Abstracts of Fisheries Management Reports, Technical Circulars and Project Reports of the Fisheries Branch Daiva O. Zaldokas & Debra L. Aird B.C. Fisheries Branch, 2204 Main Mall, U.B.C., Vancouver, B.C. V6T 1Z4 Fisheries Technical Circular No. 91 1992 FISHERIES TECHNICAL CIRCULARS Tredger, C.D., R.P. Griffith, and J.C. Wightman. 1989. Detoxification and decontamination of waters following chemical rehabilitation with Noxfish. Prov. B.C. Fish. Tech. Circ. No. 84:8p. Water samples were collected from three lakes which were chemically rehabilitated in 1986 by the Province of British Columbia, Ministry of Environment, Recreational Fisheries Branch. Samples were analyzed for rotenone and the Noxfish diluent, to determine both persistence and rate of detoxification. Results indicated that both rotenone and the Noxfish diluent were essentially non detectable in water samples taken 7 months after fall treatments. The rates at which rotenone became non detectable ranged from 17 to at least 77 days. The Noxfish diluent reappeared after some period of absence in 2 lakes, including detection the following spring. It was recommended that routine water sampling occur where waters are used for domestic purposes, and that monitoring programs similar to this be continued and expanded to cover other piscicide formulations as used. Further programs to determine inert ingredient dissipation rates, pathways within lake systems for uptake and release of inert ingredients, and toxicity of inert ingredients to non target organisms are also required. Billings, S.J. 1989. Steelhead harvest analysis, 1987-88. Prov. B.C. Fish. Tech. Circ. No. 85:45p. Since 1966-67, at the end of the angling licence year, a questionnaire has been sent to a sample of anglers who fished for steelhead in British Columbia. Information was requested on their fishing activity and catch success and incorporated into an annual summary of steelhead sport catch. Over this time there have been considerable changes in licence sales, the number of days spent fishing, catch and release of steelhead, and freshwater angling regulations in B.C. In the 1987-88 season, 31,263 steelhead angling licences were sold, 11% of which were to nonresidents of B.C. Questionnaires were sent to 56% of licensees and a response was received from 55% of those contacted. Of the respondents, 74% reported going steelhead fishing and 60% of these `active' anglers successfully landed a fish. The provincial steelhead catch has increased significantly since 1982. In the 1987-88 season, steelhead anglers fished for 258,101 days in the province catching 153,489 fish. Wild steelhead made up the largest component of the catch at 124,348 fish; hatchery catch numbered 29,141 fish. Catch per angler day was 0.62. Provincial catch and effort were down from previous year's (1986-87) record highs of 188,417 fish and 279,505 days. The increasing trend in steelhead catch in recent years is a combined result of increased stock abundance, sizeable returns of hatchery fish to some rivers, and repeated captures of released fish. The Chilliwack/Vedder River was, once again, the most heavily fished stream in the province with 54,171 angler days. This river supported more than half of all the steelhead fishing activity in the Lower Mainland. Reduced possession quotas as well as steelhead release regulations have resulted in a decreased proportion of the steelhead catch being kept. The ratio of fish kept has dropped from 63% in 1970-71 to under 13% in the last four years. Of the active anglers, 32% kept between one and five steelhead and only 2% kept more than five steelhead. The Chilliwack/Vedder River reported the most fish caught (23,795) followed by Stamp/Somass/Sproat (11,401), Dean (9,505), Cowichan (9,151), Bulkley (7,717), and Skeena (7,707) rivers. Overall, Vancouver Island reported the highest number of steelhead caught followed by the Skeena Mainland and Lower Mainland areas. Hatchery fish, in 1987-88, comprised 19% of the total provincial catch compared to 27% in the previous two years. The release ratio for hatchery fish averaged 70% compared to 94% for wild fish. Sawada, J.O., and B. Warner. 1989. Abstracts of fisheries management reports, technical circulars, and project reports of the Recreational Fisheries Branch, British Columbia Ministry of Environment 1985-88. Prov. B.C. Fish. Tech. Circ. No. 86:55p. This publication is a compilation of 9 Fisheries Management Reports, 18 Fisheries Technical Circulars and 96 Fisheries Project Reports of the Fisheries Branch of the British Columbia Ministry of Environment. Only reports dated 1985 through 1988 were included. Where abstracts were unavailable summaries, introductions or titles were used. The compilation was assembled from the files of the Research and Development Section of the Fisheries Branch, and may be incomplete. To aid in future publications of this kind, please ensure that a standard abstract is included in all reports. Parkinson, E.A. 1989. Errors in ageing hatchery rainbow trout from small lakes in southern British Columbia. Prov. B.C. Fish. Tech. Circ. No. 87:7p. The ability of readers to correctly age rainbow trout was tested using scales from hatchery trout marked and released as spring yearlings. After an initial learning phase, accuracy averaged 78% (range 73-85%). Neither the differences in accuracy among readers nor a tendency to underage was significant. Readers tended to make the same errors on individual scales, but most errors could be detected by discrepancies among pairs of readers. Errors in ageing had little effect on estimates of age structure or length at age 2+ for this data set in which readers discussed the true age of each scale before proceeding to the next. Estimated age structure was 16% 1+, 57% 2+ and 27% 3+ and older, whereas the true age structure was 18% 1+, 50% 2+ and 32% 3+ and older. Estimated and true mean lengths at age 2+ were 304 and 301 mm, respectively. The small size of these discrepancies may be due to prior expectations and the continual feedback on true values for this data set. Slaney, P.A., B.R. Ward, and L. Berg. 1990. A preliminary assessment of the effect of external abrasion on the smolt-to-adult survival of net-pen cultured steelhead trout. Prov. B.C. Fish. Tech. Circ. No.88:11p. The effect of external abrasion of smolts on the return rate of maiden adult steelhead (Oncorhynchus mykiss) was assessed in a preliminary experiment at the Keogh River in south coastal British Columbia. Abrasion was defined by the incidence of scale loss, fin abrasion and opercular abrasion. Smolts with "low abrasion" (7,300) and "moderate abrasion" (10,300) were marked and released at similar sizes in the lower Keogh River during early May, 1984. Based on population estimates of returning adults in 1986 and 1987, the survivals of the low and moderate abrasion groups were not significantly different: 8.7% and 7.2%, respectively. Both groups returned at similar mean lengths after 2- and 3- ocean years. In addition, recoveries of adults as upstream migrants and downstream kelts combined were examined for differences between the two abrasion groups. Recovery rates from the low and moderate abrasion groups were similar: 4.0 and 4.3%, respectively. Corresponding recoveries of age 2-ocean steelhead were 2.1 and 2.3%, and for 3-ocean fish, 1.9 and 2.0%. The established level of disparity of smolt abrasion was apparently insufficient to cause differential returns of adult steelhead. Ward, B.R., J.A. Burrows, and D.L. Quamme. 1990. Adult steelhead population size and salmonid migrants of the Keogh River during the spring, 1990. Prov. B.C. Fish. Tech. Circ. No. 89:29p. Data obtained in 1990 from a fish counting fence installed on the Keogh River, a coastal stream located on northeastern Vancouver Island near Port Hardy, B.C., added to more than a decade of information collected on wild steelhead trout (Oncorhynchus mykiss). The total number of wild adults in 1990 was estimated to be 1,374; the sex ratio of which was 1:1.1, female to male. Mean lengths and weights were obtained for wild spawners (males 795.4 mm, 5.8 kg; females 764.9 mm, 4.9 kg), and mean lengths were obtained for wild kelts (males 764.1 mm, females 758.6 mm). Wild fish were estimated to comprise 72% and hatchery fish 28% of the total steelhead run on the Keogh River. The migration of wild adult steelhead was biased to the late-run component, which was relatively abundant, yet preliminary estimates of oceanic survival were low for smolts which contributed to these returns. Preliminary returns of pen-reared smolts released early in May 1988 were compared to returns of fish which were released at the peak of wild steelhead smolts. After two years at sea, the later release returned at a rate twice that of the early release. All smolts were captured. Total captures of wild fish were low compared to averages in past years: steelhead smolts, 3,133 fish (mean length 166 mm, mean weight 40.8 g); steelhead parr, 757 (103 mm, 11.6 g); coho smolts, 57238 (103 mm, 11.4 g); cutthroat trout, 205 (156 mm, 38.1 g); Dolly Varden adults, 721 (259 mm, 126.6 g); Dolly Varden smolts, 3,200 (145 mm, 29.7 g); Dolly Varden parr, 50 (110 mm, 11.1 g); and cottids, 1,388 (125 mm, 30.7 g). Peak migrations were May 7 (505 fish) and June 2 (362) for steelhead smolts; May 7 (76), May 8 (75) and June 12 (60) for steelhead parr; and May 7 (6,305) for coho smolts. From May 16 to June 13, a total of 1,423 steelhead smolts (45.4% of those captured) were manually tagged in the adipose fin with sequentially coded wire tags to examine the relationships of smolts' size, sex, migration time, and age and their subsequent survival and age-at-return. From May 1-31 a total of 22,715 coho smolts (39.7%) were coded-wire tagged, with tag numbers stratified into three time periods, as in 1988. Balkwill, J.A. 1991. Limnological and fisheries surveys of lakes and ponds in British Columbia 1915-1990. Prov. B.C. Fish. Tech. Circ. No. 90:157p. An index to the 2,905 lakes and ponds in British Columbia that have been surveyed by the Ministry of Environment, Inventory Section and other provincial and federal agencies. Surveys range from a partial to full reconnaissance level survey and some lakes may be surveyed several times. The surveyed lakes are listed alphabetically along with the type of information available on each lake. Lirette, M.G. 1991. Angler harvest of lake char, kokanee and rainbow trout from Bridge Lake, 1990. B.C. Ministry of Environment, Lands and Parks, Fish. Tech. Cir. No. 92:19p. Between May and September, 1990, the recreational sport fishery on Bridge Lake was surveyed. Aerial boat counts were used to estimate angler use at 10,133 angler days. Effort in the 1990 fishery increased 30% over previous years. A total of 699 anglers were interviewed throughout the summer at a fishing resort and a provincial campground adjacent to the lake. The average number of anglers per boat was 1.86 and the average angler hours per angler was 4.0. Anglers spent an estimated 40,533 hours fishing to catch 4,965 lake char (0.12/hour), 4,154 kokanee (0.1/hour) and 1,216 rainbow trout (0.03/hour). Ninety-six percent of the sport fish caught by anglers were killed. The estimated total harvest for lake char was 5,000 kg or 3.6 kg per hectare of lake surface area. This was three to six times higher than the theoretical sustainable harvest for this species. Lake char in the creel and on the spawning beds averaged 45.8 and 45.3 cm fork length, respectively. Spawning lake char first mature at 7 years of age. They averaged 14 years old based on otolith samples and 9 years old based on scale samples. Ages have yet to be verified. Total lake char yield indicates over exploitation while age and growth data suggests a slow growing stunted population of lake char which has not been heavily impacted. A reduction in the regulated daily catch is recommended to offset increasing angling pressure on Bridge Lake. A total of eleven different food items were identified in 36 stomach samples of char from Bridge Lake. Zooplankton, and aquatic insects each occurred in 60% of the fish while only 8% of the lake char had eaten fish. The catch of kokanee and rainbow trout represented 5.0 and 0.9% of the fish stocked, respectively, into Bridge Lake. Management recommendations are discussed. Abbott, J.C. 1991. Feeding, aggression and growth in juvenile steelhead trout (Salmo gairdneri). Prov. B.C. Fish. Tech. Circ. No. 93:110p. Juvenile steelhead trout (Salmo gairdneri) compete for access to space and food, and the distribution of these resources within a population affects the relative growth and survival of individuals. Aggression is a means of competing for these limited resources. This thesis examines the causes of aggression and growth depensation (size divergence) in juvenile steelhead. The sizes of socially isolated juveniles diverged less with time than those of groups of interacting steelhead, although average growth rates were equivalent, indicating that the presence of competitors affects relative growth. A behaviourial mechanism resulting in unequal food acquisition or growth efficiency is indicated, as rations were in excess of requirements. Size-matched pairs of steelhead established hierarchies in which dominants grew 12.3% faster than subordinates although rations were equal. Therefore factors other than access to food (possibly stress) play a role in growth depensation. Groups of steelhead grew faster when the inter-feeding interval was reduced, even though daily ration was constant. Size divergence over time was unaffected at intervals ranging from 0.5 to 24-h. Marked increases in aggression were consistently observed following feeding. The magnitude of post-feeding peaks was inversely correlated with inter-feeding interval. Total daily aggression and frequency of various behaviours were unchanged. Learning of feeding times and anticipatory aggression were demonstrated by recording behaviour on the fifth day of a feeding schedule and continuing to monitor behaviour for one day after feeding was discontinued. Alpha and beta hierarchy positions were stable over a one week period. Underwater observation of steelhead in hatchery production facilities confirmed the occurrence of aggression. Various feeding regimes were presented to groups of steelhead in these facilities. No differences in growth, size divergence or fin damage were detected at four regular feeding intervals. Randomly fed fish showed less size divergence than regularly fed fish but had equivalent growth rates. This reduced growth depensation could result in a 6% increase in smolt production. Trout fighting tactics varied depending on the response of the opponent. Analysis of aggressive attacks and patterns of fin damage indicate that agonistic behaviour is the major cause of fin damage observed in culture facilities.