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Environmentalists, Fishermen, Cetaceans and Fish: Is There a Balance and Can Science Help to Find it?

  • January 2002
DOI:10.1007/978-1-4615-0529-7_14
Authors:
Martin  A. Hall at Inter-American Tropical Tuna Commission
Martin  A. Hall
Greg Donovan at International Whaling Commission
Greg Donovan
  • International Whaling Commission
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Abstract

It is only relatively recently that cetologists have considered anything other than direct exploitation as an important threat to cetaceans. Given the centuries old tradition of whaling and the history of attempts to regulate the industry (e.g. see review in Donovan, 1992), this is perhaps not surprising. The issue addressed in this chapter, that of non-deliberate or incidental captures of cetaceans in fishing gear, was not seriously considered a problem until the late 1960s when biologists on board fishing vessels observed high levels of incidental catches of dolphins in the tuna purseseine fishery in the eastern tropical Pacific (Perrin, 1968). This fishery is now one of the best-studied examples (Joseph, 1994; Hall, 1998) and we will use it throughout the chapter as a case study to illustrate one approach to address a particular bycatch problem.
23. Chapter 14 Environmentalist Fishermen Cetaceans and Fi
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23. Chapter 14 Environmentalist Fishermen Cetaceans and Fi
sh.pdf
Content uploaded by Martin  A. Hall
Author content
All content in this area was uploaded by Martin  A. Hall on Jun 24, 2015
Content may be subject to copyright.
23. Chapter 14 Environmentalist Fishermen Cetaceans and Fi
sh.pdf
Content uploaded by Martin  A. Hall
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All content in this area was uploaded by Martin  A. Hall on Jun 24, 2015
Content may be subject to copyright.
... Considerable data are required in order to assess the status of a population and determine if the level of removals is sustainable Bjørge 1995, Hall andDonovan 2001). A good understanding of the stock structure and seasonal movements are required to define the area over which a population should be considered. ...
... Vinther 1999). Hall and Donovan (2001) review some of the potential biases affecting observer programs. Initiating the large scale observer programs required for many fisheries is costly and may be difficult for a number of fisheries where incidental catches occur. ...
... Determining the sustainability of direct or inci-dental removals of harbour porpoise is difficult and criteria that might be used to classify the status of populations have been the subject of great debate (e.g. see IWC 1996, Taylor et al. 1997, Hall and Donovan 2001, CEC 2002. One method of monitoring the sustainability of removals in a population is by following trends in abundance. ...
Harbour porpoise ( Phocoena phocoena ) in the North Atlantic: Abundance, removals, and sustainability of removals
Article
Full-text available
  • Jan 2014
The status of harbour porpoise (Phocoena phocoena) populations in the North Atlantic has raised numerous concerns. Although a number of factors that may be adversely affecting harbour porpoise populations have been identified, focus has been on the impact of removals, primarily due to incidental catches in fishing gear. As a result, considerable efforts have been made to determine the levels and/or impact of bycatch in a number of areas. Unfortunately, many areas remain little studied. Currently, harbour porpoise are listed as threatened or vulnerable in many parts of their range. In order to determine if the current levels of removals are sustainable, information on stock identity and seasonal movements, population parameters, abundance, and the magnitude of removals is required. Although substantial progress has been made to improve our knowledge of these parameters in the last decade, significant gaps still exist. After reviewing the available data for each sub-population in the North Atlantic, it is clear that the information required to assess the status of harbour porpoise populations is still not available for most areas. Attempts have been made to assess the status of harbour porpoise based on trends in sightings or, in areas where information on abundance and bycatch are available, on models using arbitrary criteria and/or theoretical estimates of potential population growth. Detailed case-specific population models have been proposed but are not yet available.
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... One of the key uncertainties identified during the development of the Revised Management Procedure (RMP) for baleen whales was that of uncertainty regarding stock structure (IWC, 1992;Hall and Donovan, 2001). Fig. 1 illustrates the problem generically. ...
Bayes and Empirical Bayes approaches to addressing stock structure questions using mtDNA data, with an illustrative application to North Pacific minke whales
Article
Full-text available
  • May 2023
Bayesian methods using mtDNA data are developed to compare single- and multiple-stock hypotheses. The likelihood of the data is assumed to be multinomial and the multivariate prior for the probability of an individual having a particular haplotype is assumed to be of the Dirichlet-b form. The values for the parameters of this prior are either determined using an Empirical Bayes approach or assumed to be distributed according to a log-normal hyper-prior (the ‘Full Bayes’ approach). The Empirical and Full Bayes methods are examined using simulation. The performance of the Empirical Bayes method is found to be much worse than that of the Full Bayes method. Illustrative comparisons for North Pacific minke whales based on the latter method confirm previous results that sub-areas 6 and 7 contain different stocks. Results of the application of this method to the mtDNA data for the sub-areas to the east of Japan, although generally uninformative, are nevertheless consistent with analyses based on hypothesis testing using allozymes and mtDNA. The results from this method should, however, be used for management purposes with some caution. This is because, although some testing of the Full Bayes method has been completed and suggests that when applied to data for two stocks that differ substantially in haplotype frequency, or when sample sizes are large and there is only one stock, performance is adequate, in common with most other methods for analysing genetics data, its performance has yet to be fully evaluated.
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... mean estimates of 1,000-2,400 individuals per year), in spite of a decrease in the groundfish fishing activities and total bycatches compared to the late 1980s and early 1990s. Whether current removals are sustainable for the harbour porpoise population depends on a variety of factors, including population size and rate of increase (reviewed in Donovan and Bjørge, 1995;Hall and Donovan, 2002). The abundance of harbour porpoises in the Gulf of St. Lawrence was last assessed in 1995 and 1996 using systematic line-transect aerial surveys (Kingsley and Reeves, 1998). ...
Bycatch of harbour porpoises (Phocoena phocoena) in gillnet fisheries of the Estuary and Gulf of St. Lawrence, Canada, 2000-02
Article
Full-text available
  • Mar 2023
The incidental catch of harbour porpoises (Phocoena phocoena) in the gillnet fishery of the Estuary and Gulf of St. Lawrence, Canada, was examined using: (1) questionnaires mailed to fishermen inquiring about bycatches in 2000 and 2001 (n=2,277 or 44% of the fishermen with valid licenses); and (2) using data from an at-sea observer programme and sentinel fishery programme in 2001 and 2002. The questionnaire survey had a low response rate (22%) and provided bycatch estimates of 2,215 (95% CI 1,151-3,662) and 2,394 (95% CI 1,440-3,348) porpoises in 2000 and 2001, respectively. The low number of hauls monitored by at-sea observers prevented the estimation of bycatch levels for several zones and the study area as a whole, and provided only imprecise estimates for all other zones. The results from questionnaires indicated a 24-63% reduction in harbour porpoise bycatches since the late 1980s, whereas the at-sea observer programme provided bycatch levels for 2001 and 2002 that were unreliable and underestimated, approaching one quarter of those documented in the late 1980s. Although both indices indicated a decrease in bycatches since the late 1980s, the magnitude of this change remains uncertain given the weaknesses associated with the two approaches. Considering the maximum population rate of increase (Rmax) for harbour porpoises as 4% and the lower and upper 95% confidence limits (1,440-3,348) of our most reliable estimate of bycatches (i.e. the 2001 questionnaire survey results), the harbour porpoise population in the Gulf of St. Lawrence would need to be at least 36,000-83,700 individuals for current incidental catches to be sustainable. If the rate of increase is less than maximal, e.g. 0.5Rmax or 2%, then 72,000-167,400 harbour porpoises would be needed to attain sustainability. Kingsley and Reeves (1998) estimated that an average 36,000 to 125,000 porpoises occupied the Gulf of St. Lawrence during the summers of 1995 and 1996. Although the trajectory of the population since it was last surveyed in 1996 is uncertain, these findings suggest that bycatch levels might remain a cause for concern for the harbour porpoise population in the Gulf of St. Lawrence. The results from the comparison between the sentinel fishery and the commercial fishery subjected and not subjected to at-sea observations suggest that fine-scale temporal and spatial changes in fishing activities may greatly affect harbour porpoise bycatch levels.
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... Fisheries interactions with cetaceans have been well documented in almost all existing fishing gears (Northridge and Hofman, 1999;Dalla Rosa and Secchi, 2007;Forney et al., 2011;Guinet et al., 2015) with different targeted species (Hamer et al., 2012) and at different geographical areas (Lauriano, 2004;Dıáz Loṕez, 2006;Brotons et al., 2008;Maccarrone et al., 2014;Gonzalvo et al., 2015). These interactions are associated with negative economic and conservation consequences (Hall and Donovan, 2002;Lauriano, 2006;Zollet and Read, 2006;Brotons et al., 2008), which may lead to controversial practises like culling of cetaceans to avoid depredation (Bearzi et al., 2004). The interactions between cetaceans and fisheries, can be biological or operational. ...
Understanding the Interactions Between Cetaceans and Other Megafauna With the Albacore Tuna Fishery: A Case Study From the Cyprus' Pelagic Longline Fishery
Article
Full-text available
  • May 2022
Depredation by cetaceans on fisheries is a major issue globally, both in terms of conservation and fisheries economics. The present study conducted in Cyprus, Eastern Mediterranean Sea, aimed to understand the extent, level, and type of cetacean depredation on the albacore tuna pelagic longline fishery, and in particular to quantify and evaluate the economic consequences of depredation and identify potential dolphin-longline conflict areas and mitigation practices for management. The data were obtained from fisher's logbooks, interviews and onboard observations between June and August 2018. A novel and simple approach was applied to estimate the depredation rate and economic loss by using simple calculations including the number and weight of depredated fish, landings and fishing effort. The results revealed that there is an estimated economic loss per fishing trip of 313.07± 486.19 EUR and an estimated annual economic loss for the entire fleet of 259,272 EUR from depredation caused by cetaceans. The study also estimated that 16,639 albacore tunas were depredated in 2018 and the depredation rate ranged between 0% to 100% with a mean depredation rate of 17% per fishing trip. Depredation by the common bottlenose dolphin and striped dolphin was reported in more than 50% of their fishing trips. Other species that were found to be involved in depredation were the neon flying squid, the shortfin mako shark and the Risso's dolphin. This is the first official record worldwide of depredation from the common bottlenose dolphin, the striped dolphin and the neon flying squid on the pelagic longline albacore tuna fishery. A total bycatch of 62 individuals of common bottlenose dolphins and one individual of stripped dolphin were reported in interviews as a result of depredation on bait and catch. The study also identified depredation hotspots and possible depredation mitigation measures. Such information could support the development of management action plans and measures to minimise interactions between cetaceans and pelagic longlines.
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... The discrepancies between these two studies are possibly due to the Potential Biological Removal approach being overly conservative (Hall and Donovan, 2001). The Potential Biological Removal model did not include the sex and life-stage of the bycaught individuals, and the number of dolphins killed in the fishery used in the simulations was likely overestimated (Fruet et al., 2012). ...
