摘要:

Matched plantings of hatchery-reared yearling brook trout (Salvelinus fontinalis) and splake (Salvelinus namaycush × S. fontinalis) or brook trout and rainbow trout (Salmo gairdneri) were made in Little Minnow Lake for 6 yr prior to and 6 yr following the introduction of yellow perch (Perca flavescens). The mean return for each kilogram of fish planted was 3.3, 6.8, and 6.1 kg, respectively, for brook trout, splake, and rainbow trout in pre-perch years but after yellow perch became established the mean returns were 0.4, 0.9, and 0.8 kg, respectively, all less than the weight planted.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<505:TEOCWY>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

To evaluate hooking mortality of lake-angled landlocked Atlantic salmon (Salmo salar), angled and net-trapped (control) fish were held for 5 days after capture in each spring and fall for 4 yr. Angled fish suffered a significantly greater mortality than controls in both spring (P < 0.001) and fall (P < 0.05). Mortality of fall-angled salmon was significantly less than that of spring-angled fish (P < 0.01). No significant differences (P > 0.05) were found between hooking mortality of age II and III fish, nor between legal-sized (⩾356 mm, total length) and sublegal salmon. Most mortality occurred within 24 h of hooking. No significant differences (P > 0.05) were found between mortality caused by single- and treble-hook gears, nor between flies and lures. Mortality of gill-hooked fish was significantly greater (P < 0.001) than that of salmon hooked in the mouth area. No particular gear, hook, or lure type was more prone to hook fish in vital anatomical locations. Mortality of fish bleeding from hooking was significantly greater (P < 0.001) than that of nonbleeding fish. Hooking deaths (y) were predicted accurately from accumulated angler-hours (x) by the formula: y = 2.772 + 0.029x.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<518:HMOLLA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Physical conditioning at swimming speeds of 2 and 3 body lengths per second for periods up to 30 days increased critical swimming speed by as much as 15% over that found for unconditioned fish. Haemoglobin increased significantly with conditioning, suggesting an enhancement of aerobic capacity. Conditioning did not, in general, increase the production of lactate dehydrogenase in blood serum. Following periods of swimming at critical speeds, blood volume decreased in unconditioned bass but with conditioning remained relatively stable.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<523:CIBCAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The planar shape of fish scales may be quantified by a method of unrolling the digitized scale outlines and describing the resultant series by Fourier series. Each scale shape is defined by a vector of harmonic amplitude coefficients and phase angles. Each harmonic in the vector generates a shape component which can be reconstructed graphically. The contribution of each harmonic to the goodness-of-fit between the model shape and the observed scale shape is known. The method was successfully applied to discriminate stock samples of 5-yr-old male walleye (Stizostedion vitreum vitreum) from two locations in eastern Lake Erie.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<528:NMOQSS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Population dynamics of anadromous rainbow smelt, Osmerus mordax (Mitchill), in the Parker River estuary, Massachusetts, were investigated during the spring spawning runs of 1974 and 1975, and the winter recreational fishery of 1974-1975. Growth (in length) was greatest in the first year of life, and nearly ceased by age V. Avon Bertalanffy growth function fitted to the data (l = total length, mm; t = years) is: lt= 256.29[1 - e-0.6393(t + 0.0018)]. The length (L, total length, mm)/weight (W, g) regression is: log10W = −6.0315 + 3.3592 log10L. Parker River fish were partially recruited to the spawning population at age I and were probably fully recruited at age II. Total mortality was lower for females than males. Total annual mortality of adults averaged 72%. Fifty percent selection to the angling fishery occurred at 166 mm. Modeled values of fishing mortality that result in greatest yield per recruit to both the present angling fishery and a simulated dipnet fishery on the spawning grounds would probably be detrimental to future recruitment.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<535:PDOARS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The logistic surplus production model is applied to the lake trout (Salvelinus namaycush) fishery of district MS-4 in Lake Superior from 1929 to 1950. Comparison of the equilibrium stock production curve with observed yield and effort data indicates that the fishery became overexploited at about the same time that the sea lamprey first was observed in the lake. This was a period during which fishermen were moving to Lake Superior from the other lakes as lake trout stocks were collapsing as a result of sea lamprey predation. The sharp decline in lake trout yields from Lake Superior occurred about 10 yr later. Collapse of the lake trout stocks apparently was caused by sea lamprey predation on a population that was stressed by intensive exploitation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<543:AOTLTF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Longnose dace taken mainly during night hours over gravel-rock substrates in a surge zone of east-central Lake Michigan provided seasonal data on distribution, age, growth, maturity, fecundity, and food habits. Dominated by age-classes II and III, longnose dace entered surge-zone waters in mid-May for spawning and remained in small numbers through November. Peak spawning occurred during late June and early July. Egg production ranged from 870 to 9,953 eggs per female. Age 0 fish were taken in early August and reached a mean length of 42 mm by late October. Only a few yearlings (age I) spawned the following year; all fish were mature by age II. Major foods of adult fish were from terrestrial sources.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<550:LHOTLD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The predator Luciolates stappersi (Centropomidae) is an important component of the pelagic fishery in Lake Tanganyika, Burundi, and an effective competitor of man for the valuable stocks of endemic clupeid fish. Annual landings of Luciolates (400-1,200 metric tons) vary widely, but the average catch has declined only slightly during 20 yr of purse-seine fishing. The major seasonal catch occurs in January-April and includes predominantly mature fish; juveniles are taken year around but mainly in August-October. Adults mature at around 210 mm fork length, and the period of maximum gonad development is January-April. Eggs and fry are planktonic. Growth was not estimated reliably but length-frequency progressions suggest average rates of 5 mm/mo for fish smaller than 100 mm, and 9 mm/mo for larger fish. The maximum size of Luciolates is about 450 mm, but most mortality occurs by the time fish reach 350 mm. A cohort contributes to the fishery for 3-5 yr. Young fish eat zooplankton but after they grow past 130 mm they take clupeids almost exclusively. Form-and-function analysis helps characterize Luciolates as a swift predator. The species spends most of its life in the upper 30 m of offshore waters, and can be attracted to light sources. The Burundi population may recruit from outside territorial waters.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<557:BOLSIL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

From deck samples in 1974-1975 in the industrial fishery of Lake Tanganyika in Tanzania, we determined total catch, length frequencies, and sexual maturity of Luciolates stappersi. Bimodality developed in lengths of juveniles, but adult lengths formed single modes or very weak double modes. Monthly modal progressions of juveniles indicated growth series originating in March and December. Each year one age-group dominates the catch, becoming most abundant early in the calendar year, the reproductive season. After the spawning period, catches decline sharply, either from spawning-related mortality or behavior which makes the year class less vulnerable to exploitation. Adults grow at about 0.7 cm per month. Sexually ripe adults appeared in purse-seine catches year-round, but more females appeared in advanced maturity in November-February and August. Our data fit well with those from other studies of Luciolates, except that the latter suggest a longer life span.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<567:OOTBOL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Young-of-year largemouth bass in Clear Lake, California, switched from feeding largely on blue-gill (Lepomis macrochirus) to feeding largely on Mississippi silverside or on a mixture of prey species following the establishment of the silverside in the lake in 1967. Choice of prey, however, was influenced by relative abundance of the prey, the habitat occupied by the bass, time of day, and size of the bass. The bass usually switched to a predominantly fish diet at a smaller size when silversides were the main prey than when bluegill or Sacramento blackfish (Orthodon microlepidotus) were the main prey. The success of the introduction of small numbers of Florida largemouth bass into the lake in 1969-1971 was demonstrated by the presence of significant numbers of bass that could be classified as intergrades between Florida and northern largemouth bass (M.s. salmoides), the subspecies originally introduced into Clear Lake. No meaningful differences in the feeding habits or average lengths of the intergrades and “pure” northern bass were found.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<574:EOTIOM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor