Striped Bass
Striped Bass
Background
Coos River Basin Fish Management Plan 1990
Striped Bass up to 35 lbs are not unknown in the Coquille River
Striped bass, which are native to the Atlantic and Gulf coasts of the United States, were first introduced in the Pacific Coast in the late 1800s when 432 yearling fish where released into San Fransico Bay. The first striped bass appeared in Coos Bay in 1914 when two adult fish were caught in a gill net by Alfred Justrum, a commercial fisherman. Since 1914, reproducing populations of striped bass have become established in the Coos, Coquille, Uppqua, Smith, and Siuslaw estuaries. Striped bass have been found in the Columbia River and as far north as Barkley Sound, British Columbia.
The Striped bass population in Coos Bay expanded rapidly after 1914, and by the mid-1920s a commercial fishery had become established and a recreational fishery was developing. The largest commercial landing of striped bass occurred in the 1940s with a total of 231,000 pounds landed in the 1945. During more recent times most of the commercial catch of striped bass occurred incidentally in gillnet fisheries for American shad. Restrictions on the legal size and breaking strength of gill nets in the American shad fishery after 1973 were designed to “minimize” the incidental catch of striped bass. Further action by the 1975 Oregon legislature prohibited any commercial landing of stripers.
Striped bass have added substantially to the diversity of recreational angling opportunities in the Coos Bay area. These are available at the times of year when salmonid species are not available and in areas of the bay, such as Isthmus and Catching sloughs, where no other fisheries exist. The recreational fishery for striped bass has fluctuated over the years with fluctuations in population level. The very successful spawn of stripers in 1940 produced an abundance of adults throughout the 1940s. A joint Fish Commission-Game Commission report recorded a recreational catch of 7,168 striped bass weighing 60,928 pounds during July and August 1949. A recreational catch of about 5,000 stripers was estimated for the 1959 season in Coos Bay. Those two estimates are the only estimates available for the recreational catch of striped bass in the Coos River system. Morgan and B\Gerlach (1950) described the striped bass fishery as a “combination of boat and bank fishing.” The report described the boast fishery as limited because of the “scarcity of skiffs.” “Seven boat liveries on the bay…could supply a total of 38 skiffs, two inboards, and four launches.” (Note – In Coos Bay-North Bend five to seven sporting good stories operated.) A fishing lodge named Bass Harbor Lodge was located on Isthmus Slough because of the bass fishery, and bass tournaments were periodically held in Isthmus slough. Currently, in conjunction with the loss of the striped bass fishery, boats cannot be rented any where in the upper Coos River system.
Specific angling closures were adopted to protect an important wintering area for striped bass in Catching Slough and to protect spawning fish in South fork of the Coos and Millicoma rivers. The 1986 changes were made to protect the relatively small number of adults that remain in the bays, and further changes were made in 1989 for the same reason.
Recreational fishing regulation for striped bass in Coos Bay, 1914-90
Year Bag Limit Length Limit
1914-1946 No BAG No Length
1946-1949 15/day No Length
1950-1960 5/day No Length
1961-1977 5/day 16” Min.
1978-1988 3/day 16” Min.
1989-present 2/day 30” Min.
Abundance of striped bass in the Coos River system has experienced wide fluctuations because of infrequent “dominant” year classes. No dominant year class has occurred in the Coos River since 1958, and a general downward trend in the population has continued since the early 1960s. Estimated population seize has ranged from 69,000 adult bass in 1945 to the current level, which may be only a few thousand fish (Bill Mullarkey, ODFW, unpublished data) Estimates of adult striped bass, aged 3 and older, in the Coos River system based on catch per unit effort (CPUE) and 1950 population estimate.
Year Estimated Population
1945 69,028
1950 17,382
1960 25,409
1962 31,251
1963 43,048
1964 24,852
1973 7,813
Although striped bass are anadromous, little ocean movement of Oregon stipers is apparent. Tagging studies in the Coos and Umpqua rivers have shown almost no exchange of fish between the two systems. Although the populations in the Coos and Umpqua river systems have common origins, they now appear to be distinct. Striped bass are pelagic spawners that spawn in tidal portions of the Coos, South Fork of the Coos, and Millicoma rivers in May and June. Spawning usually occurs at night. Most Spawning occurs when water temperature is between 58 degrees and 70 degrees F. A high percentage of the population usually spawns over a period of a few days when desirable water temperature occurs. Egg incubation, hatching, and yolk absorption occur over 6 to 8 day period. The alevins are 5 mm long when they hatch and are free-swimming after the yolk is absorbed. Fry begin feeding on plankton at that time. (Note –These eggs, alevin, and fry can be feed for hungry migrating juvenile salmonids heading to the ocean). The critical period of development for striped bass is the first 30 to 60 days after spawning. Studies in Coos Bay and other areas of the United States have shown that the number of 2 to 3-inch juvenile striped bass recruited to the population each year directly determines the size of the adult population 3 to 10 years later. ODFW studies have shown very low recruitment of juvenile striped bass since 1979.
(Note-On the Coquille River this summer, Shannon Osbon our STEP biologist, with the help of STEP volunteers have been seining the lower river. So far no juvenile striped bass, indicating no recruitment through spawning in the Coquille River.)
A substantial percentage of the striped bass in the Coos River population contain both male and female gonads, and the percentage appears to be increasing in the 80s. Hermaphrodism are rare in the Umpqua population and occur in very small numbers in other populations of striped bass that have been studied in the United States. The higher degree of hermaphrodism in the Coos River population may be the result of inbreeding since the entire population probably started with a very small number of individuals. Next month – what does striped bass feed on?
Striped Bass and Salmonid Management Issues in
Coos Bay, Oregon 1986
By Ray Temple and Al Mirati ODFW
Paraphrased by Steve Pennington
Striped bass are not native to the West Coast, but appeared in Coos Bay in 1914, about 45 years after their introduction in California. Subsequently Coos Bay became one of the two major commercial and sport fishing area for striped bass north of San Fransicso Bay.
Striped bass eat a wide variety of fishes and invertebrates, including salmonids. The controversy mainly concerns effects of predatory striped bass on increased production of wild and hatchery salmonids in the Coos River system and Bay. This report is intended to present an objective review of available information regarding striped bass and salmonid interactions.
- Salmon and Steelhead Population Trends
When counts ( peak number of coho per mile) for all 11 streams are averaged for each year to obtain a fish per mile index for the system, a decline is apparent. (Later after this report was published it was discovered that the method of determining coho population had serious errors in the development by ODFW, poor ocean survival conditions, plus over fishing for coho in the ocean. Steve)
Coho Chinook Steelhead
Period Peak Count Period Peak Count Period Estimated Catches
1950’s 50.4 50-54 No data 60-64 1410
1960’s 36.3 55-59 No data 65-69 1207
60-64 2.8
65-69 4.6
1970’s 25.7 70-74 28.2 70-74 1963
75-79 44.8 75-79 2134
80-84 23.5 80-84 24.6 80-84 1147
Splash dams constructed to store water to flush logs downstream virtually eliminated chinook spawning in the South Coos River from 1941 to at least 1957 when they were removed. The three dams blocked fish runs and caused severe scouring of the streambed when the dams were breached and the logs “splashed” downstream to the estuary and saw mills. Fall chinook abundance declined to near zero in the 1950’s, but have made a strong recovery since that time. The decline was coincident with loss of spawning habitat and the recovery coincident with improving habitat. Loss and improvement of spawning habitat are believed to be primary causes of long-term trends in abundance of wild fall chinook.
The rearing potential of Coos Bay has been estimated at about 13,000,000 fall chinook fingerlings. (Nicholas) Available spawning habitat cannot produce the level of smolts, but the estuary might be fully seeded by releases of juveniles.
- Striped Bass
Most adult striped bass pass the winter in Catching and Isthmus sloughs and in the Coos River. These sloughs appear to provide the primary wintering habitat. Some adult striped bass are present in the upper riverine habitat in mid-winter/early spring. By March, rising water temperatures and increasing day length stimulate movement from wintering grounds toward spawning habitat in upper Coos River and the lower reaches of the Millicoma and South Coos rivers. Adult abundance is the slough declines in March and April, with the females appearing last on the spawning waters. Spawning occurs in mid-May through mid –June, with timing and intensity strongly influenced by weather and water conditions. Female bass tend to leave the spawning area for residence in the upper bay almost immediately after spawning. Male bass tend to remain in the upper area until spawnable females are depleted. In general, older fish (10lb or more) tolerate the lower temperatures and higher salinities of the lower bay.
Juvenile fish are much more constrained by temperature and salinity than are adults. During the first growing season and winter, juveniles tend to stay in the South Coos, Millicoma, and Coos Rivers. Wintering fish may distribute downstream as high waters force the salinity wedge downstream. Striped bass populations have dominant year classes. The strong year-classes occurred in the Coos only in 1940 and 1958: in the Umpqua in 1966 and perhaps 1940 and the mid-1950’s. Low annual juvenile recruitment levels for striped bass since 1978 appear to have been caused by high mortality from egg to fingerling stage. (Note from Steve. These very small striped bass and shad will be pray for wild and hatchery salmon smolt migrating from the upper river to the ocean during June, July, and Aug. Predation from salmon smolt may control bass population when bass have a good spawn, rather than older bass controlling salmon through predation of smolt. ODFW and Coquille River STEP has not found juvenile striped bass in their seining on the Coquille River for the last three years, indication no spawning striped bass on the Coquille.)
- Description of Stomach Sample Data
Striped bass stomachs have been sampled intermittently since at least 1930. Most of the stomachs originated in the commercial fishery, with substantial sampling from other sources only in 1949,1960, and 1977-85. Striped bass are very mobile, active predators which feed on a diverse array of organisms, with adults feeding primarily on fishes.
Example; Diet of Striped Bass for 1962 and 1963.
Stomachs April May June
1962 1963 1962 1963 1962
Number examined 726 440 307 290 211
Food items
Salmonids 54.8% 3.7% 13.2% 11.6% 1.6%
Perch 10.2% 23% 21.7% 20.8% 33.3%
Sculpins 17.2% 14.7% 2.5% 5% 6.2%
Flatfishes 5.6% 14.7% 2.5% 5% 0%
Smelt .3% 8.4% 6.0% 18.7% 22.5%
Shrimp 4.5% 28.9% 29.2% 3.1% 31%
Miscellaneous 1.4% 11.6% 10.4% 35.4% 10%
Unidentified fishes 5.9% 6.1% 13.9% 4.3% 4.7%
Empty stomach 64.6% 67% 73.9% 68.3% 88.2%
Hatchery release 1962 1963
Includes releases from
Millicoma Pond 451,192 393,677
Most of the samples of bass stomachs were collected from the commercial fishery in tidewater portions of the Coos and Millicoma rivers. The fishery occurred in April through June, overlapping the time of emigration of coho smolts. Most bass predation on smolts appears to have occurred in this area in spring. Area 2, the sloughs are limited but show an incidence of only .01 salmonid per bass.
A time association between striped bass abundance and reduced coho abundance can be seen on graphs of Larson Creek returns, and statistical analysis of average counts for Morgan and Marlow creeks show a similar time association for those streams. Many sources of mortality other than striped bass predation also acted on coho. A comparison of Coos system and Coquille system spawning ground trends for coho salmon show a similar reduction to the coastwide average in the 1961-1971 period. Striped bass abundance was greater in the Coquille in the mid-1950 and this was the historical peak on the Coquille based on catches per license permit. (48 pounds per license) The average in the 60’s was 37 pound average landing per licenses for striped bass. Given the forgoing, it can be included that striped bass did not cause the reduction in abundance in Coquille river, coho in the 1960’s. By inference can also be included similar patterns in coho abundance in the Coos system cannot clearly be attributed to striped bass.
4. Summary
No direct means of measuring the impact of striped bass predation on salmonids is available. Ideally, one would be able to correlate predator population size directly to changes in prey species abundance. Our measure of adult salmon escapement is not sensitive enough for comparisons of year-to-year variation of run size, nor do we have précis estimates of striped bass abundance. Comparisons among groups of years (1950’s vs 1970’s) do not provide unequivocal findings. In addition, predation by striped bass is far from the only source of salmon mortality. Damage to spawning and rearing habitat; predation from many other fishes, birds, and mammals; unfavorable ocean conditions; and sport and commercial fishing all take a toll. Definitively separating the effects of striped bass predation from other sources of salmon mortality on the basis of salmon escapement(spawning counts) values is not realistic.
Coquille River
Background
The striped bass is a potentially important game fish in the Coquille River. Although they are considered anadromous they apparently live in the Coquille River estuary throughout the year (McGie and Mullen 1979). Striped bass were introduced into the west coast waters in 1879 by planting juveniles in San Francisco Bay. They have worked their way northward to the point where occasional striped bass are taken in the state of Washington.
The current population level of adult striped bass in the Coquille River system is difficult to ascertain because there is no longer a commercial fishery (Table 29 lists the commercial catch from 1924 through 1975), no tagging requirement for sport-caught striped bass, and no method of counting spawners short of a statistical population estimate. The population of striped bass in the Coquille River basin has deteriorated from levels in the past. Al though no statistical creel surveys have been made for stirped bass in the Coquille River estuary, it is apparent from random spot checks that the sport fishery has declined dramatically in the last 15 years. There may have been subtle changes in the estuarine habitat of Coquille River estuary, but these changes have not been documented. The habitat for fingerling, sub-adult and adult striped bass appears to be underutilized by this species at this time.
Some possible explanations for the low rate of spawning success include: 1) Channel deepening projects in Coquille River estuary may have changed the salinity regime to one that is unfavorable for survival of larval striped bass; 2) Extensive log storage and handling in the spawning area has changed the riverine environment during the spawning period; 3) inbreeding may have reduced the reproductive potential of the Coquille River estuary population of striped bass; and 4) Natural environmental conditions have changed (ODFW 1992).
Table 29. Coquille River commercial striped bass landings in pounds from1940 through 1975.
Year Pounds Year Pounds
1940 91 1958 3,795
1941 2,629 1959 793
1942 1,895 1960 859
1943 1,282 1961 529
1944 1,043 1962 2,012
1945 763 1963 1,399
1946 850 1964 485
1947 1,512 1965 190
1948 14,306 1966 630
1949 269 1967 1,093
1950 172 1968 498
1951 123 1969 756
1952 207 1970 395
1953 3,795 1971 537
1954 1472 1972 —
1955 2287 1973 445
1956 490 1974 —
1957 389 1975 397
What Effects does striped bass have on Salmon and Steelhead?
In the last 50 year I have head a lot of talk about striped bass and what effect they have on juvenile salmon and steelhead. So in the next couple of months I hope to give out some historical and personal experience with striped bass. This article will be about the history of Stripers on the Coos.
Steve Pennington