摘要:

Hatchery-spawned bluegillsLepomis macrochiruswere reared in controlled laboratory conditions to evaluate the effects of water temperature, photoperiod, and feeding rates on opaque and translucent band formation in otoliths. Opaque bands were associated with periods of slow growth, and translucent bands were associated with periods of fast growth. Marginal increments (translucent bands distal to opaque bands) formed at 22°C or higher water temperatures. Although opaque bands formed, no marginal increments formed when water temperature was below 22°C. Fish exposed to a cycle of warm water (≥22°C), cool water (<17°C), and warm water formed a second opaque band and marginal increment. Opaque bands and marginal increments formed in bluegill otoliths at similar temperatures in outdoor tanks, in two lakes, and in the laboratory. Opaque bands also were induced by changes in photoperiod and feeding rate; however, the effects of photoperiod and feeding rate were inconsistent, and the opaque bands formed were typically faint compared to those resulting from temperature changes. Bluegills spawned in May 1984 and held in outdoor tanks during September 1984–December 1985 formed an opaque band in their otoliths during February–June. The opaque band is considered a valid annulus for age-1 bluegills.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0546:FOAIOO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

During an 18-month study, we monitored (by beam trawl and tagging) a year-class of Dungeness crabsCancer magisteras crabs grew and as males recruited to the fishery at 154 mm in notch-to-notch carapace width (CW). We used an enhanced size-frequency analysis to estimate that males, inferred to be 2 years old in summer 1985 and mainly in the 104-mm (mean CW) instar, molted twice during an 18-month period to attain the 156-mm instar (SD = 13 mm). About 58% of males in the 156-mm instar had attained legally harvestable size. Similarly, females inferred to be 2 years old in summer 1985, and mainly in the 103-mm instar, molted to the 121-mm instar during summer and autumn 1985 and subsequently appeared to molt annually. Our size-frequency analyses were enhanced by (1) incorporating regression statistics for growth increments versus CWs, (2) simultaneously analyzing several size-frequency distributions obtained sequentially in time, and (3) accounting for the exploitation of legal-sized males. Our results for females indicated decreasing SDs of CWs for successive instars. This pattern follows from the negative relationship between the size of molt increment and CW, and it might be anticipated for other crab species with a similar growth function.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0556:GOMAFD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In this paper, I present a model to estimate total participation in marine recreational fishing in the USA. I used the model to forecast the number of marine recreational fishermen in the years 1985, 1990, 2000, and 2025. The multivariate regression model explained almost 90% of the variation in numbers of anglers by the variables of state population size, population size of coastal counties, angler age, and length of tidal coastline. From this model, participation was forecast to increase in each state, particularly in those in the southeast USA. Overall, the number of marine anglers was forecast to increase 30% between the years 1980 and 2025 to nearly 14 million in marine coastal states. In addition, I illustrated how the forecasts of total participation can be used to roughly project the participation and fishing effort in specific fisheries.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0564:FOIPIM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Otolith shape differed among Florida largemouth bassMicropterus salrnoides floridanus, northern largemouth bassM. s. salrnoides, and the first-generation (F1) hybrid between these two subspecies. As fish grew, Florida largemouth bass otoliths became progressively longer along the anterior axis and less wide along the dorsal axis than those of the northern subspecies; otolith measurements of F1hybrids were intermediate between those of the two subspecies. Computations of back-calculated lengths that disregard these variations in the relationships of body length to anterior otolith radius and body length to dorsal otolith radius could cause bias in comparative age and growth studies, especially in newly established multistock populations. Because the differences in otolith morphometry were more evident along the dorsal plane, greater sources of error may be encountered when otoliths must be sectioned and measured than when whole-view measurements are used.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0573:NDIOMA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-118.5.576

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor