排序方式: 共有5条查询结果,搜索用时 15 毫秒
1
1.
Matthew K. Litvak 《Environmental Biology of Fishes》1993,36(2):183-192
Synopsis Many species of shoaling fish are preyed upon by aerial predators. However, to date there has been no analysis of the evasive
response of a group of shoaling fish to an aerial threat or attack. The response of a shoal of fish encompasses a suite of
behaviors starting with a startle response. Shoals of golden shiner, Notemigonus crysoleucas, responded to the threat of aerial predation from a kingfisher model with a startle response, an increase in shoal depth,
an increase in polarity, swimming in the opposite direction under the model predator, shoal compression along the depth axis,
and shoal expansion on the plane perpendicular to the depth axis. It was hypothesized that shoal compression along the depth
axis serves to increase predator confusion by placing more fish in the predator's visual field. This compression was termed
the ‘plane of confusion’. 相似文献
2.
Avoidance thresholds and 96-h LC50 values were determined for golden shiners, Noiemigonus crysoleucas , for five individual elements: chromium, Cr; copper, Cu; cadmium, Cd; arsenic, As; selenium, Se. The avoidance concentrations were 73, 26 and 28 μgl-1 for Cr-VI, Cu and As-III, respectively. Cadmium and Se were not avoided at experimental concentrations up to 68 and 3489 μg1-1 , respectively. Acute flow-through 96-h LC50 values were Cr-VI 55·0, Cu 84·6, and As-III 12·5 mg 1-1 , which were more than two orders of magnitude above avoidance concentrations. The acute flow-through 96-h LC50 values for Cd and Se were 2·8 and 11·2 mg 1-1 , respectively. These concentrations are 31 and 2·2 times the highest concentration employed in the avoidance tests, neither of which were avoided by the test organisms. Thus, simple toxicity tests do not identify the environmental hazard of some elements, and the most toxic elements may not elicit a behavioural response. When used in concert with tests of organism function, more realistic indicators of environmental hazard or safety may be determined. 相似文献
3.
4.
Body length variation within multi-species fish shoals: the effects of shoal size and number of species 总被引:2,自引:0,他引:2
Theory predicts that selection should favour phenotypic homogeneity in fish shoals, and field studies have indeed confirmed
that variation in body length within fish shoals is significantly lower than expected from a random distribution of fish among
shoals. We investigated the extent to which variation in fish body length within shoals is determined by the shoal mean of
body length, the number of species in a shoal, and the overall shoal size. We collected 34 fish shoals, ranging in size from
6 to 776 individuals, from the littoral zone of a Canadian lake. Shoals consisted of up to four different species, with multi-species
shoals being larger and more frequent than single-species ones. The strongest determinant of body length variation within
shoals was the shoal mean of body length, followed by the number of fish species in a shoal; i.e. multi-species shoals were
less size-assorted than single-species ones. A more detailed analysis showed that the higher body length variation observed
in multi-species shoals was due to increased body length variation both within and between component species. Shoal size had
no significant effect on body length variation within shoals. Potential explanations of the positive relationship between
body length variation and the number of species in a shoal are suggested. The implications of the above results for the evolution
of multi-species shoals are discussed.
Received: 6 May 1997 / Accepted: 14 October 1997 相似文献
5.
Theory predicts that fish should assort in shoals on the basis of similar phenotypic traits to minimize predation risk and to maximize foraging efficiency. A single phenotypic character, body size, was considered and the hypothesis tested that free-ranging fish shoals are sizeassorted. Furthermore, a second test investigated whether fish within multi-species shoals are more strongly size-assorted with conspecifics than with heterospecifics. Twelve fish shoals, each comprising two different species (golden shiner Notemigonus crysoleucas , and banded killifish Fundulus diaphanus ) were caught in the littoral zone of a north temperate lake using a beach seine. Shoal membership size ranged from 36 to 776 fish, and mean standard body length of members ranged from 18 to 34 mm. Fish were assorted by body size at two different levels, namely, between shoals and at the level of species within shoals. Body sizes of shiners and killifish within shoals were significantly different in seven out of 12 shoals, with killifish being the larger species in five cases and shiners being the larger one in two cases. Because there is considerable overlap in body size between the two species in the population, the observed species-related size-assortativeness within shoals was not just the by-product of a directional size difference (between species) in the population. These findings provide strong quantitative evidence for size-sorting in free-ranging fish shoals and raise questions concerning the formation of multi-species fish shoals. 相似文献
1