scholarly journals Population structure of bycaught harbour porpoise (Phocoena phocoena) in Norway

2020 ◽  
Vol 16 (3) ◽  
pp. 141-147 ◽  
Author(s):  
María Quintela ◽  
François Besnier ◽  
Bjørghild Seliussen ◽  
Kevin A. Glover ◽  
Ulf Lindstrøm
Keyword(s):  
Population Structure ◽  
Harbour Porpoise ◽  
Phocoena Phocoena

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

1991 ◽  
Vol 48 (12) ◽  
pp. 2429-2435 ◽  
Author(s):  
Thomas H. Woodley ◽  
Andrew J. Read
Keyword(s):  
Gulf Of Maine ◽  
Intrinsic Rate ◽  
Frequency Equation ◽  
Harbour Porpoise ◽  
Population Increase ◽  
Intrinsic Rate Of Increase ◽  
Natural Mortality ◽  
Phocoena Phocoena ◽  
Rate Of Increase ◽  
Incidental Mortality

We estimated the potential intrinsic rate of increase (r) of the harbour porpoise (Phocoena phocoena) population in the Bay of Fundy and Gulf of Maine using empirical data on reproductive rates (mx) and several hypothetical survival (Ix) schedules. Schedules of Ix, to maximum ages of 12 and 15 yr, were calculated from two potential natural mortality (nx) schedules combined with several schedules of incidental mortality (hx) estimates. The most realistic results were obtained when nx of non-calves were calculated from Caugley's (1966. Ecology 47: 906–918) smoothed age-frequency equation for Himalayan thar (Hemitragus jemlahicus) and applied in conjunction with a range of calf natural mortality estimates, this model indicates that harbour porpoises have a limited capacity for population increase, and populations are unlikely to sustain even moderate levels of incidental mortality (4% of the population per year). Extending the maximum age used in the models from 12 to 15 yr does little to increase estimates of r for the harbour porpoise population, and hence their susceptibility to incidental mortality.

Comparative volumes and vascular microanatomy of the intrahepatic venous system of the harbour porpoise, Phocoena phocoena (L.)

1978 ◽  
Vol 56 (11) ◽  
pp. 2292-2298 ◽  
Author(s):  
J. W. Hilton ◽  
D. E. Gaskin
Keyword(s):  
Vena Cava ◽  
Liver Weight ◽  
Harbour Porpoise ◽  
Venous System ◽  
Portal System ◽  
Hepatic Veins ◽  
Phocoena Phocoena ◽  
Diaphragmatic Muscle ◽  
Injection Techniques ◽  
Portal Veins

The intrahepatic venous systems of the harbour porpoise, Phocoena phocoena, were studied using single and double injection techniques. Large band-like formations of elastin fibres were found in the dilated terminal portions of the major hepatic veins and the adjacent section of the caudal vena cava but not in the equivalent major branches of the thicker walled portal veins. The hepatic venous system increases in volume disproportionately with increase in body length and liver weight; the portal system does not. No distal sphincter formations were found in the major hepatic veins, nor were sphincters or valves present in the portal system. The vena cava, however, is surrounded by a loop of diaphragmatic muscle or 'caval sling,' which may cause significant occlusion of the vena cava following inspiration. The distensible terminal portions of the major hepatic veins and the adjacent portion of the caudal vena cava could then function as a temporary blood reservoir or 'intrahepatic sinus.' While this would be a relatively inefficient mechanism for preventing ventricular engorgement, it might be sufficient for the needs of P. phocoena, which is a relatively poor diver.

Mitigation of harbour porpoise (Phocoena phocoena) by-catch in the gillnet fishery in the lower Bay of Fundy

1999 ◽  
Vol 56 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Edward A Trippel ◽  
Michael B Strong ◽  
John M Terhune ◽  
Jeremy D Conway
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Field Testing ◽  
Harbour Porpoise ◽  
Clupea Harengus ◽  
Bay Of Fundy ◽  
Phocoena Phocoena ◽  
By Catch ◽  
Catch Rates ◽  
Wind Sea

Demersal gill nets equipped with acoustic alarms reduced harbour porpoise (Phocoena phocoena) by-catch rates by 77% over those without alarms in the Swallowtail area of the lower Bay of Fundy during field testing in August 1996 (68% reduction) and 1997 (85% reduction) (both years combined, three harbour porpoises in 249 alarmed nets versus 14 harbour porpoises in 267 nonalarmed nets). The alarms spaced 100 m apart along the net floatline produced a 0.3-s pulse at 10-12 kHz every 4 s at a level of 133-145 dB re 1 µPa at 1 m. In conditions of no rain and low wind (Sea State 0-2) the alarms were presumed to be clearly audible to harbour porpoises at ranges of 0.1-0.6 km. Catch rates of Atlantic herring (Clupea harengus), Atlantic cod (Gadus morhua), and pollock (Pollachius virens) were not significantly different in alarmed and nonalarmed nets (except in one season when pollock were caught in lower numbers in alarmed nets). Harbour porpoise by-catch and herring movements may be linked. During years of low herring abundance, we also observed low harbour porpoise entanglement rates.

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