摘要:

AbstractWe tested the hypothesis that small fishes avoid piscivores by increasing their use of shallow water areas, thereby reducing the capture success of the piscivore. Experiments were conducted in 600‐1 aquaria, using perch (Perca fluviatilis) as the piscivore and minnow (Phoxinus phoxinus) as the prey. Two size classes of minnows, presented alone and together, were placed together with perch in aquaria with and without shallow water areas. The capture success of perch and use of depth by minnows changed as predicted by our hypothesis. In addition, we observed a decrease in the shoal size of minnows when perch were present. Perch selected large minnows over small minnows when both size classes were present, probably because large minnows were a more energetically profitable prey siz

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00101.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe investigated the implications of early maturation in a central Ontario population of pumpkinseed (Lepomis gibbosus) by comparing the growth trajectory, body condition, lipid to body weight ratio and past growth history of mature and immature females through the 1992 growing season. Pumpkinseeds were sampled from Beloporine Lake from May 28 to July 24 and on November 20, just prior to freeze‐up of the lake. Prior growth history and length at age were determined by backcalculation from scale annuli. Nearly all females age 3 and older had matured in 1992, so we focused on age 2 females (22% mature). Females that matured at age 2 were significantly larger at the end of their first year of life than those that did not mature at age 2, although there was no significant difference between groups in the prior year's growth rate. The mature age 2 females were significantly larger than immatures, at the beginning and end of their third growing season, but not during the June 2 ‐ July 19 breeding season. The condition factor of mature females was higher than that of immature females on all but one collection date. However, the mean somatic lipid‐to‐body weight ratio was higher in immature females on all sample dates and significantly higher over the grwing season. We conclude that the costs of early maturation include lack of length and weight gain during the breeding season, and loss of stored lipid. The latter may be associated with increased overwinter mo

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00102.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractSince 1972, numerous impoundments throughout Texas have been stocked with Florida largemouth bassMicropterus salmoides floridanus.In order to examine some of the long‐term effects of such efforts, the present study summarizes past studies and complements those with more current observations on the intergrade largemouth bass population in Aquilla Lake, Hill Country, Texas. The reservoir received 4 annual stockings during the month of May from 1982 to 1985. Collections occurred periodically from February 1984 to June 1987, February to August 1988, and monthly from August 1991 to November 1992. Horizontal starch‐gel electrophoresis was conducted to determine allele frequencies at locisAAT‐B*,SOD*1. Mean heterozygosity and percent introgression were highest for age‐0 fish of the 1986 year class. Assortative mating was not apparent in 1991 or 1992 year classes. Collections of specific year classes over time consistently indicated decreases in the relative abundance of the northern phenotype. Relative to the northern phenotype, the abundance of Florida year classes remained relatively constant over time. Relative abundances of F1hybrids and Fx, intergrades (i. e., F1) from specific year glasses were observed to generally increase w

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00103.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractThe population dynamics of Atlantic salmon (Salmo salarL.) and brown trout (Salmo truttaL.) were compared in a small tributary of the River Scorff (Brittany, France) from spawning time to the beginning of the third growing season. The spawning and fry emergence of the two species took place at approximately the same time. In the first autumn, the densityof 0+ juveniles and settling rate from the egg stage were much higher in trout than in salmon. The emigration rate from 0+ population was much higher in trout than in salmon. The size of resident and migrating fish was always smaller in salmon than in trout, whatever the age. The low level of salmon production in the brook, compared with trout, was the result of low survival from egg to 0+ stage in autumn, combined with the small proportion of juveniles migrating after the first growing season. This was not compensated by a high number of migrants the next year. The role of physical habitat, inter‐and intraspecific competition, predation and migration dependence on size and early sexual maturity is discussed. Indications are that small tributaries of the type studied are of great value for recruitment in trout but not very productive for juvenile salmo

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00104.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

AbstractWe studied the movements of redbreast sunfish (Lepomis auritus), bluegill (Lepomis macrochirus), rock bass (Ambloplites rupestris), largemouth brass (Micropterus salmoides), and warmouth (Lepomis gulosus) by tagging fishes with individually numbered tags. We sampled quarterly over a 3‐year period (1985–1988) at six 800‐ to 2300‐m‐long sites in 2 streams near Oak Ridge, Tennessee. Overall, distances between successive captures were10 km. In general, all species were highly sedentary in both streams, with rock bass and redbreast sunfish being the most sedentary and bluegill and largemouth bass being the least. In most instances, redbreast sunfish showed the same distribution of distances between captures regardless of the interval between captures (1 week, 3 months, 6 months or more). This species also tended to be more mobile in the spring and less mobile in the winter, with large fish exibiting the greatest distances between captures. Some redbreast sunfish showed a very restricted home range, being captured 3 or more times over ≥ 6 months in the same 50‐m section of stream. A few individuals moved 4‐9 km only to return to their original location, but most fish exhibited behaviors intermediate between these extremes. For all species, upstream and downstream movements were equally common, although movements in one direction predominated at some sites for limited periods of time. Knowledge of movement patterns and differences in behavior among species is important not only in understanding the basic ecology of the species but also in designing, conducting and interpreting environmental

ISSN:0906-6691    

DOI:10.1111/j.1600-0633.1994.tb00105.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY