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 g/L Chl a) than in nearby control lakes (0.5-2.0 g/L Chl a).  Average 
(May-August) chlorophyll a concentrations in 1988 (8.0 g/L) were similar to the past 
two fertilization years (ll.9 g/L, 1987; 6.9 g/L, 1986; 3.6 g/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 kgha-1yr-1 in East Twin Lake (z = 2.9 m) and 2.9 kgha-1yr-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.