ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<443:ISOTEL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The argument is made that early life history studies of fishes often seem to receive less recognition and support than their real potential would merit. I believe that the state of the art in these studies has advanced to the stage where efforts to improve their image could be usefully promoted. It is suggested that their promotion could be facilitated by their identification with saleable goals relating to resource problems of regional or national concern. Three major goals for these studies are seen to involve recruitment, culture, and water quality. A number of interdisciplinary activities that are supported by or contribute to these goals are listed. The question of publication also is considered. There appear to be adequate repository journals for studies in the domains of culture and water quality, but not in recruitment biology. The suggestion follows that there is need for recognition of the associations between the three domains, embodied in early life history studies, in the format of some current journals; indeed, there may even be a place in the literature for a journal of recruitment biology. Finally, the development of a compendium of basic early life history data is proposed, constructed around a carefully defined format based on the common activities contributing to the three related research domains and their indicated goals.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<445:APVOEL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The gulf menhaden commercial fishery in the Gulf of Mexico is the largest by weight in the United States. Spawning takes place on the continental shelf during fall and winter and the pelagic larvae are transported into estuarine nursery areas. Quantitative information on a transport mechanism had previously been lacking. Knowledge of the coupling between continental shelf and estuaries is necessary to understand the causes of high natural variability in estuarine recruitment and to develop and evaluate spawner-recruit and environment-survival relationships. Analysis of a variety of biological and physical data led to the development of a testable transport hypothesis. The hypothesis suggests that west-northwest longshore advection within the horizontally stratified coastal boundary layer is the primary mechanism transporting gulf menhaden larvae to the Calcasieu River estuary, the major estuarine system in western Louisiana.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<452:TOLGMB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The transport of plaice larvae from the open sea towards shallow, mainly inshore, nursery areas along the North Sea coast was studied for 5 years in the Easter Scheldt and the Wadden Sea. Metamorphosing larvae (stages 4 and 5) entered the nursery areas in March and April. Larva density was significantly correlated with the density of 0-group plaice at the end of the following summer. Significant factors determining the larval densities were date of sampling, location, tide, depth, and did period. Larvae usually were most abundant in the bottom stratum, but during nighttime flood tides they moved into midwater and surface strata. Flood catches exceeded the ebb catches of pelagic larvae for all stations. The results suggest that plaice larvae accomplish passive but selective horizontal transport by swimming up from the seabed during flood tides and remaining on the seabed during ebb tides.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<461:STTONS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The early life history of the red sea bream was investigated to elucidate the recruitment mechanism, as a biological basis for farming fisheries, in Shijiki Bay, southwestern Japan, during 1975–1983. Pelagic larvae, hatched during March-May in offshore spawning grounds, are transported by tidal currents and trapped by a circular current at the mouth of the bay. Larvae reach 10 mm total length about 30 d after hatching, when they begin to metamorphose into pelagic juveniles. The juveniles begin to migrate into the bay beyond the boundary area between the outer and inner water masses. This orientation seems to be closely related to their diel vertical migration. After immigration into the bay, juveniles become demersal. At this period, their main food organisms are the copepods Acartia clausi and A. steueri. Both prey species are contagiously concentrated near the bottom, and their densities increase towards the innermost part of the bay. This gradient of copepod distribution leads the early juveniles to the nursery ground, where gammaridean amphipods, the most important foods for demersal juveniles, are abundant.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<471:FATIMO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We analyzed ichthyoplankton data from six cruises off southwest Nova Scotia, spanning the spawning and early life history period (February-June), to determine the stage(s) at which the apparent failure of the 1983 haddock year class occurred. Egg production over the season did not differ significantly from that expected, but the abundance of larvae was 1–2 orders of magnitude lower than in recent years. Instantaneous egg mortality rates (M) calculated from catch curves were very high: 0.21–0.54 for the six cruises. The lowest egg mortality rates (M = 0.21–0.22) occurred during peak spawning (April), but no surviving larvae were obtained from this period, which indicates sharply increased mortality at or near the point of hatch. There appeared to be a weak relationship between wind displacement and diffusion rate of the egg mass, but drift rates were low, and wind speeds generally below average during the study period. Temperatures in the upper 50 m over the spawning ground, where the eggs predominantly occur, were in the normal range for haddock embryonic development throughout the study period. The dominant invertebrate predator encountered on the cruises was the ctenophore Pleurobrachia pileus, but calculations indicate it did not contribute significantly to egg mortality. Our study does not support the hypothesis that there is a single critical period in the early life history of haddock. The failure of the 1983 Browns Bank year class seems to have been determined prior to the period of first-feeding by larvae and to have been compounded over several developmental stages.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<478:AOAAYF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Microstructural growth increments in otoliths of autumn-spawned, larval Atlantic herring from the Sheepscot River estuary of western Maine and Sullivan Harbor of eastern Maine provided estimates of mortality, growth, or transport times (or combinations of these) for 19 cohorts in 1980–1982. Mortality within seven cohorts averaged 2%/d (range, 0.7–3.1%/d). Growth (12 cohorts) averaged 0.199 mm/d (0.123–0.270). Transport times of larvae hatched on the spawning ground of eastern Maine and captured in the harbor and estuary (8 cohorts) averaged 16.5 d (5–35 d). Estimates of mortalities agreed (P > 0.05) with those from multicohorts obtained in the 1960s and 1970s (0.4–3.2%/d). Among the cohorts, extremes of larval growth differed significantly (P < 0.05), but most were similar and showed a weak trend toward slower growth in 1980–1982. No difference in growth (P > 0.05) was noted between larvae of cohorts spawned relatively early and those of a cohort spawned late. Larval mortality and growth appeared inversely correlated (P < 0.05) for seven cohorts. Variability in transport times was seven-fold, suggesting a wide dispersal of larval cohorts throughout the coastal water while in transit from the spawning grounds to inshore areas of retention. Possibly, different members of the same cohort from the eastern coastal spawning ground moved 95 km (straight-line distance) in 8 d to Sullivan Harbor and also 273 km to the Sheepscot estuary in 35 d. Although larval recruitment mechanisms are manifested inshore, it is suggested that such mechanisms are anticipated through cohort development in the coastal water.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<490:MGATOL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The stomach contents of 5,408 herring caught during North Sea trawl surveys in February 1980, 1982, and 1983 were analysed with a view of estimating predation mortalities exerted by the herring stock on plaice and cod eggs, based on the spatial distribution of size categories of herring and the numbers at age estimated from virtual population analysis. Predation on plaice and cod eggs was generally confined to the southern North Sea and only the younger age groups of herring (ages 2 and 3) consumed substantial numbers of fish eggs. Occasionally fish larvae (herring and plaice) were encountered. The estimated fraction consumed of the initial numbers of eggs produced varied from 0.7 to 1.9% for plaice and from 0.04 to 0.19% for cod. These estimates are necessarily crude and can only give a rough indication of the true predation mortalities. Although some effect of herring stock size on the level of recruitment of plaice might be expected, it is unlikely that the generally observed increase in recruitment to various demersal stocks in the 1970s could be entirely accounted for by a reduced predation on eggs by herring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<499:PBNSHC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The size of Atlantic cod eggs declines during the spawning season, and the potential effects of this on larval development were studied. Eggs from 12 females were artificially fertilized and incubated in separate aquaria. Egg diameter was correlated significantly (P < 0.05) with egg dry weight. The standard length of unfed larvae continued to increase a few days beyond yolk exhaustion, whereas the increase in muscle tissue (myotome height) reached its maximum at the time of yolk exhaustion. Egg dry weight was significantly correlated with larva dry weight, standard length, myotome height, and the size of the mouth gape. The ability of larvae to capture artemia nauplii was related to the size of their mouth gape, itself a function of larval size. Atlantic cod larvae from large eggs may survive the shift to exogenous feeding better than those from small eggs. Late-spawned Atlantic cod larvae may have a lower survival potential than those spawned earlier in the season.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<507:GDAFSO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Recruitment of Cape anchovy in South African waters has been strong and consistent for nearly 20 years, despite year-to-year variability in the physical marine environment. This suggests an element of density-dependent regulation in the population dynamics of this species. Cannibalism might be such a regulator, and laboratory experiments were conducted as a first step toward assessing the importance of cannibalism by larvae. Eggs and various sizes of larvae were added one at a time to tanks containing larger larvae and any approaches of potential predator and prey were observed. Some predator larvae between 15 and 35 mm standard length were capable of capturing and ingesting prey larvae as large as their mouth openings would permit, approaching half their own body length. Eggs and yolk-sac larvae without pigmented eyes were less readily detected, and therefore less likely ingested, than early eyed larvae. Predation efficiencies (proportions of prey detected, struck at, or ingested) increased with increasing predator size and tended to decrease with increasing prey size. Cannibalism was markedly reduced when predators were pre-fed copepods or when prey larvae were introduced at the same time as copepods. Thus, the potential exists for cannibalism among co-occurring Cape anchovy larvae of different sizes, its extent being modified by predator and prey length and availability of alternative prey.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1985)114<512:LAOCBL>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor