Sea Grant Project Progress Report
| Updated
13 September 2002 |
| Project Title: |
The Seasonal and Biochemical Nutritional
Variance in Pollock as a Food for Marine Mammals |
| Project Number: |
R/101-03 |
Initiation Date: |
02/01/2002 |
| Revision Date: |
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Completion Date: |
01/31/2004 |
| Principal Investigator: |
Michael
Castellini |
| Affiliation: |
Institute of Marine Science, School of Fisheries
and Ocean Sciences, UAF |
| Sea Grant Funds: |
$101,955 |
| Match Funds: |
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| Related Projects: |
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| Parent Projects: |
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| Keywords: |
pollock, marine mammals, nutrition, seals,
sea lions, proximate analysis |
| 1. Objectives: |
This project has one major goal: To quantify
the nutritional variance in pollock over seasonal and developmental
time frames in the context of known seasonal alterations in pinniped
nutritional physiology. |
| 2. Rationale: |
Based on our recently completed feeding
trials with harbor seals (Phoca vitulina) at the Alaska
SeaLife Center (ASLC), it is clear that there are significant
seasonal differences in how pinnipeds respond to controlled diets
of herring (Clupea harengus pallasi) versus pollock (Theragra
chalcogramma). That is, at some times of the year, seals gained
fat and body mass on both herring and pollock. At other times
of the year, they lost body fat on both species, but gained mass.
In these trials, the seals were fed from single batches of fish
during the two-year experiment. Thus, fish quality was held as
a constant. In nature, however, the body composition of fish is
not constant and presumably varies seasonally and developmentally
in nutritional value to the seals.
A similar three-year seasonal and dietary regime feeding study
with Steller sea lions (Eumetopias jubatus) at the ASLC
is not yet finished, but also shows clear seasonal variation in
how the seal lions respond to a constant diet. Based upon our
work with seasonal dietary manipulation, the next logical step
in this process is to understand how season impacts the nutritional
value of the fish. Therefore, this Sea Grant project is to quantify
the seasonal nutritional and biochemical differences in fish and
relate how those differences co-vary with measured changes in
pinniped metabolism. Because pollock is a significant fishery
in Alaska and because it is a focal point of current predator-prey
studies with marine mammals, this Sea Grant project is limited
to that species. |
3. Benefits:
|
The scientific and management impact of this
work is that we will provide seasonal data that can be used in optimal
foraging or strategic habitat models for predator-prey relationships
between marine mammals and pollock. Current models assume that prey
quality is constant throughout the year and that pinniped metabolism
does not change seasonally; both of these assumptions are most likely
not correct. While this proposal does not develop those optimal
foraging strategies or habitat models, it can provide data to managers
and researchers who need this information for model development. |
| 4. Accomplishments: |
September 2002
- We have formed a collaboration with Dr. Bob Foy and his project
to collect fish from around the Kodiak vicinity. Susan Inglis
participated in a research cruise with Dr. Foy in July, 2002.
- We have collected prey (pollock) samples for Dec./Jan., March,
May, and July from the Kodiak area. Samples will be collected
in November of this year as well.
- We have collected samples from three age classes of pollock
in July from the Kodiak area.
- We have collected prey samples for August from the Chiswell
Island area including three age classes of pollock.
- Sample preparation and analysis has begun.
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| 5. Students Supported: |
Susan Inglis. Ph.D. Marine Biology, University
of Alaska Fairbanks. |
| 6. Extras and Follow-up: |
We are on schedule for both the field and
laboratory work. It is noteworthy that collaborations are being
set up with other agencies, investigators, and projects in order
to accomplish this work. |
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