摘要:

The physiological basis for well-known correlations between summer air temperature indices and year-class strength in northern smallmouth bass (Micropterus dolomieui) populations was examined. Field and laboratory studies demonstrated the existence of two critical stages in early life when smallmouth bass are particularly vulnerable to features characteristic of many natural water temperature regimes. The first stage extends from fertilization until the young leave the nest; high mortality results from exposure to extreme temperatures. The second stage extends over the first winter, when the young subsist on accumulated energy reserves. Because the ratio of energy stored to basal metabolic rate increases with size, large fish can withstand winter starvation better than small fish. The results from these and other studies were incorporated into a deterministic model of the relations between temperature and first-year survival of small-mouth bass. Analysis of water temperature time series data from many locations led to the development and parameterization of a stochastic model capable of simulating variations in water temperature characteristic of the littoral zones of typical North American lakes. The stochastic physical and deterministic biological models were used together to assess the effects on first-year survival of changes in climate and of realistic changes in the magnitude and frequency of short-term temperature fluctuations. The model successfully predicted the observed northern limit of the species' range. It also generated approximate environmental criteria for judging when year-to-year variation in survival, over one or both of the critical life history stages identified, is likely to reach a level sufficiently great to determine the pattern of year-to-year variation in recruitment to the adult stock. The combined model was also used to assess the effects of thermal loading from a nuclear power plant on a particular population.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<1:SSOTEO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Indices of year-class strength, stock size, and surplus production of female Dover sole (Microstomus pacificus) and female English sole (Parophrys vetulus) were calculated by two methods: Catch per unit effort (CPUE) and cohort analysis. For each species we derived two CPUE indices and two cohort analysis indices based on different age-groups. For Dover sole, both CPUE indices show strong year classes in the early and mid-1940's, declining recruitment in the late 1940's and early 1950's and an increase in strength up to 1962; however, the year by year correlation of the two CPUE indices with each other was not significant. A similar correlation between cohort analysis estimates was significant, however. Both sets of cohort analysis estimates show a gradual decline in female stock size during the 1950's, and a leveling out at a lower level in the 1960's. Catch per unit effort indicates that stock size has increased in the 1970's. These trends in stock size seem to lag behind parallel trends in recruitment. Surplus production plots based on both CPUE and cohort analysis indicate that slightly higher yields are possible with increased effort. For English sole, the two sets of CPUE indices are highly correlated with each other. They both show extraordinary recruitment success for the 1961 year class, but no long-term upward or downward trends in recruitment. Female stock size increased when the 1961 year class was recruited, and has since decreased. The discrepancy between the two indices of Dover sole CPUE may be due to unusable effort data. The difficulties seem to be due to fluctuating market demand and the assignment of effort by species in a multispecies fishery. We feel, therefore, that changes in year-class strength of Dover sole are better determined by cohort analysis than by CPUE. For English sole, however, CPUE seem to be as reliable as cohort analysis, apparently because the greater desirability, shallower distribution, and behavior of English sole make the effort figure more valid.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<35:ACOCAA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

We examined relationships between cohort strengths of Dover sole (Microstomus pacificus) and English sole (Parophrys vetulus) off the Columbia River and variables that could hypothetically influence spawning success or survival. These variables included measures of spawning capacity, monthly means of oceanographic and Columbia River factors, and measurements of short-term weather variability. For Dover sole, spawning capacity was not significantly related to cohort strength. A correlation model incorporating two oceanographic factors, upwelling in early summer and offshore divergence the next winter, explained 65% of the cohort strength variation. Upwelling may have influenced food availability following yolk sac absorption, and divergence may have influenced the location of larval settling. For English sole, factors that had unusual values coincident with the unusually large 1961 cohort were not well correlated with the strengths of the other cohorts. Unique weather variability in the winter of 1960–1961, characterized by high storm frequency but low average wind speed, may have contributed to the 1961 success by stimulating plankton production. For the other cohorts, early fall (prespawning) values of up-welling, barometric pressure, and sea surface temperature showed significant correlation with cohort strength and accounted for 84% of cohort strength variability. During upwelling, these three factors were associated with bottom temperature; therefore, we propose that colder bottom temperatures, which may have delayed spawning or improved egg condition, were directly linked to stronger cohorts.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<54:EACSOD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The location of adult Pacific herring (Clupea harengus pallasi) near Auke Bay, Lynn Canal, Alaska, varied by depth and geographic area over 24 successive months during 1973–1975. From June through September, schools concentrated at 5- to 37-m depths where zooplankton was abundant and moderate currents were present in a stratified water column. The schools migrated from this area to wintering grounds in October when windstorms and sinking of cooling surface waters broke up stratification, and daylight and food abundance declined drastically. The schools remained near bottom in the deeper parts of the wintering grounds at 52-to 85-m depths into February or March when day length had increased, but temperatures and food abundance remained low. At this time the herring left the wintering grounds and moved up Lynn Canal to areas near spawning beaches. Pacific herring remained in these areas until water temperatures increased and plankton blooms appeared in late April and May at which time the fish moved into the shallows and spawned. By early summer the schools gradually concentrated again on the main feeding grounds.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<71:SDAEOP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Pink salmon, Oncorhynchus gorbuscha, eggs were collected from early-run and late-run spawners at Auke Creek, Alaska, and reared separately in a hatchery in deep-gravel incubators. Both groups of fry were marked the day after emergence, then released, unfed, to complete downstream migration. Early hatchery fry migrated downstream about 35 days ahead of late hatchery fry and about 55 days ahead of fry naturally hatched in Auke Creek. Hatchery fry developed faster than wild fry because hatchery water was warmer than Auke Creek water during egg incubation. Early hatchery fry had an average ocean life of 515 days and a marine survival of 0.17%; late hatchery fry had an average ocean life of 513 days and a marine survival of 1.46%. Low water temperatures experienced by early fry when they entered the estuary probably slowed their growth and made them more vulnerable to predators.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<79:MSOPSF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The spawning season of Gila trout, Salmo gilae Miller, in three streams in the Gila National Forest, New Mexico, began in early April at the lowest elevation and continued through June at the highest elevation. Water temperature and stream flow interacted to induce spawning; however, the former was more important. Spawning commenced at water temperatures near 8 C. Redds were normally in 6–15-cm deep water, about a quarter of the stream width from one bank and within 5 m of cover. The substrate was predominantly gravel and small pebble (0.2–3.8 cm). Spawning fish selected redd sites based on depth of water and substrate rather than on water velocity. Redds ranged in area from less than 0.1 m2to nearly 2.0 m2and averaged 3–4 cm in structural depth. Normally a single fish or a pair of fish occupied a redd, but occupancy by three to four fish was common. Most spawning activity occurred between 1300 and 1600 hours. Fry (15–20 mm long) emerged in 8 to 10 weeks and inhabited riffle areas. Absence of fry from pools occupied by adults indicated that cannibalism may occur.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<83:SHABOG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In the central Columbia River, southeastern Washington, bridgelip suckers (Catostomus columbianus) were common in deep water with strong currents during daylight and moved into slower shallow water at night. Mean calculated fork lengths (FL) in millimeters at annulus formation were age I, 63; II, 148; III, 224; IV, 291; V, 335; VI, 36I; VII, 387; VIII, 401; IX, 408. Back-calculated lengths approximated lengths at capture for respective ages. The length-weight (W) relationship for both sexes was logeW = - 12.65 + 3.25 logeFL. Both sexes reached maturity at about 350 mm FL and age VI. Peak spawning in all years occurred during May in water temperatures of 8–13 C. Breeding males and females both exhibited a narrow red lateral line stripe. Estimated egg numbers per mature female ranged frown 9,955 to 21,040. Bridgelip sucker diet was almost entirely periphyton, except fish smaller than 150 mm FL utilized mainly aquatic insect larvae and zooplankton. Variability of taxonomic characters caused some difficulty in distinguishing bridgelip suckers from sympatric largescale suckers (C. macrocheilus).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<92:LHOTBS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The possible existence of genetically distinct populations of spawning striped bass (Morone saxatilis) in the river systems of the upper Chesapeake Bay was investigated by a biochemical genetic approach. Samples of blood and liver from adult fish were obtained during the 1976 spawning runs from the Rappahannock (Virginia), Potomac, Choptank, Sassafras, Bohemia, and Elk rivers (Maryland), and Maryland waters of the Chesapeake and Delaware Canal. Samples were analyzed for frequency of occurrence of a polymorphic liver enzyme, glycerol-3-phosphate dehydrogenase, and variable serum proteins which were not correlated with age or sex. Multivariate and Bayesian analyses of these data indicate apparent genetic homogeneity of spawning bass within the upper Chesapeake Bay. If natal stream homing occurs, a sufficient number of wanderers may provide significant gene flow among river systems. The results suggest that long-term management of the fishery need not be totally on the basis of separate river units.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<99:AGHOSS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The structure of bluegill (Lepomis macrochirus) populations in natural Florida lakes was assessed from electromorphic and morphologic characters. Electrophoretically assayed allele frequencies are homogeneous within lakes and heterogeneous among lakes. Populations in two adjacent lakes connected by a short river are nearly identical. Several considerations indicate that even young-of-the-year bluegills are well mixed within subpopulations of these lakes, and that individual dispersal is important in maintaining intersubpopulation homogencity in allele frequency. This pattern of genetic differentiation contrasts with the pattern of heterogeneity observed in meristic counts for several morphological traits. At the microgeographic level, genetic homogeneity probably reflects a long-term history of bluegill movements within a lake, while within-lake morphological heterogeneity reflects the varied conditions during individual development to which incompletely isolated subpopulations are exposed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<108:GAMVOB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Juvenile rainbow trout (Salmo gairdneri) conditioned to traverse a 2.4-m-long channel to receive a food reward were subjected to in-transit thermal challenges. Conditioning was to a criterion that required 80% of the fish to leave the “home” area and reach the “reward” area within 2 minutes of release. Challenges were at successive 3 C increments above acclimation or the previous challenge temperature. Fish were first observed to delay their entrance into the intervening heated water at challenge temperatures of 12–15 C above acclimation. At each increment above 12–15 C over acclimation temperature, delay in transit increased; however, complete group inhibition was never achieved. Above their critical thermal maximum (CTM) the reward was achieved even at the expense of deaths among the achievers. Responses were the same whether fish were challenged individually or as groups. Fish exposed to their CTM without prior challenges at less stressful temperatures responded similarly to those receiving progressively greater challenges.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<116:IOTCOC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor