Incidental mortality of harbour porpoise (Phocoena phocoena) by the gill-net fishery in the lower Bay of Fundy

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.

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Changes in Growth and Reproduction of Harbour Porpoises, Phocoena phocoena, from the Bay of Fundy

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f90-240 ◽

1990 ◽

Vol 47 (11) ◽

pp. 2158-2163 ◽

Cited By ~ 49

Author(s):

Andrew j. Read ◽

David E. Gaskin

Keyword(s):

Sexual Maturity ◽

Prey Availability ◽

Simultaneous Increase ◽

Bay Of Fundy ◽

Commercial Fisheries ◽

Phocoena Phocoena ◽

Pronounced Change ◽

Younger Age ◽

Incidental Mortality ◽

Growth And Reproduction

Changes in the growth and reproduction of harbour porpoises from the Bay of Fundy are described by comparing samples collected in 1969–73 and 1985–88. The most pronounced change was an increase in the length of calves, from 92.1 cm (SE 1.6) in 1969–73 to 108 cm (SE 1.3) in 1985–88. Females in 1985–88 attained sexual maturity at a significantly younger age (3.44 yr) and shorter length (143 cm) than females from the older sample (3.97 yr and 147 cm). These changes may be attributable to an increase in prey availability to individual porpoises. This presumed increase in prey availability may have resulted from a decrease in porpoise density caused by incidental mortality in commercial fisheries, a simultaneous increase in prey abundance, or a combination of these factors.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-162 ◽

1999 ◽

Vol 56 (1) ◽

pp. 113-123 ◽

Cited By ~ 46

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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Individual and geographical variation in pigmentation patterns of the harbour porpoise, Phocoena phocoena (L.)

Canadian Journal of Zoology ◽

10.1139/z94-017 ◽

1994 ◽

Vol 72 (1) ◽

pp. 135-143 ◽

Cited By ~ 7

Author(s):

H. N. Koopman ◽

D. E. Gaskin

Keyword(s):

British Columbia ◽

New Record ◽

Geographical Variation ◽

Individual Recognition ◽

Harbour Porpoise ◽

Bay Of Fundy ◽

Phocoena Phocoena ◽

Geographically Isolated

Photographs of 393 harbour porpoises (Phocoena phocoena (L.)) from the waters of Denmark (n = 224), Japan (n = 19), and Canada (Bay of Fundy (n = 95), Gulf of St. Lawrence (n = 40), and coast of British Columbia (n = 15)) were analyzed for variation in pigmentation patterns. Animals were classified according to morphs of each of 12 pigmentation characters. Patterns were not unique to particular areas and cannot be used as a tool for absolute discrimination among geographically isolated groups of porpoises. However, statistical frequencies of certain morphs of seven characters varied significantly among the five geographical groups, matching some of the subpopulations proposed by Gaskin in 1984. Pigmentation patterns of harbour porpoises were unique to each animal and were not gender dependent. Variation in pigmentation patterns may have implications for intra-individual recognition. All porpoises showed bilaterally asymmetrical pigmentation, providing a new record of consistent asymmetry in an odontocete species.

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Postnatal growth and allometry of harbour porpoises from the Bay of Fundy

Canadian Journal of Zoology ◽

10.1139/z97-016 ◽

1997 ◽

Vol 75 (1) ◽

pp. 122-130 ◽

Cited By ~ 39

Author(s):

Andrew J. Read ◽

Krystal A. Tolley

Keyword(s):

Growth Rates ◽

Growth Curves ◽

Postnatal Growth ◽

The Body ◽

Harbour Porpoise ◽

Body Region ◽

Bay Of Fundy ◽

Commercial Fisheries ◽

Phocoena Phocoena ◽

Thoracic Region

We described patterns of growth and allometry from observations of 203 female and 198 male harbour porpoises, Phocoena phocoena, killed in commercial fisheries in the Bay of Fundy between 1985 and 1993. Gompertz growth curves were used to predict length, mass, and girth at physical maturity. Asymptotic sizes and growth rates were greater in females for all three characters. The pattern of allometry was consistent between sexes, but varied according to body region. The characters in the head and thoracic regions exhibited negative allometry, but those in the posterior of the body were isometric. Most characters showed the same growth rates for the two sexes, except those in the thoracic region, for which females exhibited faster growth than males. These results are consistent with those of several other studies of the harbour porpoise in which faster growth and larger sizes are attained by females.

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Consumption of euphausiids by harbour porpoise (Phocoena phocoena) calves in the Bay of Fundy

Canadian Journal of Zoology ◽

10.1139/z92-225 ◽

1992 ◽

Vol 70 (8) ◽

pp. 1629-1632 ◽

Cited By ~ 19

Author(s):

Richard J. Smith ◽

Andrew J. Read

Keyword(s):

Fish Species ◽

Prey Item ◽

Stomach Contents ◽

Harbour Porpoise ◽

Bay Of Fundy ◽

Phocoena Phocoena ◽

Gill Nets ◽

Meganyctiphanes Norvegica

We compared the contents of 31 stomachs of harbour porpoise calves killed in commercial gill nets in the Bay of Fundy between July and September, 1985–1991, with the stomach contents from 149 adult animals obtained from the same source between July and September, 1988–1991. The calves' most common prey item was the euphausiid Meganyctiphanes norvegica, found in 15 stomachs, whereas the adults fed primarily on clupeid and gadid fishes. Euphausiids were also found in the stomachs of several of these fish species, and we suggest that porpoise calves take euphausiids while their mothers are feeding on other euphausiid predators.

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Harbour Porpoise (Phocoena phocoena) Presence Patterns at an Aquaculture Cage Site in the Bay of Fundy, Canada

Aquatic Mammals ◽

10.1578/am.35.2.2009.203 ◽

2009 ◽

Vol 35 (2) ◽

pp. 203-211 ◽

Cited By ~ 6

Author(s):

Marthe L. Haarr ◽

Laura D. Charlton ◽

John M. Terhune ◽

Edward A. Trippel

Keyword(s):

Harbour Porpoise ◽

Bay Of Fundy ◽

Phocoena Phocoena

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Growth of the harbour porpoise (Phocoena phocoena) in eastern Newfoundland, Canada

NAMMCO Scientific Publications ◽

10.7557/3.2748 ◽

2003 ◽

Vol 5 ◽

pp. 211

Author(s):

S F Richardson ◽

G B Stenson ◽

C Hood

Keyword(s):

Growth Rates ◽

Gulf Of Maine ◽

Harbour Porpoise ◽

Bay Of Fundy ◽

Phocoena Phocoena ◽

Growth Data ◽

West Greenland ◽

Gompertz Growth Model ◽

One Year ◽

Separate Population

Although the stock relationships among harbour porpoise (Phocoena phocoena) in the Northwest Atlantic are unknown, it has been postulated that there are 4 local populations: Bay of Fundy/Gulf of Maine, Gulf of St. Lawrence, Newfoundland, and west Greenland. Data on the Newfoundland population are extremely limited. To determine growth rates and examine if these animals can be differentiated from other sub-populations on the basis of growth characteristics, 94 porpoises caught incidentally in fishing gear along the southeast coast of Newfoundland during the summers of 1990 and 1991 were examined. Most porpoises (56%) were ≤ 4 years of age. Maximum age was 9 for females and 12 for males. Growth rates were similar for both sexes until one year of age, after which females grew longer and weighed more than males of similar ages. Using the Gompertz growth model, asymptotic values for body length were 156.3 cm for females and 142.9 cm for males. Asymptotic weights were 61.6 kg and 49.1 kg for females and males respectively. With the exception of West Greenland porpoise that were shorter and females from Norway that were lighter, Newfoundland porpoises could not be differentiated from animals collected in other areas based on growth data. However, differences in dental deposition patterns were noted suggesting that Newfoundland porpoise may belong to a separate population.

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Age at Sexual Maturity and Pregnancy Rates of Harbour Porpoises Phocoena phocoena from the Bay of Fundy

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f90-064 ◽

1990 ◽

Vol 47 (3) ◽

pp. 561-565 ◽

Cited By ~ 35

Author(s):

Andrew J. Read

Keyword(s):

Pregnancy Rate ◽

Sexual Maturity ◽

Pregnancy Rates ◽

First Year ◽

Bay Of Fundy ◽

Phocoena Phocoena ◽

Entire Sample ◽

Young Females ◽

Gill Net ◽

The Mean

Age at sexual maturity and pregnancy rate were estimated from a sample of 108 female harbour porpoises Phocoena phocoena killed incidentally in a commercial gill net fishery in the Bay of Fundy during July–September, 1985–88. Estimates of sexual maturity ranged from 3.15 to 3.44 yr, depending on the method used; few individuals older than 7 yr of age were present in the sample. The mean age at first pregnancy was 3.76 yr. Pregnancy rate was estimated using two methods: (1) considering the entire sample and using the presence of a corpus luteum as indicative of pregnancy, and (2) by considering the sample collected after implantation and using the presence of a foetus as the criterion of pregnancy. Estimated pregnancy rates using these two methods were 0.86 and 0.74, respectively. Many young females failed to conceive in their first year or two of sexual maturity, but most older females in the sample were pregnant. These high pregnancy rates are indicative of annual reproduction in this population.

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Observations on the ventilation cycle of the harbour porpoise Phocoena phocoena (L.) in coastal waters of the Bay of Fundy

Canadian Journal of Zoology ◽

10.1139/z83-015 ◽

1983 ◽

Vol 61 (1) ◽

pp. 126-132 ◽

Cited By ~ 16

Author(s):

A. P. Watson ◽

D. E. Gaskin

Keyword(s):

Coastal Waters ◽

Marine Mammals ◽

Average Duration ◽

Extended Period ◽

Harbour Porpoise ◽

Orcinus Orca ◽

Behaviour Pattern ◽

Bay Of Fundy ◽

Phocoena Phocoena ◽

Observation Period

The ventilation cycle of the harbour porpoise was studied through analysis of 700 dive sequences recorded in the Fish Harbour region of southern New Brunswick. Two basic ventilation patterns were recognized; one (pattern A) was exhibited by travelling animals and was characterized by short submergence periods (24.4 ± 1.6 s (SE)), the second (pattern B) by animals apparently feeding, and was characterized by restricted ventilation periods, between which the submergence periods averaged 1.44 ± 0.07 min. Submergences during pattern B behaviour ranged from 35 s to 4 min 4 s. One animal observed over an extended period took considerably more breaths (6.6 ± 0.4) after dives of above-average duration than after dives of less than average duration (3.6 ± 0.2). We found that the number of breaths per minute in each behaviour pattern were very similar (2.4 and 2.3, respectively), supporting statements by other workers that the energetic demands of diving in marine mammals may not be greater than that required for surface activity. In behaviour patterns A and B, respectively, harbour porpoises in this area were at the surface for only 7.2 and 7.5% of any observation period. The maximum to mean dive-time ratio in P. phocoena was noted as being almost identical to that observed in Orcinus orca; this may be a generalized relationship in all odontocetes.

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