Potential Rates of Increase of a Harbour Porpoise (<i>Phocoena phocoena</i>) Population Subjected to Incidental Mortality in Commercial Fisheries

Woodley, Thomas H.; Read, Andrew J.

doi:10.1139/f91-284

Cited by 50 publications

(48 citation statements)

References 8 publications

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“…and Pacific herring net fisheries operate. Certainly, bycatch has been shown to be a significant source of porpoise mortality in other geographic areas (Gaskin, 1984;Read and Gaskin, 1988;Woodley and Read, 1991;Read et al, 1993) and may, in fact, be responsible for the downward trend observed in our data for the mid-2000s. We are unable, however, to attribute the decline in the mid-2000s to incidental takes in the net fisheries given that interaction data are not available.…”

Section: Figurementioning

confidence: 65%

Temporal changes in abundance of harbor porpoise (Phocoena phocoena) inhabiting the inland waters of Southeast Alaska

Dahlheim

Zerbini²,

Waite³

et al. 2015

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Abstract-Abundance of harbor porpoise (Phocoena phocoena) was estimated from data collected during vessel surveys conducted throughout the inland waters of Southeast Alaska. Line-transect methods were used during 18 seasonal surveys spanning 22 years . Estimates were derived from summer surveys only because of the broader spatial coverage and greater number of surveys during this season than during other seasons. Porpoise abundance varied when different periods were compared (i.e

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Section: Figurementioning

confidence: 65%

Temporal changes in abundance of harbor porpoise (Phocoena phocoena) inhabiting the inland waters of Southeast Alaska

Dahlheim

Zerbini²,

Waite³

et al. 2015

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“…Woodley and Read (1991) estimated that the maximum rate of increase of otherwise unstressed populations of small cetaceans was around 4% but the IWC have adopted a ®gure of 1% of estimated abundance above which has expressed concern over the sustainability of anthropogenic removals (Anon, 1996). Obviously the reported by-catch in this study does not come near to this level of removal but further observer studies will have to be carried out before catch rates can be con®dently extrapolated to wholē eets and ®sheries and before the potential impact of incidental capture in pelagic and other trawl ®sheries fully assessed.…”

Section: Biological Significance Of Marine Mammal Bycatchesmentioning

confidence: 99%

Incidental catches of marine-mammals in pelagic trawl fisheries of the northeast Atlantic

Morizur

Berrow

Tregenza³

et al. 1999

Fisheries Research

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Marine mammal by-catch in 11 pelagic trawl ®sheries operated by four different countries in the northeast Atlantic was studied. Observers accompanied commercial ®shing vessels and monitored 374 tows totalling 1771 h of towing during 377 days ®shing. Three species of marine mammal were identi®ed in by-catches (white-sided dolphin, Lagenorhynchus acutus, common dolphin, Delphinus delphis and grey seal Halichoerus grypus) and a fourth, bottlenose dolphin Tursiops truncatus, was probably present. Dolphins were caught in four of the 11 ®sheries and seal in one. In those ®sheries with cetacean bycatch, rates varied from 0.0606 to 0.1000 per tow and 0.0107 to 0.0137 per hour of towing and were highest in the French sea bass ®shery and lowest in the French tuna ®shery. Grey seals were caught in the Irish Celtic Sea herring ®shery at a rate of 0.0513 per tow or 0.0396 per hour of towing. The mean AESD dolphin catch rate for all ®sheries combined was 0.048AE0.013 per tow (one dolphin per 20.7 tows), or 0.0185AE0.0019 per hour of towing (one dolphin per 98 h of towing) and, for all marine mammals, 0.059AE0.019 (1 per 17.0 tows) or 0.0124AE0.0121 (1 per 80.6 h of towing). 95% con®dence intervals, calculated on untransformed data, for all ®sheries combined were 0.4±1.6 dolphins per 100 h of towing.No operational factors were correlated with by-catch rates but the haul-back procedure was identi®ed as a potentially important factor. All dolphin by-catches occurred during the night which may be a due to an association between cetaceans and trawlers at night. White-sided dolphins and grey seals were observed feeding around the net during towing and this behaviour may make them more vulnerable to capture. Operational dif®culties in observing by-catch and potentially signi®cant annual¯uctuation in catch rates warrant further observer studies of these and other trawl ®sheries. #

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“…Recent estimates of the numbers of harbour porpoises killed in Canadian and American commercial fishing operations (Lien 1987, Fontaine et al 1994a, Bravington & Bisack 1996, Trippel et al 1996, together with the limited potential of the species to withstand such mortality (Woodley & Read 1991) have raised concern over the status of this species in the North Atlantic. For example, the Committee on the Status of Endangered Wildlife in Canada considers western Atlantic harbour porpoises as threatened (Gaskin 1992).…”

Section: Introductionmentioning

confidence: 99%

Geographical differences in organochlorine contaminants in harbour porpoises Phocoena phocoena from the western North Atlantic

Westgate¹,

Tolley²

1999

Mar. Ecol. Prog. Ser.

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Organochlorine contaminants, includng polychlorinated biphenyls (PCBs), chlorinated bornanes (CHBs), dichloro-diphenyl-trichloroethanes (DDTs), chlordanes (CHLORs), hexachlorocyclohexanes (HCHs) and, chlorobenzenes (CBZs) were quantified in 188 harbour porpoises (Phocoenaphocoena) killed in commercial fisheries in the coastal waters of the Avalon Peninsula, Newfoundland (n = 29), the Gaspe Peninsula, Quebec (Gulf of St. Lawrence) (n = 58), Grand Manan Island, New Brunswick (Bay of Fundy) (n = 86), and Jeffreys Ledge in the Gulf of Maine (n = 15). Levels were compared to determine if there were systematic differences in the organochlorine (OC) contaminant composition of harbour porpoises from these areas (Newfoundland, St. Lawrence, Bay of Fundy-Gulf of Maine) in the western North Atlantic. Bivariate analyses run on all 188 individuals showed both Fundy-Maine and St. Lawrence males had significantly hlgher levels of CHLORs, DDTs, PCBs and CHBs than Newfoundland males. Fundy-Maine males also had significantly higher levels of CHLORs and PCBs than those from the St. Lawrence and St. Lawrence males had significantly higher levels of HCHs than males from Fundy-Maine. Females from Fundy-Maine had significantly higher levels of total PCB than both St. Lawrence and Newfoundland females. Total DDT levels were significantly h g h e r in FundyMaine and St. Lawrence females than those from Newfoundland. Total CHLOR values were sigmficantly hlgher in Fundy-Maine than in Newfoundland females. Multivariate analysis, run on a subset consisting of 100 immature harbour porpoises showed significant differences among the group centroids on both discriminant functions (Wilks' Lambda; p c 0.001) demonstrating that these geographic groups are distinguishable based on OC levels. These results indicate that delineating the western North Atlantic harbour porpoise population into sub-populations defined as Newfoundland, Gulf of St. Lawrence and Bay of Fundy-Gulf of Maine is appropriate.

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Potential Rates of Increase of a Harbour Porpoise (Phocoena phocoena) Population Subjected to Incidental Mortality in Commercial Fisheries

Cited by 50 publications

References 8 publications

Temporal changes in abundance of harbor porpoise (Phocoena phocoena) inhabiting the inland waters of Southeast Alaska

Temporal changes in abundance of harbor porpoise (Phocoena phocoena) inhabiting the inland waters of Southeast Alaska

Incidental catches of marine-mammals in pelagic trawl fisheries of the northeast Atlantic

Geographical differences in organochlorine contaminants in harbour porpoises Phocoena phocoena from the western North Atlantic

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