摘要:

Several strains of hatchery-reared brook trout, Salvelinus fontinalis (Mitchill), were exposed to low pH in the laboratory (sulfuric acid solutions) and in the field (mine acid polluted waters). Wild brook trout were also used in some field tests. Tests were both acute and chronic (up to 2 mo). Pronounced strain differences in survival ability were detected among embryonic, juvenile, and adult brook trout in laboratory tests, and among juvenile brook trout in field tests. However, in one case a strain difference in resistance times detected in field tests was not evident in several laboratory studies. A single selection of NYSV strain brook trout for high resistance to sulfuric acid solutions did not yield F1progeny of greater resistance. Prior exposure to nonlethal acidic conditions also did not enhance resistance of brook trout. In some cases, the fish actually became more sensitive to the low test pH after such a prior exposure. Fish had longer resistance times in sulfuric acid solutions and in mine acid polluted water if they were held previously in, respectively, pH 8 laboratory water, or nonacidic field environments. Wild brook trout survived longer at lethal field pH levels than hatchery fish which were tested immediately upon transport from the hatchery; there was no difference if the hatchery fish were held, prior to testing, in nonacidic field environments. Development of embryonic brook trout was delayed in sulfuric acid solutions of low pH. The time to loss of equilibrium at low pH was well correlated with total survival time. Fish removed at the time of equilibrium loss (in pH 2.75 and 3.25) did not recover when placed in pH 8 water. The rate of net sodium loss (in μmol/100 g˙h or μmol/h) at low pH was inversely correlated with the resistance times of brook trout. Fish had shorter resistance times in mine acid waters than in laboratory sulfuric acid solutions of comparable pH. Larger and older fish tended to survive longer although size was not strongly correlated with resistance times within narrow size categories of equal age fish. There was no difference between the sexes in survival times at low pH. The most important factors in enhancement of acid resistance in hatchery brook trout were the hereditary resistance of a given strain and the acclimation of fish to nonacidic stream or laboratory conditions prior to acid exposure. The establishment by selection within strains of one superior in acid tolerance will probably require many generations; screening for a tolerant strain from among extant strains may accomplish the goal more quickly.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<651:GAEFII>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Approximately two-thirds of the angling population of Erie County, New York was comprised of nonlicensed anglers. Anglers 9 to 15 yr of age, below the age minimum for license purchase, made up approximately 42% of the angling population and over 55% of the total days fished by Erie County anglers. Illegal nonlicensed anglers made up approximately 25% of the angling population. These figures suggest that fishery management policy-making based solely on license holders may exclude from consideration a substantial portion of the angling population of an area.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<678:PONAIR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Three hundred tagged largemouth bass (Micropterus salmoides) 14 to 29.5 cm long were divided into experimental groups of 100 fish which were designated as control, bait fishing, and artificial lure fishing. Since individuals were “known” by tag numbers, it was possible to test the hypotheses of (1) unequal vulnerability to angling among individuals and (2) hook avoidance learning. Results revealed that some conditioning or learning occurred among naive bass exposed to live bait angling for the first time. In the case of artificial lures and/or bass which were no longer naive, individuals appeared to have equal probability of capture and seemingly struck at random.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<682:SBOTLB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Two types of fish attractors, one made from vitrified clay pipes and the other from cement blocks and brush, were investigated in Lake Tohopekaliga, Florida. Electrofishing, creel census, and experimental fishing were used to evaluate the effectiveness of attractors in concentrating fish and enhancing fishing success. Both attractors produced significantly higher fishing success than did control areas and were generally superior to the average fishing success elsewhere in the lake. Brush-block attractors yielded a slightly higher success rate than the pipe attractors. Fishing success at attractor sites was highest during the first year after installation. The lower fishing success in subsequent years appeared to have been at least partially the result of a lake level drawdown which temporarily reduced the standing crop of fish and stimulated expansion of the littoral zone into deeper areas which had been devoid of plants. Soybean meal was found to be a supplemental fish attractant which increased fishing success at attractor sites where catch rates had diminished.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<689:TTOFAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Northern pike (Esox lucius) from eastern Lake Ontario were sampled with gill nets and trap nets in 1972-1973. Fish of age-groups IV, V, and VI were predominant in the catch. Although males were slightly longer after the 1st yr of life, females gained a 25-mm advantage in the 2nd yr and a 30-mm advantage in the 3rd yr. In later years, the increments of growth of males and females were similar. All males were mature after 2 yr and females after 3 yr. The stomachs of northern pike contained only fish; the alewife (Alosa pseudoharengus) was the principal forage species consumed. Electivity indexes for alewives, white perch (Morone americana), and yellow perch (Perca flavescens), the three most common species in the diet, indicated a positive selection for alewives that increased from June to October during a period when the relative abundance of alewives steadily decreased.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<696:AGAFON>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Atlantic salmon parr and brook trout were observed in stream tanks at the Matamek Research Station, Quebec. In the autumn, at 10 C Atlantic salmon parr began sheltering in rubble, and at 9 C the majority had disappeared into hiding. Brook trout also had this tendency to hide at cold temperatures, but not as strongly as the salmon. In slow water flows (<5 cm/s), Atlantic salmon parr tended to hide in the rubble substrate at any temperature, and aggression decreased. In both slow and faster water velocities during summer and autumn the commonest agonistic act by Atlantic salmon parr was “charge and chase”. Brook trout in July showed “nip” as the commonest agonistic act, but in September and October “approach” and “charge and chase” were more common, possibly due to aggression associated with spawning. Shade was attractive to both species in shallow water, but given the choice of a shallow (30 cm) tank with a shade cover, and a deeper (50 cm) tank with no shade, the majority of brook trout and Atlantic salmon selected the deeper tank. In one experiment in a shallow-water tank, turbulent water surface was more attractive to Atlantic salmon parr than shade.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<703:TBOJAS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The food habits of four species of sunfish, Lepomis macrochirus, L. microlophus, L. punctatus, and L. gulosus were studied in the Lake Pontchartrain estuary. Forty estuarine food items were identified from stomach samples. Although the food items were different from those of Lepomis spp. in fresh water, specific feeding patterns in regard to prey size and space partitioning were comparable. A discriminant functions analysis was used to objectively compare specific differences in stomach content data. Differences in discriminant function scores appeared to be due to interspecific feeding niche segregation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<713:ADFAOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The life history of the finescale dace, Chrosomus neogaeus, was studied in Itasca Park, Minnesota, during 1969-1971. The breeding season extended from late April through May. The more numerous males pursued females at the spawning sites; egg deposition occurred during an embrace under submerged logs and brush piles. Fecundity can be described by the equation Y = 62.59X − 1,764, where Y is the number of eggs, and × is the standard length (SL). Both sexes reached sexual maturity at age I. After sexual maturity, females grew faster (Y = 9.01X + 30.0) than males (Y = 6.20X + 36.0), where Y is standard length in millimeters, and × is the age in years. The largest female captured was 85 mm SL (age-class VI); the largest male was 67 mm SL (age-class V).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<720:RAAGOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Selective removal of grass carp was attempted in an 80-hectare Florida lake by means of a 0.1-mg/liter treatment of rotenone. A mark-recapture procedure was used to obtain a population estimate. Prior to the lake treatment, a field bioassay conducted in large polyethylene bags containing lake water and suspended in the lake, revealed that a 0.1-mg/liter concentration of rotenone killed grass carp but had little effect on sport fish. Fish collected from block nets set within the lake revealed lake-wide rotenone treatment removed more than half of the threadfin shad (Dorosoma petenense), grass carp, and golden shiners less than 100 mm. Appreciable numbers (20-50%) of largemouth bass (Micropterus salmoides), lake chubsuckers (Erimyzon sucetta), larger golden shiners, and redear sunfish (Lepomis microlophus) less than 100 mm were affected. Larger redear sunfish, bluegill (Lepomis macrochirus), warmouth (Lepomis gulosus), and black crappie (Pomoxis nigromaculatus) were abundant within the lake, as shown by quantitative block net sampling; however, their mortality from the selective treatment was less than 20% for all size classes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<724:UOSROG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The maximum-likelihood estimation procedure described by Hasselblad is a statistical method applicable to estimates of population parameters in a mixture of normal distributions of component age-groups. The method was used to estimate mean length-at-age and percentage composition of the component age-groups in 10 collections of largemouth bass (Micropterus salmoides) for which age was determined by the scale method. Compared to fish aged by the scale method, the error of the estimates of mean length-at-age averaged 3.2%. About one-third of the 31 frequency distributions, and six of seven distributions with more than 100 fish, deviated significantly from that of a normal distribution; many distributions exhibited skewness and kurtosis. However, the general failure of the samples to fit characteristics of the normal curve did not greatly influence accuracy in estimating mean length. The average error of the estimates of percentage composition by age was 28%; the magnitude of this error was related to the degree of asymmetry and a large standard deviation of length. The latter was apparently related to a prolonged and disjunct spawning season which produced multimodal distributions within each age-group.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<730:EOAMEF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor