摘要:

The nature of new management strategies can be summarized in three main points. First, the age of simplicity is over, whether in the use of simple objectives like maximum sustainable yield or of simple single-species, constant-environment population models. Second, if there is any simple solution, it lies in taking management action very much earlier in the development of a fishery than has been the case before now. A formula is suggested for the appropriate licence fee for new entrants that might achieve this. Third, scientists will have to provide managers with much more detailed advice, giving predictions of the effects of different management actions, and the range of possible outcomes, which take account of uncertainties, as of environmental effects, or of the stock-recruitment relation. This will require increased research effort.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<1:FM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

To estimate the growth rate of the Atlantic croaker 113,670 juveniles were marked and released between 23 January and 23 March 1975. The experiment was divided into five tests; in each, the fish were marked with a different fluorescent pigment. Recapture efforts produced 110 usable returns. Individual croakers appear to have had an average maximum stay of 1.8 months in the nursery. Growth rate was estimated by the regression of length of recaptured juveniles on time; estimates ranged from 0.51 to 0.99 mm/day, all of which were considerably higher than most estimates in the literature. There was a trend of increasing growth rate through the five tests. Length frequencies of 159,381 croakers taken in a trap at the study area outlet could not be interpreted in a reliable manner for growth rate estimates. Future attempts to estimate young-of-the-year croaker growth rates should use methods other than length frequency.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<12:GROMJA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Age and growth data are presented on 380 spotted bass, Micropterus punctulatus, collected between June 1970 and July 1972 from Lake Fort Smith, Arkansas. Annuli were formed from late May through July; young spotted bass formed annuli earlier and during a shorter period of time than older individuals. Growth of males and females was similar and generally slower than that reported from other waters. The most active period of annual growth was initiated later and was of shorter duration in older fish. Growth, according to von Bertalanffy's equation, was best expressed as Lt= 350 [1 - e-0.511(t-0.330)], where L is total length in mm and t is age in yr. Maximum attainable length (L∞) was calculated to be 350 mm and 6.2 yr would be required to reach 95% of this length.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<21:AAGOSB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Stolothrissa tanganicae, an endemic clupeid of Lake Tanganyika (East Africa), dominates ring-net and traditional fisheries in most years, cycling from a low in catches in the first half of the year to high abundance in the latter half. From fish sampled in the ring-net fishery and from total catches of Stolothrissa we developed length frequencies by month, assessed monthly growth from modal lengths, and used Ford-Walford plots to assess a yon Bertalanffy growth constant k of 0.21 and maximum length (L∞) of 90 mm. From a length-frequency distribution, calculated monthly age frequencies, and a calculated age frequency in the catch, instantaneous mortality (Z) = 0.43 per month. Peak spawning in Zambia to the south takes place August-December, and from our data on monthly age-class contributions and published sources we concluded that the peak spawning period for Stolothrissa occurs January through April in the northern part of the lake, although recruits of other time origin may appear. A similar lag in biomass increase is probably adapted to timing of wind-induced nutrient upwelling and plankton production.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<26:GAMOST>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Patterns of diel feeding chronology, rate of gastric evacuation, daily ration, and prey selectivity were determined by season and by fish length groups for Lake Washington juvenile sockeye salmon. In summer and fall, sockeye fed intensely during the afternoon through dusk. During the winter a high percentage of the population did not feed. Those fish that fed did so at a much lower rate than observed in summer and fall. No feeding occurred in the hours of darkness at any time of the year. Rates of gastric evacuation decreased with fish body size and increased with water temperature. The daily meal (total intake) generally increased while the daily ration decreased (daily meal/fish body weight) with increasing body size. During the winter the daily meal and daily ration were considerably lower than those observed in the summer and fall. Juvenile sockeye salmon in Lake Washington showed size-selective predation that had marked seasonal trends as well as marked trends among fish size groups. These patterns suggested that sockeye optimally forage by ignoring small zooplankton forms upon encounter.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<36:DFCROG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Larval fish drift in the rocky-bottomed Susquehanna River (northeastern Pennsylvania) was investigated during 1974-1975. Near SSES (Susquehanna Steam Electric Station) at least 18 species of drifting larvae were collected by nets mounted on a stationary boat or by pumping. Maximum densities of 15.4 and 27.1 larvae/10 m3were found in June 1974 and 1975, respectively. Quillback, Carpiodes cyprinus (56%), minnows (25%), and carp, Cyprinus carpio (14% of the total) were the most abundant larvae caught in 1974 by pumping. The few larvae that drifted during the day were mostly near the bottom. Large numbers of quillback, white sucker (Catostomus commersoni), shorthead redhorse (Moxostoma macrolepidotum), and tessellated darter (Etheostoma olmstedi) larvae drifted near the river surface at night. Drift was maximum at about 2400 h. Overall, the day/night drift ratio was 1/3.8.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<46:LFDIAL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Eggs and larvae of the rainbow smelt, Osmerus mordax, were reared in the laboratory to 7.4 mm total length. Larger sizes were collected by plankton net from Lake Erie, Lake Ontario, and Cayuga Lake, New York. Manually stripped eggs were adhesive and demersal with a granular, yellow yolk. Egg diameter after fertilization and water hardening was 1.0 mm. The majority of eggs hatched between 183 and 195 h after fertilization at an average water temperature of 16.5 C. Average length of larvae at 195 h was 5.6 mm. Yolk absorption was complete at 6.4 mm. Pectoral fin development began before hatching. The dorsal, anal, and caudal fin rays began development at approximately 14 mm. The pelvic fins budded between 17 and 20 mm. All fin rays were complete at 36 mm. The adipose fin was complete at 29 mm. Separation of rainbow smelt from alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) was accomplished using yolk sac position, preanal and postanal myomeres, and snout-to-vent length as a percentage of total length.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<56:IOELAJ>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Laboratory studies assessed the effects of gradual and rapid decreases in temperature on 9-14-cm long threadfin shad collected from a tributary of the Tennessee River. Fish acclimated to 15 C and exposed to temperatures cooling 1 C each 72 hours decreased in feeding activity and schooled less compactly beginning at 9 C. At lower temperatures they lost orientation and were insensitive to external stimuli, and none survived exposure to 4 C. Threadfin shad exposed to sudden cooling (2 to 5 C decreases in 4 hours) lost equilibrium in proportion to the magnitude of temperature decrease if minima of 4 to 6 C were reached. Cold-shocked fish that had lost equilibrium for 0.2, 30, and 90 minutes before being returned to warmer water experienced mortalities of 32, 79, and 94%, respectively.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<63:EOLTOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

The fish faunas above and below Canyon Reservoir, Comal County, Texas, were surveyed to determine the effect of the impoundment upon the downstream community. Although 22 species were found above the reservoir, only 18 species were taken in the area downstream from the dam. Comparisons with pre-impoundment surveys of this area, taken a quarter century ago, indicate that seven species, which were once present in the downstream area, are now absent. Species diversity indices demonstrate reduced diversity below the impoundment. Changes in downstream water quality, especially water temperatures, due to hypolimnion water releases, seem to be the most likely causal factors associated with this disruption of the natural stream community.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<71:TEOHRR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A combined field and laboratory study was conducted to determine the avoidance reactions of blue crabs (Callinectes sapidus) to highly colored, acidic runoff from clear-cut timber areas above a productive north Florida estuary.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1978)107<78:FALARB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor