摘要:

We constructed a computer simulation model to test several hypotheses about year-class formation of English soleParophrys vetulusoff the coast of Oregon. Rather than use the model to generate best-fit estimators of future recruitment, we sought to construct a model that can serve as a framework for studying mechanisms that may not always be dominant in their effect. The model was constructed from available information on the species' life history and coastal ocean environment. We investigated effects on year-class strength of relationships between (1) fecundity and temperature, (2) egg-hatch success and temperature, and (3) advective loss of larvae and wind. Hypotheses were translated into functional relationships and evaluated based on the correspondence between year-class strength estimated by cohort analysis and simulated with the model. The model was driven by time series of fishery and physical data. The final model accounted for 53% of the variance during 1960–1970 and emphasized the integration of several components consequential to recruitment: stock size and structure, fecundity, spawning seasonality, egg hatching success, and advection. These results weakened the concept of critical period because events before spawning and during the full pelagic stage were also very important. The variability in time of spawning was particularly consequential to year-class success. Spawning generally was adapted to periods of optimal temperatures for egg development and favorable larval advection; it was partly cued by increasing shelf temperatures coincident with onshore drift. Also, time of spawning may be adapted to periods of enhanced feeding success because it is likely that the major prey (Oikopleuraspp.) of English sole larvae are swept into the coastal zone during downwelling.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0101:ESOESR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The performance of two bottom-sampling trawls was evaluated under various rigging configurations and operating conditions. The trawls examined were a semiballoon shrimp trawl usually towed from a single warp and a high-rise trawl towed from two warps. The geometric performance (i.e., configuration of the trawl while in operation) of the full-scale nets was measured hydroacoustically in the field, and scale models were tested in a tow tank. For the shrimp trawl, wingspread increased significantly with increased bridle length but was not significantly affected by increased speed or current direction. Headrope opening decreased with increased towing speed and bridle length. For the high-rise trawl net, wingspread and headrope opening both decreased with increased speed. In contrast to the clear differences in geometric performance related to net design, rig, and operation, the analyses of catch data from Narragansett Bay, Rhode Island, were not definitive. The high-rise trawl captured significantly more total demersal fishes and winter flounderPseudopleuronectes americanusby weight than the shrimp trawl, but the two nets caught similar sizes of winter flounder. Catches of winter flounder in the shrimp trawl were significantly affected by towing speed and current direction; however, bridle length of the shrimp trawl did not affect these catches demonstrably. Towing speed and current direction did not significantly affect total catch, demersal fish catch, or pelagic fish catch.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0119:COTPOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Brood stock of critically endangered bonytailGila eleganswas obtained between 1976 and 1981 from Lake Mohave, Arizona-Nevada, and propagated by artificial means and by natural reproduction in ponds at Dexter National Fish Hatchery, New Mexico. Twenty-four naturally produced F2individuals were examined electrophoretically for soluble gene products of 45 loci. Six polymorphic loci were identified: aspartate aminotransferase (sAat-A), glucose-6-phosphate isomerase (Gpi-B), and phosphoglucomutase (Pgm-A) from skeletal muscle; esterase (Est-2) from brain; and catalase (Cat-1) and L-iditol dehydrogenase (Iddh-A) from liver. Electromorph distributions at each locus agreed with Hardy–Weinberg expectations. Hatchery bonytail had a lower mean level of heterozygosity than arroyo chubG. orcutti. However, direct-count heterozygosity for bonytail was comparable to mean values reported for other western North American cyprinids. Allozyme variation expressed by hatchery-produced bonytails suggested a genetically variable stock suitable for reintroductions into appropriate wild habitats.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0131:OOBSAA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A physiological basis for correlations among type of metabolism, behavior, and lifestyle is described for two early ontogenetic stages of coregonine fishes. Stage I extends from first feeding attempts until the end of metamorphosis, which usually occurs at a total length of 2–3 cm. Stage II extends through the juvenile period to a size of 8–10 cm. During the change from stage 1 to stage II, activities of several glycolytic and muscle enzymes increase severalfold. This increase in enzyme activities indicates a switch in major energy substrates from fatty and amino acids to glycogen. Prey selection data (prey ranked by size and mode of swimming), predator–prey reactive distance, and prey-handling time per unit energy return (profitability time) are given for coregonines in stages I and II. Results from studies of coregonine species from many different locations are incorporated into a deterministic model to estimate relationships between physical and biological environmental factors and fish growth. The growth rate peaks at a specific swimming speed, the optimum foraging speed. Simulation experiments demonstrate that optimum foraging speed increases exponentially as a function offish length and depends on density and type of prey. After further analysis of the relationship between mortality and growth rate, the bioenergetic data presented may facilitate the assessment of year-to-year variation in recruitment to the adult stock.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0138:ALFCOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The study of ontogeny yields two types of information of potential use for phylogenetic reconstruction: information about characters and about transformation among the states within characters. Transformational information is used to construct hypotheses of character state homology, polarity, and order. Character state order refers to the evolutionary connections among character states, whereas polarity refers to the direction of evolution along hypothesized connections (i.e., which character conditions are primitive and which are derived). Hypotheses of either character state order or polarity require assumptions about evolutionary processes and constrain phylogenetic construction. The use of ontogeny to infer phylogenetic order among character states requires the assumption that evolution modifies states one at a time, through addition or deletion, terminally or nonterminally, in the sequence. When phylogenetic change involves the simultaneous addition or deletion of two or more states from a character's ontogeny, hypotheses of character state order based on ontogeny will not reflect phylogenetic order.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0151:AUTUOO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Otolith growth increments were used to estimate the age of 113 larval red drumSciaenops ocellatuscollected in the north-central Gulf of Mexico in October 1983, October 1984, and September 1985. Larval growth, as estimated by correlating age with length and dry weight measurements, was exponential and positively associated with water temperature. Mean growth in length of larvae smaller than 4 mm was relatively slow (≈0.3 mm/d), but at sizes larger than 4 mm, length increased rapidly. Based on growth equations, the mean increases in length of 4–6-mm larvae in October 1984, October 1983, and September 1985, were 0.4, 0.5, and 0.6 mm/d, respectively. These increases in larval growth were associated with increasing water temperature at time of capture; ranges in temperature during the three periods were 24.5–25A, 25.5–26.5, and 27.8–29.0°C, respectively. Larvae that developed in October 1984 grew to a length of 6 mm in about 15.0 d, whereas in September 1985, at the warmest temperatures, larvae grew to 6 mm in only 11.7 d. Unlike those for age–length and age–weight, length–weight relationships were negatively associated with water temperature and growth rates. Therefore, larval age must be considered if length-weight relationships are used as a measure of body condition.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0159:AAGORD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The formation of growth increments in the otoliths of wild-captured larvae of milkfishChanos chanoswas validated by the oxytetracycline-labeling method. Immersion of the fish in 400–500 mg oxytetracycline/L for 24 h is recommended for marking the otoliths of milkfish larvae. A golden-yellow band and the newly deposited growth increments in the otolith were both discernible after marking. Otolith growth increments were deposited at the rate of about one per day, and their formation rate was unaffected by the growth rate of the fish. However, increment width varied with the growth rate of fish. Therefore, otolith growth increments are a valid characteristic for determining daily age and for studying the growth history of wild milkfish larvae.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0168:VODGII>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A bioassay procedure to assess habitat quality was tested on Port Austin reef in southern Lake Huron, a spawning area of lake troutSalvelinus namaycush. In 1986, Plexiglas incubators filled with fertilized lake trout eggs were buried by scuba divers in rock rubble at two sites. The incubators then were attached to chains between large trap-net anchors on the bottom and left over winter. At one site, egg hatch rate was significantly higher in incubators that remained buried in substrate (24%) than in incubators that were dislodged out onto the substrate (13%). At the other, more exposed site, no significant difference was found in percent hatch between eggs that incubated in (10%) and on (8%) the substrate. Percent hatch at both sites was significantly lower than that (40%) of eggs from the same source that were incubated in controlled laboratory conditions. In autumn, concentrations of dissolved ammonia, hydrogen sulfide, and nitrate near bottom and in the substrate posed no threat to lake trout embryos and were not correlated with hatch rate; concentrations differed significantly between the two sites. During winter, 15 cm of sediment settled from the water onto the reef but did not accumulate or smother the eggs. The bioassay procedure is easy to implement, is recommended for use in the Great Lakes, and could be adapted easily for use elsewhere.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0175:FTOABP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Fish detect chemical stimuli through two major chemosensory channels, olfaction and gustation. All current evidence indicates that olfaction is a major mediator of chemical signals and is involved in diverse teleost behavior. This paper describes the morphological components and the basic principles of developmental patterns of the olfactory organ as well as cellular differentiation of receptors in rainbow troutOncorhynchus mykiss(formerlySalmo gairdneri). The olfactory organ originates from an anlage formed by the ectoderm on the ventrolateral part of the head during stage 19 (11 d postfertilization). Ciliated receptor cells appear at stage 24 (day 18) and dominate until immature microvillar receptor cells develop in stage-28 (day 26) embryos. During this period, the olfactory placode continues a lateral and upward migration. At stage 29, the day of hatching, the olfactory groove is enclosed by flaps of skin, and by stage 33, distinct anterior and posterior nares are formed. Spontaneous electrical activity is recorded from the olfactory mucosa as early as stage 25, and neural responses to chemical stimuli are induced from stage-26 embryos that contain sparse ciliated receptor cells. Stereochemical specificity of receptor responses is evident at these stages. We conclude that the olfactory receptor has two ontogenetically distinct forms, ciliated and microvillar. By the time of hatching, both cell types are mature and capable of responding and discriminating among chemical stimuli. The functional distinction of the olfactory system is discussed further in relation to the gustatory system, which is endodermal in origin and is still incomplete at hatching.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0183:SAFDOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The persistence of the embryonic (optic) fissure into adulthood and development of the falciform process in the eye varied among three fish species: guppyPoecilia reticulata, Mozambique tilapiaTilapia mossambica, and brown trout Salmo trutta. The falciform process is a ridge of pigmented and vascular tissue associated with the embryonic fissure in teleosts. In guppies, the embryonic fissure closed during embryonic development, and no falciform process developed. In Mozambique tilapias, the embryonic fissure persisted into adulthood but was lined only with retinal pigment epithelium and lacked photoreceptive layers; it was associated with a partially formed falciform process. In brown trout, the embryonic fissure remained well defined with both retinal pigment epithelium and photoreceptor layers, and the falciform process was well developed. The temporal zone of the fissure in adult brown trout exhibited active growth and had a ventral area of high cone density. The well-developed fissure in brown trout and the oblique orientation of its ventrotemporal cones relative to incident light may be correlated with the species' ability to locate prey above and in front of its body. This system also may allow brown trout to detect polarized light, which could assist in navigation during migration.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0195:EFITEA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor