching events, mostly involving beaked whales, have occurred both spatially and temporally coincident with the exposure of the whales to mid-frequency active sonar. Such events are a new phenomenon in beaked whales, and strongly contrast with the individual strandings typical of these species prior to the introduction of this sonar. Necropsies have shown that all affected individuals suffered lesions consistent with decompression sickness (DCS) a form of gas embolism new to cetaceans. My research into this phenomenon is currently focussing on how the gas emboli, (bubbles), found in the dead whales grow from pre-existing bubble nuclei. One possibility is that as nitrogen comes out of solution within the tissues during diving ascent, it moves passively into gas nuclei already present within the tissues via static diffusion. As a result, I am developing a model describing the evolution of nitrogen tensions in the tissues of diving beaked whales, which will be used to assess the probability of bubble growth in those tissues via static diffusion, and therefore the risk of the development of DCS. Several mathematical models of gas flux within odontocetes already exist, so the aim with the model I am developing is to combine the features of those models that are most relevant to the physiology of diving beaked whales to produce a model which will most precisely simulate the nitrogen fluxes within them. This species-specific model will then be used to make predictions as to the aspects of beaked whale diving

10 behaviour that put them at greatest risk of DCS. This will provide the basis for future work looking at whether particular alterations to normal beaked whale dive profiles resulting from behavioural responses to sonar put the whales at an increased risk of DCS. DISCUSSION OF SOME NEW WAYS FOR PREDICTING THE DISTRIBUTION OF MARINE ORGANISMS IN SPATIALLY COMPLEX REGIONS. Scott-Hayward, Lindesay CREEM, St Andrews University This talk will discuss the problem of how the similarity between pairs of observations is represented when determining the way in which the density of any organism varies spatially. Most algorithms use simple Euclidean inter-point similarity, which implies that points near to one another by straight line geometry are considered similar. Many marine study regions include physical barriers, such as islands, across which species do not move and so points either side of these areas should not be considered similar. Moreover, the biological distance is much greater than the simple Euclidean distance and would ideally be identified as such within smoothing methods. Improvement of these smooths, whilst retaining some degree of computational efficiency is an active area of research. There are recently several more complex smoothing methods that deal with the problem: Finite Element Splines (FELSplines) (Ramsay, 2002), Geodesic thin plate splines (Wang & Ranalli, 2007) and Laplacian thin film smooths (Wood et al. in press). These methods are compared, focussing on FELSplines in particular, using both simulated (horseshoe shape) and real data (SCANS II data for the Skagerrak and Kattegat regions of the North Sea). A knot placement algorithm (Walker & MacKenzie, 2007) for use with new and existing methods will also be discussed. ACOUSTIC PRODUCTION MECHANISMS IN PINNIPEDS Spasikova, Marija University of St Andrews The ability to develop articulate speech relies on capabilities that became available to our ancestors through changes in both peripheral mechanisms (vocal acoustics and anatomy) and neural mechanisms (vocal control and imitation). Few distantly related species (cetaceans, birds and pinnipeds) have shown the ability of vocal imitation, but of the three, only the pinnipeds use the same vocal tract as us humans. For this reason we choose to study two closely related pinniped species: the Harbour Seal (Phoca vitulina), a good vocal imitator (capable of complex vocal learning), and the Californian Sea Lion (Zalophus californicus), a close relative with very limited vocal imitation capabilities (no evidence of complex vocal learning) to look at the acoustical production mechanisms of the species as well as the neural mechanisms underlying the same.

11 Using previously acquired data gathered in California at the Long Marine Lab in collaboration with Dr.Colleen Reichmuth and Prof.Ronald Schusterman, we performed video and acoustic analysis to show correlation between jaw opening and formants frequencies in the Harbour Seal (Phoca vitulina), in speech like vocalisations. We are examining the involvement of tongue movement during these vocalisations, hypothesising that they will account for the remaining residuals in correlation between the formants excursions and jaw movements. ASSESSMENT OF THE POPULATION DYNAMICS AND CONSERVATION STATUS OF HARBOUR PORPOISE IN THE NORTH SEA USING A POPULATION MODEL TO SYNTHESIZE INFORMATION ON LIFE HISTORY, ABUNDANCE AND BYCATCH Winship, Arliss J. 1 ; Berggren, Per 2 ; Deaville, Robert 3 ; Jepson, Paul D. 3 ; Kinze, Carl C. 4 ; Larsen, Finn 5 ; Learmonth, Jennifer A. 6 ; Northridge, Simon P. 1 ; Pierce, Graham J. 6 ; Reid, Robert J. 7 ; Vinther, Morten 5 ; Hammond, Philip S. 1 (1) Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife, KY16 8LB, United Kingdom (2) Department of Zoology, Stockholm University, SE Stockholm, Sweden (3) Institute of Zoology, Zoological Society of London, London, NW1 4RY, United Kingdom (4) CCKonsult, Falkoner Alle 35 1th, DK 2000 Frederiksberg, Denmark (5) Department of Marine Fisheries, Danish Institute for Fisheries Research, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark (6) School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, United Kingdom (7) Wildlife Unit, SAC Veterinary Science Division, Drummondhill, Stratherrick Road, Inverness, IV2 4JZ, UK Bycatch of small cetaceans, such as harbour porpoise (Phocoena phocoena), in European Atlantic and North Sea fisheries is an international conservation issue. While many data are available on the life history, abundance, and bycatch of harbour porpoise in this region, these datasets have mainly been analysed separately. We developed a population model to synthesize these data with the objective of assessing the population dynamics and conservation status of harbour porpoise in the North Sea and adjacent waters. The model was fitted simultaneously to data on age at sexual maturity, pregnancy rate, age at death, abundance, and bycatch rate (per unit fishing effort) with data on total fishing effort as input. This work was an international collaboration with data contributed by several countries including the United Kingdom (UK), Denmark and Sweden. The model fitting was done in a Bayesian statistical framework using a Markov chain Monte Carlo method to explicitly account for uncertainty in parameter estimates. Results of the model fitting highlighted inconsistencies in the information provided by different datasets. Specific conclusions about population dynamics and conservation status depended on assumptions about population structure. For example, life history data from stranded harbour porpoise in the UK suggested lower birth and survival rates than were necessary to produce the observed trend in abundance when porpoises in the North Sea were treated as one population. Estimated probability distributions for model parameters were used to derive probability distributions for quantities essential to management including total bycatch mortality and natural population growth rate. These estimates of bycatch mortality and population growth rate can be used in management procedures for

12 setting appropriate limits to bycatch that have been developed for use by European governments to achieve international conservation objectives.