摘要:

Seven genera—Brachymystax,Acantholingua,Salmothymus,Hucho,Salvelinus,Salmo, andOncorhynchus—make up the living Salmoninae. Relationships of 33 extant and 4 fossil salmonid species and subspecies were studied on the basis of 119 characters analyzed by parsimony algorithms. Twelve equally parsimonious trees each requiring 253 steps were calculated. Monophyly of recognized genera is consistent with all 12 estimates. The earliest branch of the family Salmonidae is the subfamily Coregoninae. Its sister group is the clade including the Thymallinae and Salmoninae. Within the Salmoninae,Eosalmo, from the Eocene of British Columbia, is the sister group of all living genera, as previously shown by Mark Wilson. The living Asian speciesBrachymystax lenokis the sister species of all other living Salmoninae, as documented by Carroll Norden. Three species of archaic trouts from the Mediterranean area—Acantholingua ohridana,Salmothymus obtusirostris, andSalmothymus(Platysalmo)platycephalus—branch off afterBrachymystaxbut before diversification of all other salmonines.Platysalmo platycephalusBehnke is the sister species ofSalmothymus obtusirostrisand is placed inSalmothymus. The clade beyond the archaic trouts includes four genera in two clades: (1)HuchoplusSalvelinusand (2)SalmoplusOncorhynchus. The Atlantic trouts and salmons are a monophyletic group,Salmo, and the Pacific trouts and salmons are a monophyletic group,Oncorhynchus. The terms “trout” and “salmon” refer roughly to life history modes, not to phylogenetic relationships. Morphological and mitochondrial DNA data disagree regarding the relationship ofOncorhynchus clarki(cutthroat trout) toOncorhynchus mykiss(rainbow, California golden, and redband trouts) and the relationship ofOncorhynchus gorbuscha(pink salmon) toOncorhynchus keta(chum salmon). Parsimony analysis suggests thatOncorhynchus mykissis the sister of the Pacific salmon, not ofO. clarki, thoughO. clarkiandO. mykisshybridize,Oncorhynchus gorbuschais the sister species ofO. nerka(sockeye salmon), not of keta, thoughO. gorbuschaandO. ketahybridize. Mitochondrial DNA is interpreted as having been transferred by introgression betweenO. gorbuschaandO. keta, providing misleading evidence of relationship. Fossil species ofOncorhynchusdocument a minimum age of 6 million years for the modern species of Pacific trouts and salmons.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0001:POTPTA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

High stocking or recruitment rates of juvenile fish can result in growth rate depression, so fisheries managers may need to consider a trade-off between producing large numbers or large sizes of fish. Analysis of food production, feeding, and bioenergetics of growth leads to a model for predicting such density-dependent growth depression. This model can be expressed as a simple hyperbolic equation whose parameters can be estimated from field data on maximum growth rates and growth depressions under controlled field conditions, If feeding rates are assumed proportional to the square of body length, the equation leads to a von Bertalanffy growth curve with only the asymptotic size varying with density, When all sizes of fish consume the same foods, the model predicts that increasing density will lead to parallel Ford–Walford plots with intercepts that are inversely proportional to density, A key complication regards partitioning of the food resource by small and large fish, which may lead to differential growth suppression (competitive asymmetry) among age- or size-classes. We predict that the differential suppression should lead to changes in the slopes of Walford plots with changes in density, and we suggest measuring these changes with simple field experiments involving factorial combinations of low and high densities of juvenile and larger fish. However, such experiments are unlikely to provide adequate parameter estimates for more detailed models that hypothesize allometric effects on both partitioning of food resources and metabolism in size-structured fish populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0034:DDGACA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We quantified annual consumption and annual production of the principal predatory fishes (smallmouth bassMicropterus dolomieu, rock bassAmbloplites rupestris, and flathead catfishPylodictis olivaris) in a 62-hectare pool of the New River, West Virginia, to evaluate the potential for competition among these species and people for crayfish (Cambarus sciotensis,Orconectes sanbornii sanbornii, andOrconectes virilis) and hellgrammite (Corydalus cornutus) resources. Production of smallmouth bass (3.21 g·m−2·year−1), rock bass (2.00 g·m−2·year−1), and flathead catfish (0.56 g·m−2·year−1) was supported primarily by aquatic insects (age-0 and age-1 fishes) and crayfish (age-2 and older fishes). Hellgrammites were rarely eaten due to their secretive nature, and prey fishes were less numerous than crayfish in the diets and the environment. Diet overlap among the three species was relatively high (Schoener's overlap index = 0.74–0.93); species composition and sizes of crayfish eaten by the three fish species were similar. Smallmouth bass, rock bass, and flathead catfish consumed 35, 31, and 10% of the annual production of age-1 and age-2 crayfish and less than 1, 13, and 1% of the annual production of age-1 and age-2 hellgrammites. A bait fishery harvested an additional 5% of crayfish production and 8% of hellgrammite production. Peak consumption by cohorts of all three fish species occurred in August and September and was a function of survivorship, increasing individual fish size, and temperature-controlled energetic demand. Seasonal patterns of cohort production and biomass mimicked trends in consumption. Peak fish production rates in late September were a function of survivorship, increasing individual fish size, and high rates of prey consumption. Cohort biomass accretion exceeded attrition from mortality during most of the growing season, peaking in October. Crayfish are critical prey for the smallmouth bass, rock bass, and flathead catfish populations in the New River. The sizes ofcrayfish eaten by these fishes and harvested by people, the extent of use of crayfish production by these fishes and people, the crayfish species composition in the diets of these fishes, the intensity of predation on crayfish in late summer, and diet overlap suggest that competition among New River fishes and people for the crayfish resource is intensive. Increases in bait harvest or efforts to improve the quality of New River sport fisheries would probably increase competition for the crayfish resource.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0046:TBOPOS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The health assessment index (HAI) is an extension and refinement of a previously published field necropsy system. The HAI is a quantitative index that allows statistical comparisons offish health among data sets. Index variables are assigned numerical values based on the degree of severity or damage incurred by an organ or tissue from environmental stressors. This approach has been used to evaluate the general health status offish populations in a wide range of reservoir types in the Tennessee River basin (North Carolina, Tennessee, Alabama, Kentucky), in Hartwell Reservoir (Georgia, South Carolina) that is contaminated by polychlorinated biphenyls, and in the Pigeon River (Tennessee, North Carolina) that receives effluents from a bleached kraft mill. The ability of the HAI to accurately characterize the health offish in these systems was evaluated by comparing this index to other types of fish health measures (contaminant, bioindicator, and reproductive analysis) made at the same time as the HAI. In all cases, the HAI demonstrated the same pattern offish health status between sites as did each of the other more sophisticated health assessment methods. The HAI has proven to be a simple and inexpensive means of rapidly assessing general fish health in field situations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0063:AQHAIF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Harvestable-size largemouth bassMicropterus salmoideswere collected from 53 Florida lakes to determine relationships between mercury concentration in fish and physical and chemical lake characteristics. Diverse lakes with a broad range of sizes (15–181,000 hectares), pH (3.6–9.1), and alkalinities (1.2–128 mg/L as CaCO3) were sampled. Total mercury concentrations in axial muscle of individual fish ranged from 0.04 to 2.04 μg/g wet weight and were positively correlated with fish age (strongest correlation) and size. There was no difference in the rate of mercury accumulation by age between the sexes, even though females grew faster. Chemical characteristics oflakes strongly influenced the bioaccumulation ofmercury in largemouth bass. Mercury concentrations, standardized to age-3 fish for comparison among lakes, ranged from 0.04 to 1.53 μg/g and were negatively correlated with alkalinity, calcium, chlorophylla, conductance, magnesium, pH, total hardness, total nitrogen, and total phosphorus. No significant correlations were observed between the standardized fish mercury concentration and lake color, secchi transparency, tannic acid, or surface area. Linear regression revealed that pH accounted for 41% of the variation in the standardized fish mercury concentration. Multiple regression revealed that chlorophyllaand alkalinity accounted for 45% of the variation in the standardized fish mercury concentration. Mercury concentrations were significantly higher in lakes with either pH less than 7, alkalinity less than 20 mg/L as CaCO3, or chlorophyllaless than 10 μg/L.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0074:IOWCOM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Fecundity, ovary weight, and egg weights, adjusted for fish length, of anadromous alewivesAlosa pseudoharengusand blueback herringA. aestivalisdiffered among some of four Maritime province rivers. Fecundity was poorly predicted by age. Spawning history (number of previous spawnings) did not affect fecundity and “fecundal senility” was not observed. Fecundity was usually higher for blueback herring than for similarly sized alewives. Reproductive condition (gonadosomatic index) of mature fish differed among rivers for both species. The time of sample collection influenced gonadosomatic index values for blueback herring but not for alewives. Gonadosomatic index values of alewives and blueback herring were uncorrelated with an index of distance upstream × elevation of the sampling site. Two major egg size-groups occurred in mature ovaries of both species. The largest egg size-group consisted of eggs ripening for spawning; the smallest size-group was retained after spawning. Fertility, as a percent of total fecundity, ranged from 38% to 67% for alewives and 39% to 52% for blueback herring, depending upon the estimation method used. Egg weight decreased with increasing fecundity for both alewives and blueback herring. For fish of equal length, fecundity of both species decreased with increasing latitude, whereas egg weight increased for alewives and did not vary significantly for blueback herring. Ovary weights did not vary with latitude for either species. The occurrence of fertility rates substantially lower than total fecundity, of geographic clines in fecundity, and of differences between species in fecundity and egg weight are important for understanding the reproductive strategies of, and for managing, alewives and blueback herring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0085:FOAAAB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We analyzed experimental gill-net catches of spotted seatroutCynoscion nebulosusat 28 stations in various estuarine habitats over 3 years (1988–1990). Cluster analysis indicated that the 28 stations reduced to three “natural” groupings representing salinity zones that correspond to upper (oligohaline, 0–9‰), intermediate (mesohaline, 10–14‰), and lower (polyhaline, 15–30‰) estuarine zones. Principal components analysis applied to log-transformed gill-net catches yielded a two-factor model that explained 78% of the variation in the data; factors were interpreted as recruit size (females smaller than 31 cm in total length and males smaller than 26 cm) and spawner size (females larger than 31 cm and males larger than 26 cm). Both recruit and spawner models were highly significant (P< 0.0001), and the zone-by-season interaction accounted for the greatest proportion of the variation in the models (P< 0.0001). Abundances of recruit and spawner spotted seatrout were greatest in the lower estuarine zone (15–30‰) during the spawning season (May–August), when both recruit and spawner abundances had high positive correlations with salinity (P< 0.01). After the spawning season (September–December), spawners were uniformly distributed over all estuarine zones, whereas recruits were significantly more abundant (P< 0.01) in the upper estuarine zone (0–9‰). During this time, recruit spotted seatrout abundance showed a high negative correlation with salinity (P< 0.01).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0099:SSDIFC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

To determine how moonlight and daylight affect hydroacoustic estimates of fish abundance, we used a dual-beam transducer and echo integration to survey pelagic fish (primarily Bonneville ciscoesProsopium gemmifer) in Bear Lake, Utah and Idaho. During the new moon, the fish were dispersed (not schooling) below the thermocline, chiefly at the depths of 10–20 m. At full moon, they were dispersed but much closer to the bottom, where they were difficult to detect. Acoustic estimates offish density and biomass during full moons were approximately 50% of values derived during new moons. A diel survey during a new moon indicated that fish were widely dispersed in the water column at night, but formed schools at dawn. Our study indicated that light conditions must be standardized to insure consistent and comparable population estimates of some pelagic fishes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0112:EOMADO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Apache troutOncorhynchus apachehas become threatened through hybridization with introduced nonnative trouts, among other reasons. We used 10 isozyme locus polymorphisms, which were in the aggregate diagnostic for discrimination of alleles of Apache trout, rainbow troutOncorhynchus mykiss, and cutthroat troutOncorhynchus clarki, to assess extent and directionality of interspecific hybridization in 645 individuals from 31 wild populations within the historical range of Apache trout. Only 11 potentially unhybridized populations of Apache trout were found. Rainbow trout introgression was documented in 19 of the 31 populations, including at least two in which all individuals sampled were hybrids. In four of these introgressed populations, hybridization between cutthroat trout and Apache trout was detected; at two of these localities individuals with alleles from all three species were sampled. Apache-cutthroat hybrids were found at one locality where no rainbow trout alleles were sampled. In 19 of the 20 hybridized populations sampled, a trend of backcrossing toward Apache trout was evidenced. No pure rainbow trout or cutthroat trout were found in the population samples. Because of the extensive hybridization present, it was not possible to estimate the genetic variability extant in the Apache trout genome; only one of seven alleles detected exclusively in hybridized populations could be confidently assigned to a species of origin (rainbow trout). Apache trout recovery efforts will be confounded due to the variable conditions among populations with respect to introgression, habitat deterioration, and barriers to rainbow trout immigration.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0121:IAACAR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We investigated the effect of parental body length on the swim-up date and length of larval largemouth bassMicropterus salmoidesin experimental ponds, and the effect of swim-up date on larval length, growth, and survival in three reservoirs. Swim-up date was estimated from counts of daily growth rings in otoliths. Larvae spawned by larger adults had significantly more daily rings on the same sampling date than larvae of smaller parents, indicating that larger adults spawned earlier. Length of larvae at swim-up was independent of parental length, indicating that larger adults did not produce larger larvae. Positive correlations between larval age and total length indicated that initial length advantages resulting from earlier swim-up dates persisted. Fish that swam up earlier in the year grew faster. Differential survival in relation to time of swim-up could not be detected by midsummer, but differential growth rates might lead to differential survival late in the year. Our results suggest that protecting the larger adult largemouth bass may advance the average time of spawning in a population, thus increasing the length attained by young at the end of their first year and possibly their recruitment to age l .

ISSN:0002-8487    

DOI:10.1577/1548-8659(1993)122<0131:EGASOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor