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


Sebastian, D.C.  1988.  Steelhead production characteristics of the 
Babine River and tributaries, 1987.  Prov. B.C. Proj. Rep. No. 

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 

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. 

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. 

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.