摘要:

Cytochrome P4501A induction was used to evaluate exposure of fish to bleached kraft mill effluent in experimental stream channels. Immunodetectable P4501A and associated ethoxyresorufin-O-deethylase (EROD) activity were elevated in largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus) throughout 263 days of exposure to 8% and 4% effluent from a mill that used 70% chlorine dioxide substitution for chlorine in the pulp bleaching process. In largemouth bass, P4501A was elevated as high as 55-fold over control fish. Large temporal and species variations were observed in enzyme levels and activity. Levels of chlorinated organic compounds present in effluent also varied throughout exposures. However, there was no apparent relationship between P4501A and any of those compounds measured. P4501A and EROD in channel catfish declined to control levels within seven days after transfer of fish to clean water or after terminating introduction of effluent into the channels. In another exposure, induction was observed in largemouth bass at 4 and 12% effluent after the mill began using oxygen in the delignification process and 100% substitution of chlorine dioxide for chlorine.

ISSN:0706-652X    

DOI:10.1139/f95-045

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

In vertically integrated samples (from ≤ 75 m) taken around and over Western Bank in November and December 1991, and January 1992, densities of larval cod (Gadus morhua) correlated with those of copepods, notably with relative densities of copepodids plus adults of predominant prey,Pseudocalanusspp. andParacalanus parvus.Pseudocalanusshowed a large increase from time of cod spawning but was concentrated over the bank through gyral circulation rather than enhanced productivity. Numbers of both copepods in stomachs of larvae < 10 mm were significantly related to their field densities, when controlled for sample month, larva size, and time of day. Stomach fullness was related to sample month, time of day, size of larva, and density ofPseudocalanus, but notP.parvus. Smaller larvae from four depths at four stations over the bank in late 1992, ate mostly nauplii ofPseudocalanusandCentropages typicus. Numbers eaten were strongly related to their field densities, weakly to sample depth, and not to larva size. Stomach fullness was positively related only to densities ofPseudocalanusnauplii. Larvae > 5–6 mm switched to larger prey, mostlyPseudocalanuscopepodids. More research is needed on interactions between copepod behaviour and the physical mechanisms that concentrate or disperse them on offshore banks.

ISSN:0706-652X    

DOI:10.1139/f95-046a

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Laboratory-based bioassays were conducted to determine concentrations of sodium-sulfate type salinities that limit the hatching success of several fish species. Survival to hatching (SH) was significantly lower (P < 0.05) in sodium-sulfate type waters from Devils Lake, North Dakota, of ≥ 2400 mg/L total dissolved solids (TDS) than in fresh water of 200 mg/L. In waters of 200, 1150, 2400, 4250, and 6350 mg/L TDS, walleye (Stizostedion vitreum) SH was 41, 38, 7, 1, and 0%; northern pike (Esox lucius) SH was 92, 68, 33, 2, and 0%; yellow perch (Perca flavescens) SH was 88, 70, 73, 0, and 0%; white sucker (Catostomus commersoni) SH was 87, 95, 66, 0, and 0%; common carp (Cyprinus carpio) SH was 71, 69, 49, 63, and 25%.

ISSN:0706-652X    

DOI:10.1139/f95-047

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

We examined the effects of ambient temperature (10, 20, and 30 °C) and relative humidity (10, 50, and 95% RH) on the aerial exposure tolerance of adult zebra mussel (Dreissena polymorpha) and quagga mussel (D.bugensis) collected from the St. Lawrence River. Survivorship of mussels in air significantly increased with increasing RH, decreasing temperature, and increasing mussel size. At 20 °C and 50% RH (early temperate summer conditions), large (21–28 mm)D.polymorphasurvived more than 5 days exposure, whereas small (10–18 mm)D.polymorphasurvived 1–3 days. Seventy-three percent of largeD.polymorphaand 10% of smallD.polymorphasurvived 10 days exposure at conditions considered optimal for survivorship (10 °C and 95% RH). Survivorship ofD.bugensiswas tested at 20 °C and was 15–100% lower than that ofD.polymorphaat all RH levels combined with exposures less than 5 days.Dreissena bugensisalso suffered significantly higher percent weight losses because of desiccation thanD.polymorpha. The differences in the desiccation tolerance of zebra and quagga mussels reflect their relative depth distribution in lakes. Our results suggest that, given temperate summer conditions, adultDreissenamay survive overland transport (e.g., on small trailered boats) to any location within 3–5 days' drive of infested waterbodies.

ISSN:0706-652X    

DOI:10.1139/f95-048

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

We analysed the relationship of length to age in a sample of 204 harp seals collected in 1976–1979 and of 437 animals collected in 1988–1992, by fitting asymptotic growth curves. The only significant variations were in asymptotic length, which for 1988–1992 was significantly larger for males (170.4 cm) than for females (165.3 cm). This sexual dimorphism was not significant in 1976–1979, because the fitted asymptotic length of females varied greatly from year to year, being large in the 1976–1979 samples. An index of body condition (total weight/length2.6) and a volume index constructed by regressing body weight on length × axillary girth squared indicated that harp seals collected in 1988–1992 were in poorer condition than animals collected during 1976–1979. Although this suggests a decline in available resources, the possibility of differences arising from sampling bias cannot be excluded.

ISSN:0706-652X    

DOI:10.1139/f95-049

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Pacific salmon are normally thought to be distributed throughout the Subarctic Pacific, an area where they form the dominant fish fauna. We use a series of generalized additive models to show that salmon exhibit a sharp step-function response to temperature in the oceanic eastern north Pacific in spring. The critical temperature defining the southern boundary varied by species: 10.4 °C for pink and chum salmon, 9.4 °C for coho salmon, and 8.9 °C for sockeye salmon. These thermal limits occur well to the north of the southern boundary of the Transition Zone, at widely separated geographic positions within the Subarctic Domain, and at temperatures much lower than the lethal upper limit for each species. The sharp decline in abundance with temperature, and the remarkably low temperatures at which the response occurs, suggests that thermal barriers form an effective limit to the offshore distribution of salmon in spring, and can limit the distribution of Pacific salmon to a relatively small area of the Subarctic Pacific. The strength of this response is presumably the direct result of strong evolutionary selection. Future temperature changes in the North Pacific could therefore have a direct impact on the production dynamics of Pacific salmon.

ISSN:0706-652X    

DOI:10.1139/f95-050

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

We used hydroacoustics to examine diel changes in the vertical distributions of rainbow smelt,Osmerus mordax, in Lake Memphremagog, Quebec/Vermont. Our objective was to evaluate hypotheses linking diel vertical movements of fish with light levels. Smelt distributions were also monitored from June through October (1988 and 1990) to evaluate seasonal changes in their behavior. A strong relationship (r2 = 0.83) between ambient light intensities and the upper fish layer in the water column was observed. Fish depth was also related to the depth of the thermocline during the night and when surface water temperatures were > 18 °C. The most characteristic feature was the strong avoidance of light levels > 0.1 μW/cm2. However, we found considerable variation in lower light levels experienced by the whole fish population. The results suggest that existing models of anti-predation behavior relating light and fish depth are consistent, with some limitations, with patterns of diel vertical migration in rainbow smelt.

ISSN:0706-652X    

DOI:10.1139/f95-051

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A single i.p. injection of 5 μg 3,3′,4,4′-tetrachlorobiphenyl (TCBP)/g body mass in adult brook trout (Salvelinus fontinalis) resulted in decreased (p < 0.0001) growth rate despite pair feeding. Plasma retinol decreased (p < 0.0037). Intestinal retinyl palmitate (RP) and 3,4-dehydroretinyl palmitate (DRP) concentrations decreased in TCBP-injected males (RP,p < 0.0143; DRP,p < 0.0009), whereas retinoid levels did not decrease significantly in TCBP-injected females. The RP:DRP ratio in trout liver increased (p < 0.0001). These results suggested that DRP is more sensitive than RP to the effects of TCBP. No significant differences in ovarian retinoids occurred in post-spawning trout. Field validation of the effects on intestinal retinoids was conducted with lake sturgeon (Acipenser fulvescens) caught at a contaminated site on the Des Prairies River near Montréal (St. Lawrence River population) and reference sturgeon taken from a site near the origin of the Ottawa River in LaVerendrye Park. Intestinal retinoid concentrations were lower (RP,p < 0.0008; DRP,p < 0.0004) in the St. Lawrence River sturgeon. Our results demonstrate that a coplanar PCB is capable of altering vitamin A dynamics in several tissues and organs, and may cause a lowering of retinoids in the intestine.

ISSN:0706-652X    

DOI:10.1139/f95-052

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Modelling the uptake and detoxification kinetics of phycotoxins in marine filter-feeding bivalve molluscs is discussed and illustrated by a case study involving blue mussels (Mytilus edulis) in the lower St. Lawrence estuary in eastern Canada. A dynamic model was fit to empirical data acquired on differential responses of mussels transplanted from sites characterized by differing history of exposure to toxigenic blooms responsible for paralytic shellfish poisoning (PSP). Although it is difficult to collect sufficient data to calibrate complicated models, it appears that one- and two-compartment models are fully adequate for this type of modelling. Measuring phycotoxin levels in shellfish can be a useful and cost-effective adjunct to direct monitoring of phytoplankton toxicity in the water column, because ongoing filtration by shellfish provides an integrated estimate of the toxin to which they are exposed.

ISSN:0706-652X    

DOI:10.1139/f95-053

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Four sockeye salmon (Oncorhynchus nerka), two chum salmon (O.keta), three pink salmon (O.gorbuscha), and four Chinook salmon (O.tshawytscha) with depth-sensing ultrasonic transmitters were tracked in the central Bering Sea to examine migration in the open sea. Ground speeds of maturing sockeye, chum, and pink salmon were at 0.54–0.66 m/s (0.88–1.17 fork lengths/s). Chinook salmon, probably immature fish, moved more slowly (0.34 m/s). Maturing individuals moved in particular directions and maintained their ground speeds and directions during day and night. The results also suggested that salmon had a compass orientation ability functioning without celestial information. Sockeye, chum, and pink salmon showed strong surface preferences but chinook salmon swam deeper (30–35 m) than did the other species.

ISSN:0706-652X    

DOI:10.1139/f95-054

出版商:NRC Research Press    

年代:1995

数据来源: NRC