摘要:

Two closely related and morphologically similar gadoid predators, saithe,Pollachius virensand pollackP. pollachius, coexist in close proximity on a submerged reef in Loch Ewe, Scotland. The degree of overlap between the niches of these two gadoids in the wild was investigated by means of acoustic tracking, underwater television and an examination of stomach contents. Simultaneous tracking of individuals of both species revealed that pollack generally swim more slowly than saithe, restricting much of their movements to the submerged reef. Saithe ranged more widely around the reef as part of a school during the day, moving onto the reef at night. Video recordings showed that saithe swam actively and foraged in small groups and took prey items from the kelp, whereas pollack tended to remain solitary, maintained station at particular locations for minutes at a time and apparently used the kelp forest exclusively for cover. Although the dietary overlap of the two predators was considerable, their intake of different prey groups varied. In particular, within the crustaceans, saithe took amphipods, while pollack took mysids. In addition, saithe consume a wider range of prey than pollack. The relationship between the movement patterns and the use of food resources by these two predators is discussed, with particular emphasis on differences in feeding strategies.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01080.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

During development, form and function (behaviour) change while the match between them must be maintained. The quality of this match determines the importance of morphological parameters in constraining behaviour. If the match is close, the morphology of organisms will be more constraining to the behaviour than when there is a large reserve capacity that creates a certain flexibility. This leads to two questions: (1) How good is the match between form and function during development? The quality of the match necessarily changes during development because changes in structural capacity often cannot proceed at the same speed as changes in functional demand. The evidence for these changes is discussed. (2) What are the mechanisms that maintain the match between form and function during developmental and evolutionary changes? Two mechanisms for maintaining the match are discussed: (a) reserve capacity and (b) flexible muscle activity patterns. Special emphasis is given to fish examples throughout this review.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01081.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The larvae of 15 freshwater fish species from Lake Trichonis (western Greece) are described from field samples and laboratory‐raised fish. Larval morphologies are compared to identify distinguishing characters. The potential utility of these data sets for assessing phylogenetic relationships is discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A stochastic dynamic programming model is developed of prey choice by three‐spined stickleback. The fitness function relates growth ratekfrom the von Bertalanffy growth equation to stomach fullness. It is shown that the model predicts experimental results. Emphasis is given to handling time as an important variable determining diet. Two handling time vectors are defined, each of which is used to represent the benthic and limnetic morphs found in Paxton Lake, Texada Island, BC, Canada. The model is then used to examine the growth rates to be expected from these two morphs in habitats which vary in the distribution of encounter probabilities with each prey size and the distribution of prey size specific risk of predation. The benthic morph grows faster than the limnetic in most habitats but often the two do as well as each other. In the one habitat where limnetics grow better, they do so because their shorter handling times for small prey counteract the effect of a constant but high risk of predation. The results are discussed in the context of what is known of the ecology and evolution of the two morphs in Paxton Lake. It is concluded that the model is only dealing with conditions in the benthic habitat and data are required on encounter rates and prey size distributions in the linnetic habitat so that the model can be used to predict growth for limnetic

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01082.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Stomach contents of 252lago omanensiswere examined. Sharks were collected in deep water between 150 and 450 m depth off the Marine Laboratory of Eilat. This species feeds on benthopelagic fishes, deep water cephalopods, crustaceans, benthic molluscs and polychaetes. Cephalopods were the main food ofI. omanensis, except during the summer when fishes (mainly myctophids) were ingested in greater quantity. Stomachs also contained terrigenous plant matter, animal remains and large quantities of mud. Prey taxa included two new cephalopod records for the Red Sea.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01284.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Piscivorous fishes tend to be able to consume other fishes early in development and generally experience a dramatic increase in growth after the ontogenetic diet shift to piscine prey. Hence, an acceleration of the onset of piscivory may be favoured strongly by natural selection. Temperate freshwater piscivores, for example, becomes piscivorous at a relatively young age by spawning in advance of, and thereby achieving a size advantage over, the young of their piscine prey. Research in various North American estuaries suggests that young‐of‐the‐year (YOY) bluefishPomatomus saltatrix, an offshore‐spawning estuarine‐dependent marine fish, may accelerate the onset of piscivory by being advected to higher latitudes and timing their estuarine entry with the appearance of small coastal fishes. This hypothesis was tested by: (i) determining the annual recruitment date of YOY bluefish and their prey; and (ii) examining the diet and prey size preferences, and predator size‐prey size relationships, of YOY bluefish in two different estuarine systems: Great South Bay, and the lower Hudson River. Results suggest that the relationships between bluefish and their prey are determined by a complex interplay between recruitment timing of both predator and prey, prey size availability, predator selectivities, and the timing of vernal warming. It is concluded that YOY bluefish migration into northern estuaries at an advanced size provides them with a predatory size advantage over their principal piscine prey thereby facilitating an early diet shift to piscivory white minimizing the time spent as p

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01083.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Furunculosis was first discovered in a fish farm in Norway in 1964, following the importation of rainbow trout from Denmark. The disease spread to several farms and to wild fish in the River Numedalslågen, occurring there until 1979. It was eradicated at several farms, the last being disinfected in 1969. In 1985, furunculosis was discovered in marine fish farms in Nord‐Trøndelag, following importation of salmon smolts from Scotland. The disease reached Møre og Romsdal in 1988, by which time 32 fish farms were infected in the two counties. By the end of 1992, 550 farms were infected. The disease spread concurrently in natural watercourses, from 22 in 1989, to 74 by the end of 1992. Rapid spread of the disease was associated with several factors including escapes from fish farms, possibly via transport of fish between farms, and natural movement of wild fish in the sea. The disease was not associated with particular physical characteristics in these watercourses, but large aggregations of fish beneath waterfalls combined with high water temperature may trigger disease outbreaks. The ecological consequences of furunculosis are not known. However, some river populations of adult salmon, sea trout and brown trout have suffered. Furunculosis may result in serious negative consequences for populations if a significant number of the brood stock die before spaw

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01285.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In this review and synthesis, new data from field and laboratory experiments on red drum,Sciaenops ocellatus, larvae as prey to larger fishes are presented to illustrate two approaches to the study of developmental effects on predation. Various sizes and species of predatory fishes imposed very different levels of mortality on experimental populations of red drum larvae. Differences in predator size explained little of the overall variation in mortality rates. In the laboratory, responsiveness of red drum to a single size and species of predatory fish was relatively low through much of the developmental period but increased steadily. Response effectiveness improved and the predator's capture success decreased once the prey exceeded 20 mm in length. General ontogenetic trends in the behavioural interaction of various larvae and their piscine predators are described by combining 22 data sets on a scale of roughly comparable ontogenetic state. This scale, together with absolute and relative measures of predator and prey size, are used to assess the roles of ontogeny and scaling in the predation interaction. Ontogeny is shown to be a significant contributor to changes in responsiveness, response effectiveness, and capture success. The influence of scaling always took the form of an interaction with ontogeny and not a main effect.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01084.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Samples collected monthly from the Swan Estuary between March 1978 and May 1979, together with environmental data for 1977 to 1980, have been used to elucidate various aspects of the reproductive biology ofAmniataba caudavittatain this estuary. The gonads ofA. caudavittalastarted to develop rapidly in the spring, when day length, water temperatures and salinities were increasing markedly. Spawning, which occurred mainly towards the top end of the upper estuary, was initiated in November, when water temperatures and salinities in that region werec. 24° C and 9‰, and it peaked in December/January when they werec. ITC and 17%○, Maturity is attained by at least the majority offish at the end of the second and each subsequent year of life. Although some of the larger 1‐year‐old fish attained maturity, this occurred in only one of the two tributary rivers, possibly reflecting differences in the salinity regimes in these rivers. Fecundities ranged from 50 000 in a 150‐mm fish to 705 000 in a 254‐mm fish, with a mean of 310 000. The mature, unfertilized eggs are small and spherical and have a diameter of 560 μm. The larvae are pelagic and characterized by an elongate body, which becomes moderately deep and laterally compressed during development, a short to moderate, tightly‐coiled gut, a distinct gap between the anus and the origin of the anal fin and 25 or 26 myomeres. The development of fins and settlement ofA. caudavittatalarvae occurs at a smaller size than in the larvae of other terapontid species previously described. The success ofA. caudavittatain the Swan Estuary can be attributed in part to its production of very large numbers of eggs at a time when, due to low fresh water discharge and a smait tidal range, conditions in the estuary are relatively stable. Comparisons between the biology ofA. caudavittataand that of other abundant teleosts that spawn in south‐western Australian estuaries show that these species exhibit a wide range of reprod

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01286.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The intracellular pathway of a endocytosed glycoprotein has been studied in rainbow trout (Oncorhynchus mykiss) liver by means of differential and isopycnic gradient centrifugation. When125I‐tyramine‐cellobiose‐labelled asialoorosomucoid was injected intravenously, the protein was removed rapidly from the blood by hepatic endocytosis. The tracer was localized initially in a small, slowly sedimenting organelle (endosome) and transferred to the denser lysosomes where degradation took place. This process took several hours at the acclimated temperature of 10 ° C. The transport could be accelerated markedly or retarded by transfer of fish to higher or lower temperatures respectively. The intracellular transport steps were more susceptible to changing temperature than the internalization process. In particular, the degradation was temperature sensitive. These results may have implications for the effects of changing temperature on immune function in fishes. The impairment of transport upon a rapid temperature decrease, will reduce the rate of antigen processing and presentation in these a

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01287.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY