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WDFW
studies causes of Cherry Point herring decline
Posted
July 2001
 Summary
The
Pacific herring– a small fish that plays a huge
role in Washington's marine ecosystem– is in
trouble in some areas of Puget Sound.
Herring,
historically one of the most abundant fishes in
Puget Sound, are a staple in the diets of salmon
and many other species of fish, marine mammals and
seabirds.
The
nearshore and intertidal environment is critical
to the continued abundance of herring in Puget Sound.
Herring utilize these waters to deposit their eggs
at very specific locations– 20 distinct locations
in Puget Sound and coastal waters.
Ironically,
the spawning ground where herring were once the
most prolific– Cherry Point near Bellingham– is
now in trouble. Herring spawning rates at Cherry
Point have declined 94 percent from historic levels,
to the point that scientists now question the ability
of the stock to sustain itself.
The
reasons for the decline of Cherry Point herring
has been the focus of on-going research involving
scientists from the Washington Department of Fish
and Wildlife (WDFW) and other agencies.
By
Greg Bargman, Marine Fish Unit
WDFW Fish Program
The
stock of Pacific herring (Clupea pallasi)
which spawns in the vicinity of Cherry Point, near
Bellingham, was once the largest in Washington.
This stock has shown a dramatic decline in abundance
in recent years and is now at an unprecedented low
level.
The
decline causes concerns not only about the continued
existence of this stock, but also over the impacts
on other species of fish, marine mammals and seabirds
which feed on these fish and their spawned eggs.
Herring are one of the key links in the Puget Sound
food web. Its abundance and high energy content
make it an ideal food source for a wide variety
of animals (Table
1).
|
Table
1. Major
Predators of Pacific Herring
|
| Species |
%
of Diet Comprised of Herring |
|
Pacific
cod
|
42 |
|
Lingcod
|
71 |
|
Halibut
|
53 |
|
Chinook
salmon
|
62 |
|
Harbor
seal
|
32 |
| - Data from the
Department of Fisheries and Oceans, Canada |
On-going
WDFW research
Washington Department of Fish and Wildlife (WDFW) biologists have been studying
the stock of herring at Cherry Point since the mid-1970s. Initial efforts consisted
of monitoring the run and managing the fishery for spawning herring.
However,
since the mid-1980s, the emphasis has changed from
fishery management to resource conservation. WDFW
has re-focused its efforts to protect the herring
resource and provide a basis for stock rebuilding.
Key
research efforts now underway involve:
- Genetic
stock identification - The genetics of Pacific
herring are poorly understood. A proper understanding
of the genetics of herring stocks would be a major
benefit in protecting the resource. WDFW conducted
two separate studies of Pacific herring in 2000.
Both studies compared the genetic composition
of Cherry Point herring to that of herring from
other locations in Puget Sound and in British
Columbia. In addition, WDFW supplied herring samples
to the Department of Fisheries and Oceans in British
Columbia for a similar study of Canadian herring.
All three studies indicated that herring from
Cherry Point had genetic differences from herring
collected in other locations. However, this difference
was much less than the differences noted in salmon
collected from different spawning locations.
- Lipid
levels - Some research has investigated the lipid
(fat) abundance in adult herring. Low lipid levels
may adversely affect herring survival and reflect
a lack of food. Recent results from British Columbia
indicate that spawning herring there have low
levels of lipids. Preliminary results indicate
that herring spawning at Cherry Point have very
low levels of lipids.
- Mortality
studies - WDFW is conducting research to determine
the cause of increasing adult herring mortality.
One area of investigation is chemical contamination
of adult herring. WDFW scientists are collecting
adult herring from a variety of locations in Puget
Sound and analyzing their tissues for the presence
of a wide variety of contaminants. These contaminants
may be having sub-lethal effects on the adults,
or may be adversely affecting their reproductive
success.
 Life
cycle of herring
The Pacific herring is a species of small, schooling fish found throughout
Puget Sound and the northeast Pacific Ocean. Herring spawn at 20 well-defined
locations in Washington. The spawning grounds are very specific, as is the
time of spawning. The peak of spawning rarely varies more than seven days from
one year to the next.
Herring
spawn by depositing eggs on vegetation or other
shallow water substrate in subtidal or intertidal
habitat. The eggs are
adhesive and stick to the substrate until they hatch
10 to 12 days later (the hatching time depends on
water temperature). Following hatching, the herring
larvae drift in water currents as they feed on plankton.
Following
larval metamorphosis, the young herring spend their
first year of life in Puget Sound, although some
portion of the fish may spend their summers in the
ocean, on the west side of Vancouver Island.
When
they reach sexual maturity at two to four years
of age, the herring migrate back to their spawning
ground. Unlike salmon, herring do not all die following
spawning. Individual fish can spawn annually for
several years.
Cherry
Point stock
The Cherry Point spawning stock is one of the most important herring stocks
in Washington for two reasons. First, the stock is historically the largest
in Washington waters. Herring spawning at Cherry Point comprised about 32 percent
of the state's known total abundance. Secondly, Cherry Point herring are spring
spawning fish, in contrast to other Washington herring stocks, which are winter
spawning stocks (Table 2).
| Table
2. Major herring spawning grounds in Puget
Sound |
WINTER
SPAWNING STOCKS
(JANUARY TO MARCH) |
SPRING
SPAWNING STOCKS
(APRIL TO JUNE) |
| Squaxin
Pass |
Cherry
Point |
| Quartermaster
Harbor |
|
| Port
Orchard/Port Madison |
|
| South
Hood Canal |
|
| Quilcene
Bay |
|
| Port
Gamble |
|
| Kilisut
Harbor |
|
| Skagit
Bay |
|
| Fidalgo
Bay |
|
| Samish-Portage
Bay |
|
| NW
San Juan Islands |
|
| Interior
San Juan Island |
|
| Semiahmoo
Bay |
|
| Discovery
Bay |
|
| Dungeness
Bay |
|
 Cherry
Point herring spawning grounds extend from the north
end of Bellingham Bay north to the Canadian border
and include waters around Point Roberts and much
of Lummi Island (Fig.
2). Cherry Point is in the approximate middle
of the spawning grounds and hence gives the stock
its name. These areas also encompass a large variety
of human uses, from largely rural Lummi Island,
to residential Birch Bay, to the site of some of
the largest industrial plants in Washington at Cherry
Point itself.
While
fishery scientists have documented reports of herring
spawning in the vicinity of Cherry Point since the
1930s, little was known of their abundance until
the early 1970s.
 At
that time, interest in commercial fishing for herring
was rapidly increasing and in 1973 the first scientific
studies of herring at Cherry Point were initiated.
In 1973, the abundance was estimated to be 14,000
tons of spawning herring. Since that time, the population
has been in decline, reaching a low point of slightly
over 800 tons in 2000 (Fig.
3). This is a 94 percent decline from initial
measured abundance levels. Currently, the annual
run is well below the minimum escapement goal, which
brings into doubt the ability of the stock to sustain
itself.
The
escapement goal is the minimum amount of spawners
needed each year for the stock to sustain itself
at a level that can replace the population and provide
a harvest component. When the number of spawning
herring falls below this level, there is reason
to believe that reproductive success will be reduced.
For Cherry Point herring, the minimum escapement
goal has been calculated to be 3,200 tons. But Cherry
Point herring have not reached this level of spawning
activity for four consecutive years.
As
the stock size has decreased, spawning herring have
utilized less of their spawning grounds. The concentration
of spawning within a limited portion of the overall
habitat when the stock is small has been observed
in Atlantic herring as well. In the last few years
at Cherry Point, the spawning has been concentrated
in a few small areas (See
Cherry Point map above). Today,
only about five kilometers of the spawning grounds
are utilized. This concentration of eggs within
a small area increases the vulnerability of the
eggs to the impact of an oil spill.
|
Recruitment
is measured as the amount of herring spawning
for the first time. Herring have variable
recruitment levels. Many factors can affect
the amount of recruitment. The number of eggs
deposited is, of course, an important determinant
in the level of recruitment. However, in many
cases, the level of recruitment is not closely
related to the number of eggs deposited. Storms,
lack of food, disease and predation can strongly
influence recruitment. In Cherry Point herring,
recruitment has averaged 2,000 tons annually
and has varied widely from year to year (Fig.
6). This recruitment pattern is common
with Pacific herring in other parts of the
world. However, recruitment has been well
below average for the last four years.
The
survival rate of adult herring from one year
to the next has plummeted since the 1970s (Fig.
7). In the mid 1970s, between 70 and
80 percent of adult herring survived a year
and returned to spawn the next year. By the
late 1990s this survival rate had decreased
to 20 to 30 percent annually. This is a huge
change in the biology of herring and can explain
much of the decline in abundance.
The
decreasing survival rate of adult herring
has changed the age composition of the overall
stock. Herring spawning at Cherry Point are
getting younger. In the mid 1970s, for example,
spawning fish ranged in age from 2 to 7 years
old (Fig. 8).
By 1996, fish older than four years had become
extremely scarce in the spawning population (Fig.
9). This means that in recent years,
most of the spawning fish were comprised of
one or two age classes.
Possible
causes of decline
In general, other stocks of herring in Puget Sound have not shown a decline
in abundance similar to Cherry Point herring (Fig.
10). While stocks show considerable variation in abundance
from year to year, there is no trend comparable to that observed for
the Cherry Point herring.
Fishing
levels have been considered as a contributing
factor to the decline in Cherry Point herring.
Concurrent with increased interest in commercial
fishing for herring, a commercial fishery
at Cherry Point was authorized in 1973. During
the early years of this fishery, commercial
harvest took up to 30 percent of the run annually (Fig.
11). That high level of harvest clearly
contributed to the decline in spawning biomass
which is to be expected in unexploited populations.
However, the commercial fishery was significantly
reduced by 1981, and continued at very low
levels (<5 percent) until 1996 when it
was closed completely. The reduced fishing
opportunity was instituted by the Department
of Fish and Wildlife and tribal co-managers.
Despite the fishing curtailment and closure,
the Cherry Point stock has continued to decline.
Since there is no known harvest of these fish
in areas away from the spawning grounds, we
can conclude that while fishing contributed
to the initial decline of the stock, it has
not been a factor in nearly two decades.
|
|
Besides
human harvest, there is some thought that predation
by other fish and animals may have played a role
in the decline. Herring are fed upon by a wide variety
of other animals. The populations of at least two
of these predators, harbor seals and Pacific hake
in the Georgia Basin area, have increased substantially
since the mid-1970s and may be contributing to the
decline of herring. However, the populations of
other predators such as lingcod, Pacific cod and
chinook salmon also declined in recent years.
Environmental
factors are also believed have a significant effect
on Cherry Point herring. Because of the large amount
of industrial activity at Cherry Point associated
with refineries and other heavy industry, and the
large amount of shipping and petroleum movement
in or near the spawning grounds, it has been suggested
that contamination of the spawning grounds may be
causing or contributing to the decline. In response
to these concerns, the University of Washington
conducted studies (funded by the state Department
of Natural Resources) of developing eggs and larvae
at Cherry Point. The results of the study indicate
that:
- Newly
hatched herring at Cherry Point are smaller than
larvae hatched at other locations
- The
rate of abnormal development of larvae is high (Fig.
12)
- Eggs
deposited at Cherry Point have a low hatching
rate
Future
research
WDFW is expanding its investigation of possible chemical contamination of herring
at Cherry Point. We are collecting samples of other fish species and of crab
from Cherry Point and other locations in Puget Sound to see if other areas
and other species have similar levels of contamination. Results of these studies
are anticipated to provide a basis for evaluating the risk to herring from
contamination.
There
is a need to increase collaboration and the exchange
of information with Canadian scientists studying
herring in British Columbia. Herring in British
Columbia share a similar environment as herring
in Puget Sound and active research programs are
ongoing in both areas. WDFW is planning to host
a workshop this fall to discuss the latest findings
in herring biology and research. Scientists from
the Pacific coast and Canada will be invited to
exchange information.
In
addition, there is increasing public interest in
research findings involving Cherry Point herring.
To help meet this interest, WDFW is planning to
host a public forum on herring research this fall.
Related Reading
Alaska
Sea Grant 1991. Proceedings of the International
Herring Symposium. Alaska Sea Grant Report 91-01
Bargmann,
G. 1998. Forage Fish Management Plan. Washington
Dept. of Fish and Wildlife
EVS
Environmental Consultants 1999. Cherry Point Screening
Level Ecological Risk Assessment EVS Project No
2/868-01.0
Lemberg,
N., M. O'Toole, D. Penttila and K. Stick 1997 1996
Forage Fish Stock Status Report. Washington Department
of Fish and Wildlife Stock Status Report 98-1
Stout,
H.A., R.G. Gustafson, W.H. Lenarz, B. B. McCain,
D. M. VanDoormik, T. L. Builder and R. D. Methot
2001. Status Review of Pacific Herring in Puget
Sound, Washington. U.S. Dept. of Commerce, NOAA
Tech Memo NMFS-NWFSC-45, 175.
Related Website Links:
Washington
Forage Fish:
http://wdfw.wa.gov/fish/forage/forage.htm
Department
of Fisheries and Oceans, Canada:
http://www.pac.dfo-mpo.gc.ca/sci/herring/default.htm
StreamNet:
http://www.streamnet.org/ff/Lifehistory/herring_fact.html
University
of California Berkeley Digital Library:
http://elib.cs.berkeley.edu/kopec/tr9/html/fam-herrings.html
Author
Biography
 Greg
Bargmann is the manager of marine fish and
forage fish for the Washington Department of Fish
and Wildlife's Fish Program. Greg has worked for
WDFW for 27 years. He holds a bachelor of science
degree in biology from the University of California,
Davis and a master of science degree from the
University of Washington.
|