Dynamics and Viability of a Small, Estuarine-Resident Population of Lahille’s Bottlenose Dolphins From Southern Brazil
Article
Full-text available
  • Jan 2021
Identifying threatened populations and quantifying their vulnerability is crucial for establishing priorities for conservation and providing robust information for decision-making. Lahille’s bottlenose dolphins have been long subjected to by-catch mortality in gillnet fisheries in coastal waters of southern Brazil, particularly in the Patos Lagoon estuary (PLE) and adjacent coastal waters, where dolphins from three populations (or Management Units) show overlapping home ranges. In this study we used a stage-classified matrix population model to conduct a demographic analysis of the PLE’s population with life-history data estimated through an 8 years mark-recapture study. A population viability analysis (PVA) was used to run a series of simulations where the risk was assessed under different by-catch scenarios, taking into account the effects of parameter uncertainty and stochasticity in the projections. In the absence of by-catch, we estimated that this dolphin population would growth at a rate of about 3% annually (95% CI: 1.2–5.8%). Under current by-catch rates, prognoses indicated high probabilities of viability over the next 60 years. These optimistic prognoses appear to be associated with the high survival of adult females. However, the eventual removal of very few mature females (one every year or two) would result in a prominent likelihood of decline from its current abundance at all pre-specified levels. The viability of the population would be substantially improved if the survival of juveniles/sub-adults could be increased. This may be achieved through the recently implemented dolphin protection area, which prohibits gillnet fisheries in the core area of this population. If the protection area reduces the entanglement rates of the most impacted life-stages (i.e., juvenile/sub-adult dolphins), there would be a substantial chance of the PLE’s dolphin population increasing above 20% of its current size, which is here proposed as conservation goal. If met, this goal has the potential to promote habitat quality, increase genetic diversity and connectivity with adjacent populations, enhancing the ability of bottlenose dolphins in southern Brazil to cope with environmental change and potential disease outbreaks.
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... But the objectives of bycatch management are not so obvious when the impact on bycatch populations is sustainable) (Fauconnet and Rochet 2016). Sometimes, ethical or cultural factors may come to the forefront (Hall and Donovan 2001), adding a level of complexity to the analysis of trade-offs. ...
Mitigating bycatch in tuna fisheries
Article
Full-text available
Monitoring and managing fisheries bycatch is increasingly recognized as a critical component of robust fisheries management frameworks. This review, addressing this subject, begins by defining bycatch and analyzing the reasons it happens, from accidental to intentional discarding. It identifies the most common species composing bycatch of the main tuna fisheries using purse seine and longline gear. Considerations of options available to estimate bycatch, their potential biases and uncertainties, and ways to address these issues are discussed. The formulas used to estimate bycatch also point to the options to reduce them, lowering bycatch per unit of effort or lowering effort itself. It shows that a mean can be reduced by reducing all its component figures, or by eliminating the high values at the extreme of the distribution (i.e., where a small proportion of events causes a large proportion of the problem), a common issue in bycatch. A generic strategy is described that can be applied to all gears and fisheries, and it is then described for the fisheries of interest, showing examples of its application. These cover many mitigation actions based on gear and operational changes. Management options aiming at reducing bycatch are also mentioned. A detailed description of the ways the strategy has been implemented for purse seiners and longliners is provided. Finally, market strategies, education and awareness of stakeholders, mainly fishers, and some potential future developments are briefly described.
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... Northridge and Hofman, 1999). Such interactions generally have negative consequences for both fishery economics and the conservation status of marine mammals (Perrin et al., 1994;Hall and Donovan, 2002). Two types of interaction can be distinguished: biological and operational. ...
Interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in Asinara Island National Park (Sardinia): Assessment of catch damage and economic loss
Article
Full-text available
  • Jun 2004
In 1999, the Italian Central Institute for Applied Marine Research (ICRAM), in response to reports made by local fisheries, began a study into the interactions between common bottlenose dolphins (Tursiops truncatus) and the artisanal fishery in the Asinara Island National Park (Sardinia). Using onboard observers, fishing boat surveys were carried out to determine the frequency of interactions, variations in the catch of target species and damage to two different types of trammel net caused by dolphins. Interactions occurred primarily with trammel nets targetting striped red mullet (Mullus surmuletus; the less valuable peacock wrasse, Simphodus tinca, was also caught). Interactions also occurred with trammel nets set for lobster (Palinurus elephas), cuttlefish (Sepia spp.) and scorpionfish (Scorpaena spp.), but these were considered negligible. The target species, catch and damage inflicted on the catch was recorded, both in the presence and absence of dolphins, in an effort to ascertain associated damage and economic cost. Loss of catch was found to be significant only in the case of nets deployed during the red striped mullet fishing season. Although the level of interaction was high relative to the narrow red striped mullet fishery season, the overall economic impact on the fishing community was found to be modest. The presence and regulations of the national park area may provide an opportunity for investigating mitigation activities compatible with both cetacean conservation and the maintenance of the traditional fisheries. KEYWORDS: FISHERIES; COMMON BOTTLENOSE DOLPHIN; COMPETITION; EUROPE
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... Part of the problem with current approaches to bycatch is that our scientific understanding is still inadequate to appreciate its full ecological implications (Hall and Donovan 2002). Further research is urgently needed, especially in tropical multispecies fisheries, where the ecological impacts of bycatch have barely been studied. ...
Fishing for Answers: Making Sense of the Global Fish Crisis
Book
Full-text available
  • Jan 2004
What is the "fisheries crisis"? Are we really running out of fish? Are coastal ecosystems nearing collapse? The purpose of this report is to answer these questions and help consumers, environmental organizations, and policy-makers deepen their understanding of the issues surrounding global fisheries and find their potential roles in creating a political and economic environment that will foster sustainability in fishing.
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Exploitation and Conservation
Chapter
  • Dec 2015
The overexploitation of whales, seals, sea cows, and sea otters has resulted in seriously reduced population sizes, the extinction of several species, and the endangered status of several others. The recognition of marine mammals as crucial natural resources and valued ecosystem components that require protection has resulted in the establishment of several international legal frameworks for their conservation. Overexploitation has resulted in the extinction of three marine mammal species: Steller's sea cow, the Atlantic gray whale, and the Caribbean monk seal. Despite the establishment of legal frameworks to address exploitation, many other species have been and continue to be affected by human activities, such as bycatch in commercial fisheries, net entanglements, and environmental contaminants. Information about mortality patterns, disease, and levels of environmental contaminants has been obtained from beached and stranded marine mammals, from studies designed to address these issues in wild populations, or from laboratory tissue studies. The future of marine mammal conservation requires better information on the population status and the relationships of marine mammals with their ecosystems, as well as greater understanding of the effects of human-induced activities.
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Status of the harbour porpoise (Phocoena phocoena) in Danish waters
Article
Full-text available
  • Jan 1996
Total abundance in Danish waters is estimated as approximately 100 000 animals. Population density varies considerably by area. There are probably at least two stocks, one in the North Sea and the other in the inner Danish waters and the Baltic. The paper reviews potential threats to harour porpoise including chemical pollutants, direct exploitation, increased vessel traffic, decreased prey abundance, disease, predation and oil spills. The main threat at present seems to be the levels of bycatch in fishing gear.
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Incidental catches of dolphins in mid-water trawls for Argentine anchovy (Engraulis anchoita) off the Argentine shelf
Article
  • Apr 2000
Information on the incidental mortality of dusky and common dolphins in mid-water trawl fisheries along the Argentine shelf was obtained for the 1990s. The Argentine anchovy is believed to be an under-exploited resource and is usually taken in purse seine fisheries. However, on the few occasions when it was the target species of large mid-water trawlers, anchovy-eating dolphins were incidentally caught. A few incidents accounted for relatively high numbers of dolphins but in most of the cases the information obtained was insufficient for detailed analysis. For three cases, however, sufficient information was obtained to estimate mortality rates. Nevertheless, interpretation of these rates is difficult for a number of reasons. FV Mar Salvaje caught around 60 common dolphins (Delphinus delphis) in only a few days and in one tow 20 dolphins were caught. Biological information on 18 common dolphins (12 males and 6 females) was obtained and ages ranged from 5-10 for females and 2-18 for males.
