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 - FAIU Sebastian, D.C. 1988. Steelhead production characteristics of the Babine River and tributaries, 1987. Prov. B.C. Proj. Rep. No. FAIU-09:74p. A juvenile steelhead stock assessment and habitat inventory of the Babine River System at August, 1987, base flows was used to assess the vulnerability of the stock to proposed industrial development and potential over harvest. Wide ranges in fish densities and potential smolt production were attributed to differences in temperature, water quality and usable habitat. Steelhead fry densities in "useable" habitat were 10 to 30 times greater in non-glacial than glacial streams. The mainstem Babine River supported approximately 67% of the fry population and 80% of total smolt yield. Nichyeskwa and Boucher creeks were identified as the most important tributaries for steelhead production. At carrying capacity, 1,488,000 fry should translate to approximately 111,000 smolts and 13,400 adults before harvest for the system. Optimal escapement was estimated at 4,200 adults, including a 50% safety margin. On a provincial scale, Babine River is a moderately productive system. It appears the stock can withstand an average exploitation rate of up to 2:1 with no major impacts on full seeding requirements. Recommendations were made for habitat protection and further assessment. Tredger, C.D. 1988. Okanagan Lake tributary assessment. Progress in 1987. Prov. B.C. Fish. Proj. Rep. No. FAIU-10:31p. A three year program to assess fisheries enhancement opportunities in Okanagan Lake tributary streams was initiated in 1986 by the Fisheries Assessment and Improvement Unit. Initial investigations were undertaken on Mission, Powers and Peachland creeks. In 1987, the study included Mission, Powers, Peachland, Lambly, Shorts and Trepanier creeks. Objectives of the program were to assess current habitat conditions and stream fish production capacity relative to existing fish populations, and to identify factors limiting fish production, including streamflow. The methodology centred on a modified IFIM approach, in which weighted usable area at stream transects was calculated. Transect data was collected at each stream at flow stages encountered during the surveys, with the exception of Mission Creek, where hydraulic modelling information was available. Results are presented detailing stream width and weighted usable area at transects in each stream. Data is extrapolated to estimate total and usable stream area, and estimated capacity for kokanee spawning and juvenile trout rearing at the flow stages encountered. Recommendations for work to be conducted in 1988 are included. Ptolemy, R.A. 1988. Low angler catch of steelhead from Vancouver Island's largest river. The Nimpkish - an analysis of a paradox in smolt production. Prov. B.C. Fish. Proj. Rep. No. FAIU-11:76p. Steelhead smolt production at present and full seeding levels is estimated from preliminary data on survival rates and space requirements of juvenile trout (pre-smolts) summarized from the literature and B.C. data files. Average maximum production of smolts for the Nimpkish River on Northern Vancouver Island was approximated as 0.5 to 0.6 smolts 100 m-2 total wetted area (late summer) for 3.5 year old fish. Poor smolt yield is related to cold stream temperature (older smolts), highly dilute water chemistry (T. ALK. = 10 mg/L, TDS = 13 mg/L) at baseflows, and limited suitable habitat for both fry and parr stages. The recognized coast-wide average is 2.0 smolts 100-2. The reported mean fecundity was unusually high at 5,800 eggs per female from a limited sample size (13) of large adults. The minimum egg deposition and adult run size recommended for naturally sustained, maximum production of smolts are 6.6 million eggs and 2,271 adults. Since the total stream area used by steelhead juveniles is near 632 ha by stream order analysis, the minimum required egg deposition is 104 eggs 100 m-2 which includes an addition of 50% due to environmental/measurement uncertainty. The required escapement to produce this deposition may be larger if the true eff-to-fry survival is less than 15% and/or the average fecundity more closely resembles the Vancouver Island average of 4,000 eggs per female. A worst case scenario would have the maximum ratio of catch (harvest):escapement as 0.4:1.0 for a population sustained by pristine habitat; the Nimpkish watershed has been extensively logged and has sustained the recreational activities of three large logging camps. The potential carrying capacity was roughly estimated at 0.66 million fry and 0.21 million parr. Based on low and highly variable habitat saturation measures, the contemporary run size is roughly 1,400 adults. The minimum run size is expected to be closer to 3,600 adults at stream capacity. A pilot fry stocking project is detailed and habitat enhancement measures are discussed. A need to verify estimates of maximum juvenile abundance in ideal habitat can be satisfied by the control of recruitment in selected reaches. A further need to better quantify true fecundity is identified, which may result from future brood- stock collection. Tredger, C.D. 1989. Fish production capacity in Mission Creek at 4 modelled discharge levels. Prov. B.C. Fish. Proj. Rep. No. FAIU-12:64p. Weighted usable area and stream capacity for kokanee spawning and juvenile rainbow trout rearing was estimated at 4 discharge levels of fish production relative to current populations, and options for enhancement. Hydraulic conditions were simulated using the HEC-2 model at discharges covering a geometric series from 6 to 44% mean annual discharge (MAD). Results indicate the maximum capacity for kokanee spawning occurred at 1.42 m^3/s (22% MAD), and was approximately 330,000 fish. Current kokanee escapements were below carrying capacity at all flows simulated. Maximum capacity for juvenile trout was expressed at 0.42 m^3/s (6% MAD) for fry and 1.42 m^3/s (22% MAD) for parr. Application of theoretical survival biostandards to capacity estimates implied that potential trout migrant production to Okanagan Lake was limited by the amount and quality of parr habitat. Recommendations include a target summer/fall minimum flow of 1.42 m^3/s, spawning gravel improvements to Reach 1, and cover (boulder) installation to high gradient channelized reaches. Sebastian, D.C. 1989. An analysis of rainbow trout (Oncorhynchus mykiss production in the Kettle River in south central B.C. Prov.B.C. Fish. Proj. Rep. No. FAIU-13:51p. A fisheries investigation was conducted on the Kettle River upstream of Midway to assess habitat capability and the stock status of resident rainbow trout. Juvenile and adult populations were assessed using a combination of electrofishing and snorkelling during late summer of 1987 and 1988. The abundance of fry was extremely low in the mainstem (0-7 fish/100 m2), while parr abundance appeared to be reasonable at sites with adequate cover (5-14 fish/100 m2). Densities of catchable size fish were consistently low during both years, except for in the West Kettle River during 1987. The absence of older age classes indicates a problem with over harvesting. Below average summer flows during both study years reduced the proportion of suitable habitat for catchable size fish. The HQI method (Binns, 1982) suggested optimum densities of 6 kg/ha for the lower Kettle River, 12 kg/ha for the mid Kettle River and 21 kg/ha for the West Kettle River. Differences in habitat capability between stream reaches were related primarily to stream size and cover. HQI estimates suggest populations of 32,000 fish for the Kettle River and 14,000 for the West Kettle river, given an average catchable size of 150 grams (24 cm). The model indicated populations were at 20% or less of capacity in the main Kettle River. Fish sampling was inadequate to assess stock status in the West Kettle River. Pilot stockings of non- migratory interior stream stocks (i.e., Blackwater and Upper Dean) into the Kettle have been proposed to rehabilitate the fishery. A combination of stocking and more restrictive regulations are required to restore the trout fishery in the Kettle River. It is recommended that full scale stocking strategies be developed following results of the pilot stocking program. Ptolemy, R.A. 1989. Effects of highway construction and mitigation on summer steelhead in the Coquihalla River, British Columbia. Prov. B.C. Fish. Proj. Rep. No. FAIU-14:210p. The efficacy of habitat improvement techniques on a large, high gradient, and volatile coastal river was examined during the summers of 1985 to 1987. Juvenile and adult summer steelhead trout (Oncorhynchus mykiss) abundance was estimated before and after construction of a 110 km/hr four-lane highway. The impacts of three major diversions and numerous highway encroachments on fish habitat were evaluated. Habitat mitigation employed over-sized (>1 m dia.) keyed-in rip-rap in channelized reaches forming revetments, purs (deflectors) and boulder groupings in a variety of configurations. Detailed habitat measurements, direct snorkel surveys, juvenile electrofishing and mathematical modelling of habitat (PHABSIM), calibrated with juvenile steelhead abundance densities, demonstrated that mitigation structures sustained higher densities of fish than untreated areas. However, mass bed load movement of sand (<6.3 mm dia.) from construction appeared to severely reduce fish abundance (65%) and growth by sedimentation and embedding of boulder habitat. A large net decrease in bed material size (d90) was measured in reaches affected by channelization resulting in a reduction in parr habitat. None of the mitigation treatments employed were successful in re-creating high quality parr habitat. Negative long-term effects of construction in altered actions of stream increase with degree of habitat alteration through channelization and encroachments. Widespread impacts of sedimentation from road construction resulted in a severe reduction of habitat and stream carrying capacity from 1985 to 1987, reducing six year classes of steelhead production. Post study period monitoring suggests a slow recovery from sedimentation with improved fish abundance. Tredger, C.D. 1989. Okanagan Lake tributary assessment. Prov. B.C. Fish. Proj. Rep. No. FAIU-15:23p. Stream habitat quality and potential fish production was identified over a range of flow conditions in Lambly, Shorts and Trepanier creeks by estimating weighted usable width at established stream transects. Available habitat and capacity is reported relative to discharge levels. Limited kokanee spawning habitat was available in Lambly and Trepanier creeks at all flows sampled due to large substrate size. Significant potential exists for kokanee spawning in Shorts Creek. Rainbow trout production to Okanagan Lake appears limited by the amount of parr habitat in all streams studied. Potential production increased with flow over the range sampled. Sebastian, D.C. 1990. Juvenile rainbow trout production in the Horsefly River, the largest tributary to Quesnel Lake, B.C. Prov. B.C. Fish. Proj. Rep. No. FAIU-16:62p. Juvenile rainbow stock assessment was conducted on the Horsefly River system to determine current abundance and to estimate potential juvenile migrant production to Quesnel Lake using a habitat capability model for steelhead. The study involved a stock and habitat assessment during late summer of 1987, followed by juvenile stock monitoring at index stations during 1988 and 1989. Assuming identical habitat requirements by rainbow trout and steelhead, approximately 237,000 fry and 54,000 yearling migrants potentially could be produced annually. Current fry abundance in the mainstem Horsefly ranged from near 50% during 1987 and 1988 to approximately 85% of habitat capacity during 1989. Application of provincial biostandards indicates adult production of 1,600 to 4,000 fish and estimates a minimum required escapement of 550 fish. Opportunities for enhancement and recommendations for further juvenile assessment are discussed. Tredger, C.D. 1990. Small lakes index management: Analysis of 1989 results. Prov. B.C. Fish. Proj. Rep. No. FAIU-17:45p. Summer angling effort was established on approximately 400 lakes in south central British Columbia in 1989 using aerial boat counts. Estimates are presented in graphical and tabular form in relation to lake size, potential fish production and stocking rates. These analyses are intended to provide a diagnostic tool for the management and evaluation of small lake fisheries.