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 PROJECT REPORTS - RESEARCH Ward, B.R. 1989. Trends and forecasts of winter-run steelhead at the Keogh River: Results from 1988. Prov. B.C. Fish. Proj. Rep. No. RD-18:6p. Monitoring of the wild steelhead smolts and adults at the Keogh River continued in 1988. Smolt yield was low (3,324) from post-fertilization production. Size-at-age of smolts was similar to pre-fertilization years. The spawning population was large (1,800), and higher than expected based on the number and sizes of smolts that had left. The spawning population was comprised of a majority of fish hat had spent three years in the ocean (70% of the females and 55% of the males), with about 20% (twice the historical average) of the population comprised of repeat spawners. Very good conditions of survival in the ocean were indicated. Forecasted run sizes are for a continued abundance of spawners in 1989, but by 1990 the effects of relatively low smolt yield will likely result in below average returns of maiden fish. Adding to these runs will be repeat spawning fish and returns of about 1,000 and 600 adults in 1989 and 1990 respectively, from hatchery releases. Ashley, K.I., and N.T. Johnston. 1989. Habitat Conservation Fund, Technical Progress Report (1988-1989). Salsbury Lake Fertilization Project. Prov. B.C. Fish. Proj. Rep. No. RD-19:17p. Nutrient addition continued in the fourth year of a four-year pilot project, at a rate of 565 mg P/m2/5.4 mo and 2,039 mg N/m2/5.4 mo (8.5:1 N to P atomic weight ratio). Agricultural grade ammonium phosphate (11-55-0 and 12-51-0), technical grade mono- ammonium phosphate (12-61-0) and agricultural grade ammonium nitrate (34-0-0 and 34.5-0-0) were added weekly (April 26 to October 6, 1988) to a floating screen bottomed (153 um) box anchored in the deep end of Salsbury Lake. The nutrients were held in the epilimnion while dissolving, and sampling indicated they dispersed throughout the epilimnion. Summer phytoplankton densities were considerably higher in Salsbury Lake (2.1-15.5 µg/L Chl a) than in nearby control lakes (0.5-2.0 µg/L Chl a). Average (May-August) chlorophyll a concentrations in 1988 (8.0 µg/L) were similar to the past two fertilization years (ll.9 µg/L, 1987; 6.9 µg/L, 1986; 3.6 µg/L, 1985), suggesting the lake is reaching a new equilibrium level of production. Maximum zooplankton densities were much higher in Salsbury Lake (25,000/m3) as compared to the control lakes (1,550 to 5,300/m3). Mean size-at-age for wild and stocked kokanee has increased with duration of exposure to the fertilization treatment. Older age class (3+) rainbow trout are considerably larger in Salsbury Lake than in the two control lakes. Ashley, K.I. 1989. The use of chlorine as a possible fish toxicant. Prov. B.C. Fish. Proj. Rep. No. RD-20:14p. The use of chemical fish toxicants for coarse fish control is an accepted fisheries management practice in North America. In British Columbia the use of rotenone based fish toxicants is complicated by at least three factors: uncertainty of supply, cost escalations and increased concern about the effects and fate of chemicals used in lake rehabilitation programs. The need for chemical fish toxicants is valid in specific circumstances, and a literature review of approximately thirty chemicals used as fish toxicants suggests that chlorine may be useful as a limited purpose fish toxicant. Chlorine hydrolyzes to form hypochlorous acid (HOCl) when added to ammonia free water, which then dissociates and maintains an equilibrium with hypochlorite ion (OCl- 1). The relative concentration of each form is determined by the pH and temperature of the water. Chlorine combines with ammonia to form chloramines, and being a strong oxidizing agent chlorine will react with reducing compounds present in lentic environments (e.g., H2S). Laboratory bioassays indicate chlorine is quite toxic to fish with 96 hr LC50 values ranging from 0.172 mg/L for rainbow trout (Salmo gairdneri) to 1.41 mg/L for black bullhead (Ictalurus melas). The primary toxicological mechanism of chlorine is oxidation of reduced iron (Fe+2) in hemoglobin to methemoglobin (Fe+3), resulting in an inability of the blood to carry sufficient oxygen and subsequent death by anoxia. At least three field tests have been conducted with results ranging from partial to complete kills, depending on the chlorine demand and concentration of residual chlorine in the water column. Chlorine may be a usefully fish toxicant in limited situations where conventional fish toxicants should not be used (e.g., drinking water sources) and the water body is quite small. Tsumura, K., V.E. Blann, and C.A. Lamont. 1989. Progeny test of masculinized female rainbow trout having functional gonoducts. Prov. B.C. Fish. Proj. Rep. RD- 21:5p. Progeny tests conducted on masculinized female-only rainbow trout (XX males) having functional gonoducts indicate they produce monosex female sperm similar to other known XX male gonad forms. Occurrence of male and female offspring were compared in five XX male gonad groups separated according to shape, condition of the gonoducts and age of males. The shape of XX male testes ranged from abnormally globular and rounded to elongated. All XX male gonad groups had gonoducts that were occluded in three and functional in two of the groups. Progeny identifiable for sex in the gonad groups with occluded gonoducts consisted of 100% female fish. Progeny identifiable for sex in the two groups with testes form similar to those in untreated normal males consisted of 86% and 100% female fish. Percent of progeny in which sex could not be determined at time of examination ranged from 3% to 12% in the different gonad groups. Blann, V.E., and K. Tsumura. 1989. Rainbow trout broodstocks for coarse fish lakes. Habitat Conservation Fund Progress Report (1989-1990). Prov. B.C. Fish. Proj. Rep. No. RD-22:9p. In the second year of the coarse fish broodstock project, a comprehensive evaluation of Blackwater River rainbow trout stocks was initiated. Seven lakes containing coarse fish were stocked with Blackwater River and Pennask Lake (control) stocks in equal numbers in May, 1989. Growth, relative survival and maturity of these two stocks were compared at the end of one growing season. Blackwater River stock grew up to 6% larger (t-test, p<0.01) than the Pennask strain in 6 lakes, but relative survival ranged from 1.2:1 Pennask to Blackwater in Gladstone Lake, to 9.8:1 in Pear Lake, at age-1+. Age-2+ Blackwater stock from the 1988 stocking in Garcia and Mathew lakes were 2.7 times larger, by average weight, than the Pennask strain fish. Relative survival of the age-2+ fish, however, was 4:1 and 3.5:1 Pennask Lake to Blackwater River stock, in Mathew and Garcia lakes. Coarse fish were found in gut samples of 1% of the total age- 1+ Blackwater stocks, and 21% of age-2+ Blackwater fish. No fish were found in stomachs of Pennask Lake stock of either age class. Early sexual maturity appeared to be lake specific, not strain dependent, in this study. Brood fish were collected from Bootjack, Tzenzaicut, and Tsuniah lakes. Progeny from these broodfish and Blackwater River stock will be liberated as 1+ fish along with the Pennask stock, for further comparisons, in the spring of 1990. Parkinson, E.A. 1990. A framework for wild stock management of rainbow trout in small B.C. lakes. Prov. B.C. Fish. Proj. Rep. No. RD-23:10p. A working hypothesis suggests that wild rainbow stocks in monoculture and coarse fish lakes represent two fundamentally different management situations. Within these two categories the ratio of lake area to stream spawning and rearing area is the key driving variable. In comparison with monoculture lakes, coarse fish lakes are hypothesized to have lower stock productivity and an exacerbated effect of size on survival. As a result, rainbow stocks in coarse fish lakes are more prone to population collapse and more dependent on streams as rearing areas for juveniles. If true, this implies that avoiding population collapse and protection of stream rearing habitat are key management problems on coarse fish lakes. In contrast, excessive juvenile recruitment and an insensitivity to high rates of exploitation should be more characteristic of monoculture lakes. Blann, V.E., T.I. Godin, and K. Tsumura. 1990. Rainbow trout broodstocks for coarse fish lakes. Habitat Conservation Fund Progress Report (1990-91). Prov. B.C. Fish. Proj. Rep. No. RD-24:30p. Performance of wild rainbow trout (Oncorhynchus mykiss) from the Blackwater River and Tsuniah, Bootjack and Tzenzaibut lakes (coarse fish lake strains) was compared to the Pennask Lake strain (monoculture) in eight study lakes having minnow and/or sucker populations. Two coarse fish lake strains and a control (Pennask) strain were stocked as yearlings in each study lake between mid-May and early June. Growth and relative survival of the strains were compared after a five month growth period. Age 1+, Blackwater fish were significantly larger than Pennask fish in the four study lakes in which both were stocked. Tzenzaicut strain was significantly larger than Pennask in three of the five study lakes. Tsuniah Lake rainbow trout strain were significantly heavier, but not larger than Pennask strain fish in two of four lakes in which these strains were stocked. No significant size difference was found between Bootjack and Pennask fish in any of the four lakes in which both were stocked. Relative survival was significantly higher for rainbow trout strains originating from a coarse fish lake than Pennask strain in five lakes, but was similar in three lakes. Evidence of fish consumption was found at age 1+ in all rainbow trout strains originating from coarse fish lakes. Fish were not found in guts of Pennask trout until age 2+. Slaney, P.A., and T. Godin. 1989. Sumallo River stocking evaluation: progress 1989. Prov. B.C. Fish. Proj. Rep. No. RD-25:27p. The introduction of a resident strain of yearling rainbow trout into the Sumallo River was evaluated during summer to fall, 1989. A fence was operated to assess migration and fish were enumerated in the stream by use of underwater counts supplemented with electrofishing. A small proportion (9%) of the 7,000 fish that were stocked, migrated from the Sumallo into the Skagit River. Significant numbers of wild rainbow, comprised of mainly juveniles, also migrated suggesting that the Sumallo is providing recruitment to Ross Reservoir. Underwater census of hatchery and wild trout was not useful as a population enumeration technique because most fish moved deep into cover in association with the cool (10 C) summer temperature regime. Sampling of stocked rainbow trout in the fall indicated that growth was meagre. Further stocking should be deferred until the 1989 cohort, as well as returns from the 1988 stocking of Skagit migrant strain, are more intensely assessed in 1990. Rosenau, M.L., and P.A. Slaney. 1991. A population assessment and stocking evaluation of rainbow trout in the Sumallo River. Prov. B.C. Fish. Proj. Rep. No. 26:85p. An investigation of rainbow trout populations in the Sumallo River, a major upstream tributary of the Skagit River, British Columbia, was conducted to assess the survival, size and abundance of two hatchery strains of rainbow trout (Skagit and Blackwater, stocked in 1988 and 1989, respectively) and to examine life history patterns of wild rainbow trout (Oncorhynchus mykiss) and Dolly Varden char (Salvelinus malma). A fish enumeration fence was operated to monitor emigrants and immigrants, and a mark-recapture survey was conducted on a representative 3 km section. Fishable sections were intensely angled and minnow-trapped, and growth patterns were analyzed from samples of fish scales. Few hatchery fish of either strain were captured in the Sumallo and Skagit Rivers; all were captured by angling and electroshocking and none by trapping. Both strains were stocked at a mean length of 134 mm, while average lengths at recapture were 315 (Skagit) and 194 mm (Blackwater); the larger increase of the Skagit strain probably resulting from accelerated growth in Ross Lake. Estimated numbers of Blackwater trout remaining in the Sumallo River during September, 1990 were very low (162 fish; 0.3% of all rainbow trout or 2.3% of those stocked). The downstream migration of wild rainbow trout was comprised of four age classes including 1+ (mean length, 97 mm), 2+ (126 mm), 3+ (149 mm) and 4+ (187 mm). Based on scale analysis, length-frequency distributions, and a comparison of age and growth with a nearby non-migratory fluvial population of rainbow trout (upper Skagit), most adult rainbow trout (>200 mm) in the Sumallo were migratory and had undergone a period of lake growth before returning to their natal stream to spawn or feed, or adfluvial-lacustrine. Back-calculations from scale samples indicated there was a strong positive relationship between size and survival, thereby the larger and older juveniles disproportionately contributing to the adult trout population. The density and biomass of juvenile rainbow trout and Dolly Varden charr during late September were 0.032 fish/m2 and 0.53 g/m2, and 0.040 fish/m2 and 0.62 g/m2, respectively, which are low compared to most trout streams. Extreme phosphorus deficiency (<1-2 ppb concentration in summer) and, secondarily, a relatively low summer temperature regime (ca. 10 C) are the main limitations to production of trout and charr of the Sumallo River. Management implications and options are summarized. Tsumura, K., and T.I. Godin. 1991. Evaluation of rainbow trout strains in small coarse fish lakes. Three year summary: 1988 to 1990. Prov. B.C. Fish. Proj. Rep. No. 28:40p. Growth and relative survival of progeny from wild rainbow trout (Oncorhynchus mykiss) strains originating from coarse fish environments have been compared to the standard Pennask trout strain (wild, monoculture) for three years. Mean size of "coarse fish" rainbow trout strains indicate faster growth in length and weight than Pennask trout during the first and second year after release into a lake, in most cases. However, recoveries of the "coarse fish" trout strains relative to the Pennask strain has been variable to date. This comparison may be confounded by differences in mean size at release, differences in stocking density between years, behavioural differences that affect catchability and other unknown factors. Early male maturation does not appear to be a problem for strains compared over three years. The Blackwater trout strain matures extensively at age 3 and all have matured by age 4. About 50% of the Pennask trout also mature at age 3 but the remainder mature at age 4 or older. Proportion of rainbow trout with fish in the gut recovered at age 1+ ranged from <1 to 10% for the "coarse fish" trout strains. Coarse fish were not found in the gut of Pennask trout until age 2+. Johnston, N.T., K.I. Ashley, and K. Tsumura. 1991. Survival, growth and yield of rainbow trout (Oncorhynchus mykiss) in the Twin Lakes, southwestern British Columbia, prior to lake fertilization. Prov. B.C. Fish. Proj. Rep. No. RD-29:31p. Known numbers of marked, F1 progeny of wild-stock rainbow trout were introduced as fall fry (1982-83) or yearlings (1984-89) into two adjacent, small, oligotrophic, coastal montane lakes with similar low concentrations of inorganic nutrients but different morphometries (z = 2.9 and 12.5 m). Survival, growth and yield were monitored by total removal and restocking. Minimum survival to age 2 was independent of size-at- stocking between 2 and 38 g, and did not vary between the two lakes. The average survival to age 2 was 42%. Instantaneous growth rates varied inversely with initial mean sizes and with initial standing crops, and were significantly lower in the deeper lake. Yield average 6.9 kgáha-1áyr-1 in East Twin Lake (z = 2.9 m) and 2.9 kgáha-1áyr-1 in West Twin Lake (z = 12.5 m). Power analysis of a proposed fertilization experiment indicated that four years of sampling would permit the detection of two-fold or greater yield with 95% power.