- Volume 2, Issue 1, Summer 2000 -
Summary of harbour porpoises in weirs
Data collected from porpoises in 2000
Health of the local porpoise population
Improving our methods for release
Our new Boat
Proposed work for next year
During the winter…
We would like to thank everyone for participating in the harbour porpoise release program this year. Last year we initiated an annual Weir Release Newsletter, describing our activities for the summer. This is the second issue of the newsletter, in which we hope to let you know a little bit about the work we conducted this season.
There were relatively few porpoise entrapments in Grand Manan herring weirs during the 2000 season. We recorded only 17 porpoises in weirs, making this the quietest year for porpoises since 1996 (a year when there were only 6 porpoises in local weirs). For comparison, last year we observed 76 porpoises in weirs, and we were able to help you release 94% of them successfully.
This year, we helped you seine out 13 of the 17 recorded entrapped porpoises. Of the remaining 4, 2 swam out on their own and 2 we are uncertain of. The 17 porpoises showed up in only 6 weirs, a pattern we observed last year as well. This year was also the first season in which we didn’t see a single porpoise in a Whale Cove weir. We did release 4 porpoises from a weir on White Head Island, where we haven’t spent much time in the past.
In addition to being a quiet year for porpoises, it was also a late year. We didn’t record the first porpoise in a weir until August 8, which was a month later than our first porpoise in 1999. All porpoise entrapments were concentrated within a two-week period from August 8th to the 23rd.
There was one minke whale that we know of this year, and it was seined out with the mammal seine on July 5th.
Of the 13 porpoises we released, we were able to collect sex and body size data for 12. We know that we released 8 females and 4 males. Most of the porpoises we released were juveniles (1-3 years old), and only one of them was an adult: a female with her calf. This mother/calf pair represented the smallest (calf was 113 cm long) and largest (the mother was 157 cm long and weighed 61 kg) porpoises of the season. Typically we see a few mature males in weirs each summer, but none of the males we released this year were large enough to be adults.
As part of a long-term study monitoring the general health of this porpoise population, we collected blood samples from 7 individuals. These blood samples undergo two types of analyses. First, part of the blood is sent immediately to St. John, where the different types of blood cells are counted and levels of oxygen-carrying hemoglobin are measured. Later each fall the remainder of the blood, which is frozen, will be sent to the Ontario Veterinary College in Guelph, Ontario for chemistry analyses (enzyme activities, levels of different salts, proteins, and hormones, etc.). From these data we are starting to build a baseline picture of the blood values of the average wild porpoise, and we have collected enough samples to know when the values from a particular porpoise are unusual. From the data we have obtained so far (samples from over 100 porpoises since 1993) it appears that the porpoises around Grand Manan are generally in good health, with little evidence of infections or other diseases.
One of our goals is to improve our methods of release so that the process is easier for everyone (fishermen, researchers and porpoises!). One way to greatly increase our chances of releasing porpoises alive is to seine them out with the mammal seine (the seine made of dragger twine, also known as the “predator net”). This summer saw an increase in the use of the mammal seine (5 out of the 7 seines for porpoises) compared to previous years. We had always thought that use of the mammal seine resulted in a greater number of successful releases, but didn’t know until this year exactly how effective this net is. We have now analysed the past 9 years of seining data and in that time we have never had a porpoise die when seining with the mammal seine. Porpoise mortality is likely reduced because the seine is lighter, it is easier for the porpoises to see, and there are no herring present to confuse the porpoises. We are very pleased with the performance of this net and would like to encourage its use whenever possible in the future.
Each year we also try to reduce the amount of stress porpoises undergo during the release process. For the past few years we have been videotaping every seine so that we can monitor the behaviour of animals in the water and in the boat. We use these tapes to evaluate our performance, as well as each porpoise’s breathing rates and reactions. We also monitor their heart rates (another indicator of stress) with a monitor that is used by training athletes. This study will be long-term and we hope to be able to use the data to help us reduce the porpoises' stress levels by modifying the way we interact with and handle the animals while they are in the boat.
This year we were able
to deploy satellite tags on two porpoises. When these tags are at the surface
(i.e. when the porpoise breathes) they 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 about 6 months.
We are unable to track the animals for longer periods because we are limited
by battery life: larger batteries for longer tracks would make the
tags too big for porpoises. We had originally intended to deploy
more tags but because most of the porpoises we handled this year were fairly
young, they were too small for tag attachment. The porpoises we put
electronic tags on are listed in the table below (we name each one).
Those of you with internet access can track the movements of these porpoises via the Web. Wheelock College in Massachusetts received a grant to create an educational web page about science for use in classrooms. The idea behind this is that young students will become more interested in science if they can see real data right in front of them. With their grant money, 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 site: http://whale.wheelock.edu/whalenet-stuff/StopPp2000/
We plan to continue the Harbour Porpoise Release Program next year, assisting you with the safe release of porpoises from your weirs. As most of you already know, the Harbour Porpoise Release Program is funded entirely through donations and grants from conservation organizations. We receive no government support. The majority of the electronic tags we deploy on porpoises have been donated to us by Whalenet, as we are only able to purchase one or two tags per year with our grant money. Each year we have to reapply to four or five organizations in order to raise enough funds to run the program for the summer.
We are currently working on a project called Weir Outreach which was funded by the Fundy Community Foundation. This project will create a guide that will describe the porpoise release techniques that we have developed with the help of Grand Manan fishermen over the past 10 years. This manual will be circulated to all weir fishermen in New Brunswick and Nova Scotia and will hopefully serve as a guide to help weir fishermen outside Grand Manan release porpoises from their weirs.
We also 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. Please feel free to drop by the Research Station any time during the summer if you have questions, comments or suggestions.
Though Laurie lives here 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). Several of us now spend the winter in Beaufort, North Carolina, where we go to school at the Duke University Marine Laboratory. If you ever head south during the winter, be sure to drop by.
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
Harbour Porpoise Release Program - home page