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Incidental mortality of franciscanas in Argentine waters: the threat of small fishing camps
Article
  • Jan 1994
Artisanal fishing camps along the Buenos Aires Province are responsible for higher franciscana Pontoporia blainvillei mortality than large fishing harbours. The overall annual mortality estimate for this area is 230-250 individuals. Mortality and CPUE data suggest that higher mortality levels do not necessarily correspond to areas of higher dolphin densities. A five-year study of variation in mortality levels at one small fishing camp indicates that some difficult-to-control fishing variables (eg the preferred fishing ground of just one boat) may be the main factor in internannual mortality variation. A potential solution to the franciscana bycatch problem in a simple single target-species fishing camp is proposed and discussed. -from Author
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Estimates of incidental marine mammal bycatch in California gillnet fisheries for July through December, 1990
Article
  • Jan 1994
Four harbor porpoises Phocoena phocoena, three southern sea otters Enhydra lutris, 13 elephant seals Mirounga angustirostris, 30 harbor seals Phoca vitulina kurilensis, 67 California sea lions Zalophus californiensis, one unidentified otariid, and two unidentified pinnipeds were observed killed in the set net fisheries. Nine common dolphins Delphinus delphis, three Pacific white-sided dolphins Lagenorhynchus obliquidens, one short-finned pilot whale Globicephala macrorhynchus, one Dall's porpoise Phocoenoides dalli, one mesoplodont beaked whale, four elephant seals, one harbor seal, two California sea lions and two unidentified otariids were observed killed in the driftnet fishery. Estimated total incidental mortality is given for these species during the six month period. -from Authors
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Estimates of incidental mortality of dolphins in the eastern Pacific Ocean tuna fishery in 1994
Article
  • Jan 1996
Estimates of dolphin mortality incidental to fishing operations of the E Pacific Ocean tuna fleet in 1994 are presented. Mortality estimates were computed, using data collected by observers aboard 388 trips of tuna vessels from the international fleet. Total dolphin mortality for 1994 was 4096 animals, particularly Stenella attenuata, S. longirostris and Delphinus delphis a 14% increase in the level of incidental mortality in this fishery relative to the estimated level in 1993.
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Estimates of incidental mortality of dolphins in the eastern Pacific Ocean Tuna fishery in 1993
Article
  • Jan 1995
Total dolphin mortality for 1993 was 3601 animals, a 97% decrease in the level of incidental mortality in this fishery relative to the estimated level in 1986. Most of this decrease is attributable to improvements to dolphin safety gear and in the performance of vessel captains and crew members; between 1986-1993, the average mortality of dolphins per set decreased by 96%. -from Authors
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How many did you catch? The effect of methodology on bycatch reports obtained from fishermen
Article
  • Jan 1994
Examined the effects of method of obtaining estimates of small cetacean and seal bycatch on reports by inshore fishermen in Newfoundland and Labrador during 1990. Investigations without assessments of the methodology for obtaining bycatch reports cannot be evaluated or interpreted. Scaling corrections and improvements of survey methodology are discussed. -from Authors
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Estimates of harbour porpoise bycatch in the Gulf of Maine sink gillnet fishery, 1990-1993
Article
  • Jan 1996
Our estimates of total harbour porpoise Phocoena phocoena bycatch in the Gulf of Maine sink gillnet fishery for 1990 to 1993, with 95% confidence intervals in brackets, are 2900 (1500-5500), 2000 (1000-3800), 1200 (800-1700) and 1400 (1000-2000) respectively, rounded to the nearest 100. Because the method estimates and allows for the statistically significant undercounting in some of the observer data, the estimates are higher than previously published estimates, which did not make such an adjustment. Variance and confidence intervals are obtained by bootstrapping and possible sources of bias are discussed.
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