- Volume 3, Issue 1, Fall 2001 -
Summary of porpoises in weirs
2001 Weir Awards
Health of porpoise populations
Porpoises on the web
An unusual release...
Support for the HPRP
Plans for next year
During the winter...
This has been a banner year for the Harbour Porpoise Release Program. As all of you are aware, the summer of 2001 presented us with more porpoises in weirs than anyone could recall seeing before. We would like to thank all of you for participating in the HPRP again this year, and for being so cooperative throughout our long summer of porpoises!
This year, we recorded 310 porpoises in weirs around Grand Manan, plus an additional pair of porpoises in a weir on Campobello. Of these 312, 51 swam out on their own and 244 were released. Fourteen porpoises died while we were attempting to seine them out, and the fates of the last three are unknown. Regardless, all of us should be proud of the 2001 porpoise release program: 244/258 gives us an overall live release rate of 94.6%. In a year with so many porpoises, this is extremely successful.
These unprecedented entrapment rates, resulted in an extremely busy year: we seined with you a total of 102 times, from July 9 to September 21, and it was not unusual for us to seine 4-6 times in a single day (the snorkelers began to feel as though they were living in their drysuits!). The mammal (predator) seine was used very frequently in 2001, accounting for more than 2/3 of the seines we attended. Demand for this seine was high, often with two or three of you needing to use it on a tide; we are hoping to be able to construct a second mammal seine for use next year to meet this need (see below).
This summer we more than doubled our previous live release record of 113 porpoises back in 1993. Recent release totals have been much lower: 13 in 2000, 48 in 1999, and 12 in 1998. Each year our success rate hovers around 94%, so we are pleased that we were able to maintain that success rate with so many porpoises around this year.
Usually we can detect some trends in porpoise entrapments throughout the summer, associated with tide/moon phase or cloud cover. This year, porpoises swam into weirs almost every night from July 19 to September 16, regardless of environmental conditions. One thing we did notice on many occasions this year was a “multiplying effect”: if there were one or two porpoises in a weir one day, there would often be five or six (or thirteen!) in it the next day.
In addition to the porpoises, four minke whales were released from Grand Manan weirs using the mammal seine. Although there were many more porpoises in weirs this year, the number of minke whales did not show any increase over previous years, suggesting that the factors influencing weir entrapment may be different for these two species.
Of the 244 porpoises we released, we were able to gather some data from 214 of them. We had almost twice as many males (137) as we did females (77). We measured the standard lengths (from the tip of the rostrum [“nose”] to the notch in the flukes) on 122 males and 70 females. Porpoise of all sizes and ages swam into weirs this summer: adult males and females, juveniles and even calves were released. We clipped small, uniquely numbered plastic roto-tags (used on sheep and pigs) on the dorsal fins of the 214 porpoises (red for females and yellow for males—we change colours every year); these tags allow us to identify individuals if they are later resighted…and they were (see below)! We released the other 30 individuals (many of these were swept out, rather than seined) without recording their genders or measuring their sizes, or fitting them with rototags.
Although we have been putting out rototags on porpoises for the past 15 years, we usually don’t see many of the rototagged animals after they’ve been released. This year, however, we had 18 repeat visitors who were already fitted with rototags. Interestingly enough, though, porpoises that were already rototagged would always be with a new group of non-rototagged animals. This suggests to us that the relationships between individual porpoises might not be as close or tightly organised as those of other species of toothed whales, such as killer whales and bottlenose dolphins.
The majority of our repeat visitors were tagged in 2001, but we did have five porpoises return from previous years…one as far back as 1992! This animal was particularly interesting, as he was already an adult in 1992 when we released him from First Venture. The average lifespan of a harbour porpoise is 10-15 years, and they become sexually mature at age 4. Thus our 1992 returnee would have been at least 13 years old when we released him from Eagle Rock this year, making him fairly old for a porpoise! Three of the rototagged porpoises were caught more than twice, suggesting that the seining and release experiences certainly don’t deter all animals from swimming back into another weir.
Given the high number of
porpoise entrapments and releases this year, we thought it would be fun
to announce some “2001 Release Program Weir Awards.”
We collected blood samples from 57 of the porpoises we released as part of a long-term study aimed at monitoring the health of the local porpoise population. These blood samples are sent to the Saint John Regional Hospital for counts of red and white blood cells, and to the Ontario Veterinary College in Guelph for analysis of enzymes and chemistry. Preliminary analysis of the blood indicates that porpoises around Grand Manan are generally in good health. This year we did notice a few porpoises with small ulcerations on their skin, and three animals with parasitic copepods (sea lice) on them. Analysis of blood hormone levels also allows us to determine whether females are pregnant. All 8 females that were large enough to be adults showed signs of being pregnant, based on progesterone levels. This is not surprising, as we would expect most or all female porpoises in this population to be simultaneously pregnant and nursing a calf each year.
This year we deployed satellite
tags on four male porpoises. When these porpoises are at the surface (i.e.
when they surface to breathe) the tags transmit information to orbiting
satellites, allowing the position of the animal to be calculated. These
data are then transmitted to a ground station and we are able to access
the positions via computer downloads. These tags allow us to remotely track
the movements of porpoises for between 6 months and a year. We are unable
to track the animals for longer periods because the tags have limited battery
life: larger batteries for longer tracks would make the tags too big for
porpoises. The porpoises fitted with electronic tags are listed in the
following table (we name each one).
Those of you with internet
access can track the movements of these porpoises via the Web, on a website
designed for public schools by Wheelock College in Massachusetts. It is
hoped that young students will become more interested in science if they
can see real-world data as scientists collect it. Wheelock College donates
electronic tags to us and to other researchers. In exchange, we provide
them with the data we collect so it can be used on their web page, called
Whalenet. You can check out the travel paths of the porpoises listed above
by going to this web address: http://whale.wheelock.edu/whalenet-stuff/stop_cover.html
To our surprise, we added a new species to the Release Program this year. The morning of September 6 found us rescuing a female ruby-throated hummingbird from the twine of DoLittle (Atlas). Once we fed her sugar water and she warmed up in the sun, she preened herself and then flew away with another hummingbird that had ventured into our backyard.
The Harbour Porpoise Release Program was funded by a wide variety of sources this year, and we need to thank all of them for helping us make it through the summer. Because of the high numbers of releases in 2001, we faced considerable financial challenges, keeping up with both the logistical costs of running the program and our seining costs. We received initial support for the Release Program from the International Fund for Animal Welfare, Whale and Dolphin Conservation Society, Connors’ Brothers, and donations from individuals to the Research Station. By the end of July, however, funds from these sources were completely exhausted. Fortunately we were able to secure emergency funding from the International Fund for Animal Welfare, as well as support from the United States Marine Mammal Commission, the Humane Society of the United States, and the New England Aquarium. Funds and support provided by these organizations and individuals were of critical importance to the success of the Release Program this summer, and we owe them all a sincere thank you for their help.
Such a positive working relationship between fishermen and scientists is unusual, not only in Canada but in a global sense, and we thank you for helping us build a strong partnership with you.
Given our surprise at the unprecedented number of porpoises in weirs this year, we have no way of predicting what next summer will bring. Nonetheless, we will continue the Harbour Porpoise Release Program next year, assisting you with the safe release of porpoises from your weirs.
Fairly early on in the summer, it became obvious to us (and to you!) that one mammal / predator seine was insufficient to meet everyone’s seining needs, whether they be for porpoises, whales, or other marine species. Often, several of you would need to use the seine on the same tide, or would be forced to “reserve” it several days in advance. Because of this, plans are underway (pending funding under an initiative headed by the GMFA) to construct a second seine over the winter. Hopefully this will alleviate some of the congestion associated with the existing mammal seine, and make seining more efficient next year.
We do conduct other scientific work during the summer, focusing on the behaviour and physiology of porpoises and seabirds, and how these animals use and interact with their environments (although this year much of our research time was spent seining!). Please feel free to drop by the Research Station any time to ask us what we’re doing.
We would like to thank all of you for making the Harbour Porpoise Release Pro-gram a success each year. This has been a very busy and active summer for the Harbour Porpoise Release Program, and our impressive rate of live releases is due largely to the support and cooperation of all of you who own, tend, and seine herring weirs. We should all be proud of what the Release Program has evolved into over the past 10 years: since 1991 we have released over 630 porpoises from weirs in the Bay of Fundy. What we have accomplished together, particularly this year, demonstrates a high level of commitment on the part of the weir industry to maintain an environmentally friendly, sustainable fishery.
Though Laurie, the Research Station managing director, lives on Grand Manan all year, the rest of us scatter to different places during the winter. If you have any questions, suggestions, or comments, we can all be reached through the Research Station (email: firstname.lastname@example.org). Some of us will head back to Ontario, and several of us will spend the winter at the Duke University Marine Laboratory in Beaufort, North Carolina (at the bottom of the Outer Banks), or at Woods Hole Oceanographic Institution (on the south-west corner of Cape Cod). If you ever head south during the winter, be sure to drop by! Hopefully you’ve all received our recently published porpoise release guidelines and the waterproof wheelhouse card; if not please contact us for free copies of both.
Please feel free to contact us any time, if you have questions, or suggestions, or want to see us about something interesting you have seen. You can reach us through the Research Station.
the Grand Manan Whale and Seabird Research Station Research Station
About the Gaskin Fellow Program
The Gaskin Fellow Program was initiated by the GMWSRS in 2000, in honour of Dr. David Gaskin and his contributions to conservation and science in the Bay of Fundy. The program provides summer employment for a local high school student conducting research on marine mammals in the Bay of Fundy.
A GOOD WINTER AND WE'LL SEE YOU NEXT SUMMER!
Harbour Porpoise Research: 1997 | 1998
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