A computer based system for the collection of line transect survey data is described. The primary... more A computer based system for the collection of line transect survey data is described. The primary goals of the system were to measure (rather than estimate) distances and angles wherever possible, to provide accurate time-stamps for surfacing events as an aid to duplicate identification and to facilitate accurate data collection by using computers to automate data collection wherever possible. Distance and angle measurements were made using established photogrammetric techniques. Collection of photogrammetric data from video was automated and included a system of data buffering so that several seconds of data prior to each observer sighting could be captured. An additional goal of the system was to eliminate the need for post-cruise data entry and validation through the use of on-board data validation software. The system was successfully used during the 2005 SCANS-II and the 2007 CODA surveys.
Small-scale fisheries along the Swedish west coast are often operated by using small vessels, tar... more Small-scale fisheries along the Swedish west coast are often operated by using small vessels, targeting multiple species by means of pots and gillnets. Fisheries using pots targeting shellfish such as European lobster (Homarus gammarus), and edible crab (Cancer pagurus) along the Swedish west coast have a relatively high economic value. However, gillnet fisheries targeting demersal fish are currently diminishing primarily due to depleted fish stocks and increased seal depredation. Small-scale fisheries are considered sustainable fisheries due to the use of selective gears and low energy consumption. To be able to retain and promote a sustainable small-scale fishery, there is a need to develop an economically viable fishery, where selective, seal-safe and sustainable gear is utilized. One potential way forward could be to develop a pot to be used for multiple target species traditionally caught in pots and gillnets. Since both shellfish and cod (Gadus morhua) can be caught in pots, t...
Photogrammetric systems using video cameras were used to measure radial distances to sightings du... more Photogrammetric systems using video cameras were used to measure radial distances to sightings during the SCANS-II, CODA and SOWER surveys. These surveys included sightings of a variety of species from harbour porpoise, at distances of a few hundred metres, to large baleen whales at distances greater than 10km. A total of 910 initial sightings with estimated distances from reticles and measured distances from video, using 7 × 50 (636) or 25× ‘Big Eye’ (274) binoculars, were compared. Bearings to sightings were also measured from still images. The CVRMSE in distances varied between 0.19 and 0.33 for reticle binoculars. Comparisons of measured distances to simultaneous sightings by other observers using naked eye gave a CVRMSE of 0.39 for naked eye estimates. There was a consistent, non-linear pattern in all data sets, of over-estimating close distances to sightings of surfacing cetaceans and under-estimating those further away. However, this pattern was not evident from the distance ...
thanks go to both parties, to Chris Parsons at HWDT for initiating the project and to Caroline Wh... more thanks go to both parties, to Chris Parsons at HWDT for initiating the project and to Caroline Wheatley, Pauline Goodier and team, at the MOD for arranging and attending a variety of informative meetings. Many thanks go to the variety of people who assisted me in this project, from sending me relevant information in response to pleading e-mails directed all over the globe, to friends and family who looked out for, collected and delivered relevant snippets of information and knowledge. Thank you to; Grant Aitken (HOME), Sarah Dolman &
The abundance of fin whales (Balaenoptera physalus) was generated from data collected during ship... more The abundance of fin whales (Balaenoptera physalus) was generated from data collected during shipboard sightings surveys as part of the Cetacean Offshore Distribution and Abundance in the European Atlantic project (CODA). The survey area covered offshore waters beyond the continental shelf of Britain, Ireland, France and Spain. The area was stratified into four blocks and was surveyed by five ships during July 2007. Double platform methods employing the trial-configuration method (BT-method) were used. Abundance was estimated using the Mark-Recapture Line Transect design-based method and also model-based methods using density surface modelling. Estimates from the two methods were comparable but model-based methods improved the precision and were considered best estimates. The total abundance estimated for the entire survey area was 9,019 (CV=0.11) fin whales. This is likely to be underestimated because it excludes unidentified large whales, of which a large proportion were likely to have been fin whales. The uncertainty around these estimates due to duplicate classification and species identification were explored. The density of fin whales was greatest in the southern end of the survey area and water depth, temperature and distance to the 2000m contour were important predictors of their distribution. The North Atlantic Sightings Surveys have periodically covered parts of the CODA region since the 1980s but interpretation of the results is complicated by inconsistencies in survey and analytical methodologies. Only the most recent estimates from the 2007 TNASS project correct abundance estimates of fin whales for g(0). The CODA abundance estimates are the first robust estimates (corrected for responsive movement and g(0)) for this area. They are important contributions to the conservation and management of this species in the Northeast Atlanti
Marine megafauna plays an important functional role in marine ecosystems as top predators but are... more Marine megafauna plays an important functional role in marine ecosystems as top predators but are threatened by a wide range of anthropogenic activities. Bycatch, the incidental capture of non-targeted species in commercial and recreational fisheries, is of particular concern for small cetacean species, such as dolphins and porpoises. In the North-East Atlantic, common dolphin (Delphinus delphis, Linné 1758) bycatch has been increasing and associated with large numbers of animals stranding during winter on the French Atlantic seashore since at least 2017. However, uncertainties around the true magnitude of common dolphin bycatch and the fisheries involved have led to delays in the implementation of mitigation measures. Current data collection on dolphin bycatch in France is with non-dedicated observers deployed on vessels for the purpose of national fisheries sampling programmes. These data cannot be assumed representative of the whole fisheries' bycatch events. This feature mak...
Kiszka, J., Macleod, K., Van Canneyt, O., Walker, D. and Ridoux, V. 2007. Distribution, encounter... more Kiszka, J., Macleod, K., Van Canneyt, O., Walker, D. and Ridoux, V. 2007. Distribution, encounter rates, and habitat characteristics of toothed cetaceans in the Bay of Biscay and adjacent waters from platform-of-opportunity data. – ICES Journal of Marine Science, 64: 1033–1043. Data on the distribution and habitat utilization of oceanic marine mammals are difficult to collect and yet such information is beneficial for many conservation and management purposes. Data collected during ferry-based cetacean surveys in the English Channel and Bay of Biscay between 1998 and 2002 were analysed to investigate the distribution, encounter rate, and habitat characteristics of toothed cetaceans there. In all, 17 873 nautical miles were surveyed, and 1008 encounters of 13 identified species, including delphinids, ziphiids, harbour porpoise, and sperm whale, were recorded. The common dolphin was the commonest species, followed in decreasing occurrence by striped and bottlenose dolphins, pilot whal...
Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is ... more Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is one of the main causes of mortality of marine mammals worldwide. When quantitative conservation objectives and management goals are clearly defined, computer-based procedures can be used to explore likely population dynamics under different management scenarios and estimate the levels of anthropogenic removals, including bycatch, that marine mammal populations may withstand. Two control rules for setting removal limits are the Potential Biological Removal (PBR) established under the US Marine Mammal Protection Act and the Removals Limit Algorithm (RLA) inspired from the Catch Limit Algorithm (CLA) developed under the Revised Management Procedure of the International Whaling Commission. The PBR and RLA control rules were tested in a Management Strategy Evaluation (MSE) framework. A key feature of PBR and RLA is to ensure conservation objectives are met in the face of the multiple uncertai...
Sperm whales produce loud (up to 236 dB re: 1 μ Pa (rms) Møhl et al. 2003), audible, broadband re... more Sperm whales produce loud (up to 236 dB re: 1 μ Pa (rms) Møhl et al. 2003), audible, broadband regular clicks for most of the time they are engaged in deep dives. Deep dives can last for over an hour, and surface rest intervals (5-10 minutes) are typically short compared to dive times. The characteristics of sperm whale clicks makes them easy to detect and localise acoustically using relatively simple hydrophones towed behind platforms of opportunity or survey vessels (e.g. Gillespie & Leaper 1996; Leaper et al. 2000).
The objectives of the Cetacean Offshore Distribution and Abundance in the European Atlantic proje... more The objectives of the Cetacean Offshore Distribution and Abundance in the European Atlantic project (CODA) were to map summer distribution, generate unbiased abundance estimates, and investigate habitat preferences of common dolphin and other cetaceans in offshore waters of the European Atlantic. The study area was stratified into four blocks and surveyed by five ships during July 2007. Survey methods replicated those used during the SCANS-II project and the survey areas were adjacent. The survey was conducted using a ‘trial configuration ’ (‘BT mode’), with two teams of observers located on each survey vessel. This document gives results for common dolphins (Delphinus delphis). There were a total of 165 sightings of small odontocetes from the Primary platform including 104 of common dolphins, 33 of striped dolphins and 28 of common/striped dolphins (not identified to species) encountered during 9,494 km of searching effort. Abundance estimates were obtained for common and common/st...
Bycatch, the non-intentional capture or killing of non-target species in commercial or recreation... more Bycatch, the non-intentional capture or killing of non-target species in commercial or recreational fisheries, is a world wide threat to protected, endangered or threatened species (PETS) of marine megafauna. Obtaining accurate bycatch estimates of PETS is challenging: the only data available may come from non-dedicated schemes, and may not be representative of the whole fisheries effort. We investigated, with simulated data, a model-based approach for estimating PETS bycatch from non-representative samples. We leveraged recent development in the statistical analysis of surveys, namely regularized multilevel regression with post-stratification, to infer total bycatch under realistic scenarios of data sampling such as under-sampling or over-sampling when PETS bycatch risk is high. Post-stratification is a survey technique to re-align the sample with the population and addresses the problem of non-representative samples. Post-stratification requires to sub-divide a population of inter...
Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006... more Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006-2008 inclusive. The target species was Cuvier‟ s beaked whale (Ziphius cavirostris) and the aim was primarily to assess distribution and density of beaked whales ...
Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006... more Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006-2008 inclusive. The target species was Cuvier‟ s beaked whale (Ziphius cavirostris) and the aim was primarily to assess distribution and density of beaked whales ...
A computer based system for the collection of line transect survey data is described. The primary... more A computer based system for the collection of line transect survey data is described. The primary goals of the system were to measure (rather than estimate) distances and angles wherever possible, to provide accurate time-stamps for surfacing events as an aid to duplicate identification and to facilitate accurate data collection by using computers to automate data collection wherever possible. Distance and angle measurements were made using established photogrammetric techniques. Collection of photogrammetric data from video was automated and included a system of data buffering so that several seconds of data prior to each observer sighting could be captured. An additional goal of the system was to eliminate the need for post-cruise data entry and validation through the use of on-board data validation software. The system was successfully used during the 2005 SCANS-II and the 2007 CODA surveys.
Small-scale fisheries along the Swedish west coast are often operated by using small vessels, tar... more Small-scale fisheries along the Swedish west coast are often operated by using small vessels, targeting multiple species by means of pots and gillnets. Fisheries using pots targeting shellfish such as European lobster (Homarus gammarus), and edible crab (Cancer pagurus) along the Swedish west coast have a relatively high economic value. However, gillnet fisheries targeting demersal fish are currently diminishing primarily due to depleted fish stocks and increased seal depredation. Small-scale fisheries are considered sustainable fisheries due to the use of selective gears and low energy consumption. To be able to retain and promote a sustainable small-scale fishery, there is a need to develop an economically viable fishery, where selective, seal-safe and sustainable gear is utilized. One potential way forward could be to develop a pot to be used for multiple target species traditionally caught in pots and gillnets. Since both shellfish and cod (Gadus morhua) can be caught in pots, t...
Photogrammetric systems using video cameras were used to measure radial distances to sightings du... more Photogrammetric systems using video cameras were used to measure radial distances to sightings during the SCANS-II, CODA and SOWER surveys. These surveys included sightings of a variety of species from harbour porpoise, at distances of a few hundred metres, to large baleen whales at distances greater than 10km. A total of 910 initial sightings with estimated distances from reticles and measured distances from video, using 7 × 50 (636) or 25× ‘Big Eye’ (274) binoculars, were compared. Bearings to sightings were also measured from still images. The CVRMSE in distances varied between 0.19 and 0.33 for reticle binoculars. Comparisons of measured distances to simultaneous sightings by other observers using naked eye gave a CVRMSE of 0.39 for naked eye estimates. There was a consistent, non-linear pattern in all data sets, of over-estimating close distances to sightings of surfacing cetaceans and under-estimating those further away. However, this pattern was not evident from the distance ...
thanks go to both parties, to Chris Parsons at HWDT for initiating the project and to Caroline Wh... more thanks go to both parties, to Chris Parsons at HWDT for initiating the project and to Caroline Wheatley, Pauline Goodier and team, at the MOD for arranging and attending a variety of informative meetings. Many thanks go to the variety of people who assisted me in this project, from sending me relevant information in response to pleading e-mails directed all over the globe, to friends and family who looked out for, collected and delivered relevant snippets of information and knowledge. Thank you to; Grant Aitken (HOME), Sarah Dolman &
The abundance of fin whales (Balaenoptera physalus) was generated from data collected during ship... more The abundance of fin whales (Balaenoptera physalus) was generated from data collected during shipboard sightings surveys as part of the Cetacean Offshore Distribution and Abundance in the European Atlantic project (CODA). The survey area covered offshore waters beyond the continental shelf of Britain, Ireland, France and Spain. The area was stratified into four blocks and was surveyed by five ships during July 2007. Double platform methods employing the trial-configuration method (BT-method) were used. Abundance was estimated using the Mark-Recapture Line Transect design-based method and also model-based methods using density surface modelling. Estimates from the two methods were comparable but model-based methods improved the precision and were considered best estimates. The total abundance estimated for the entire survey area was 9,019 (CV=0.11) fin whales. This is likely to be underestimated because it excludes unidentified large whales, of which a large proportion were likely to have been fin whales. The uncertainty around these estimates due to duplicate classification and species identification were explored. The density of fin whales was greatest in the southern end of the survey area and water depth, temperature and distance to the 2000m contour were important predictors of their distribution. The North Atlantic Sightings Surveys have periodically covered parts of the CODA region since the 1980s but interpretation of the results is complicated by inconsistencies in survey and analytical methodologies. Only the most recent estimates from the 2007 TNASS project correct abundance estimates of fin whales for g(0). The CODA abundance estimates are the first robust estimates (corrected for responsive movement and g(0)) for this area. They are important contributions to the conservation and management of this species in the Northeast Atlanti
Marine megafauna plays an important functional role in marine ecosystems as top predators but are... more Marine megafauna plays an important functional role in marine ecosystems as top predators but are threatened by a wide range of anthropogenic activities. Bycatch, the incidental capture of non-targeted species in commercial and recreational fisheries, is of particular concern for small cetacean species, such as dolphins and porpoises. In the North-East Atlantic, common dolphin (Delphinus delphis, Linné 1758) bycatch has been increasing and associated with large numbers of animals stranding during winter on the French Atlantic seashore since at least 2017. However, uncertainties around the true magnitude of common dolphin bycatch and the fisheries involved have led to delays in the implementation of mitigation measures. Current data collection on dolphin bycatch in France is with non-dedicated observers deployed on vessels for the purpose of national fisheries sampling programmes. These data cannot be assumed representative of the whole fisheries' bycatch events. This feature mak...
Kiszka, J., Macleod, K., Van Canneyt, O., Walker, D. and Ridoux, V. 2007. Distribution, encounter... more Kiszka, J., Macleod, K., Van Canneyt, O., Walker, D. and Ridoux, V. 2007. Distribution, encounter rates, and habitat characteristics of toothed cetaceans in the Bay of Biscay and adjacent waters from platform-of-opportunity data. – ICES Journal of Marine Science, 64: 1033–1043. Data on the distribution and habitat utilization of oceanic marine mammals are difficult to collect and yet such information is beneficial for many conservation and management purposes. Data collected during ferry-based cetacean surveys in the English Channel and Bay of Biscay between 1998 and 2002 were analysed to investigate the distribution, encounter rate, and habitat characteristics of toothed cetaceans there. In all, 17 873 nautical miles were surveyed, and 1008 encounters of 13 identified species, including delphinids, ziphiids, harbour porpoise, and sperm whale, were recorded. The common dolphin was the commonest species, followed in decreasing occurrence by striped and bottlenose dolphins, pilot whal...
Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is ... more Bycatch, the undesirable and non-intentional catch of non-target species in marine fisheries, is one of the main causes of mortality of marine mammals worldwide. When quantitative conservation objectives and management goals are clearly defined, computer-based procedures can be used to explore likely population dynamics under different management scenarios and estimate the levels of anthropogenic removals, including bycatch, that marine mammal populations may withstand. Two control rules for setting removal limits are the Potential Biological Removal (PBR) established under the US Marine Mammal Protection Act and the Removals Limit Algorithm (RLA) inspired from the Catch Limit Algorithm (CLA) developed under the Revised Management Procedure of the International Whaling Commission. The PBR and RLA control rules were tested in a Management Strategy Evaluation (MSE) framework. A key feature of PBR and RLA is to ensure conservation objectives are met in the face of the multiple uncertai...
Sperm whales produce loud (up to 236 dB re: 1 μ Pa (rms) Møhl et al. 2003), audible, broadband re... more Sperm whales produce loud (up to 236 dB re: 1 μ Pa (rms) Møhl et al. 2003), audible, broadband regular clicks for most of the time they are engaged in deep dives. Deep dives can last for over an hour, and surface rest intervals (5-10 minutes) are typically short compared to dive times. The characteristics of sperm whale clicks makes them easy to detect and localise acoustically using relatively simple hydrophones towed behind platforms of opportunity or survey vessels (e.g. Gillespie & Leaper 1996; Leaper et al. 2000).
The objectives of the Cetacean Offshore Distribution and Abundance in the European Atlantic proje... more The objectives of the Cetacean Offshore Distribution and Abundance in the European Atlantic project (CODA) were to map summer distribution, generate unbiased abundance estimates, and investigate habitat preferences of common dolphin and other cetaceans in offshore waters of the European Atlantic. The study area was stratified into four blocks and surveyed by five ships during July 2007. Survey methods replicated those used during the SCANS-II project and the survey areas were adjacent. The survey was conducted using a ‘trial configuration ’ (‘BT mode’), with two teams of observers located on each survey vessel. This document gives results for common dolphins (Delphinus delphis). There were a total of 165 sightings of small odontocetes from the Primary platform including 104 of common dolphins, 33 of striped dolphins and 28 of common/striped dolphins (not identified to species) encountered during 9,494 km of searching effort. Abundance estimates were obtained for common and common/st...
Bycatch, the non-intentional capture or killing of non-target species in commercial or recreation... more Bycatch, the non-intentional capture or killing of non-target species in commercial or recreational fisheries, is a world wide threat to protected, endangered or threatened species (PETS) of marine megafauna. Obtaining accurate bycatch estimates of PETS is challenging: the only data available may come from non-dedicated schemes, and may not be representative of the whole fisheries effort. We investigated, with simulated data, a model-based approach for estimating PETS bycatch from non-representative samples. We leveraged recent development in the statistical analysis of surveys, namely regularized multilevel regression with post-stratification, to infer total bycatch under realistic scenarios of data sampling such as under-sampling or over-sampling when PETS bycatch risk is high. Post-stratification is a survey technique to re-align the sample with the population and addresses the problem of non-representative samples. Post-stratification requires to sub-divide a population of inter...
Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006... more Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006-2008 inclusive. The target species was Cuvier‟ s beaked whale (Ziphius cavirostris) and the aim was primarily to assess distribution and density of beaked whales ...
Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006... more Line transect boat-based surveys of the southern Bay of Biscay were carried out in June/July 2006-2008 inclusive. The target species was Cuvier‟ s beaked whale (Ziphius cavirostris) and the aim was primarily to assess distribution and density of beaked whales ...
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