摘要:

When access to food is restricted, faster growing fish may be those whose behaviour is relatively unaffected by the presence of nearby conspecifics. Behavioural experiments were carried out to determine the relation between growth and motor activity levels in crowded and uncrowded conditions, and measures of aversion/attraction to groups of conspecifics. Two experimental groups of Or)‐ius laripes (Temminck and Schlegel) were grown for several weeks in two environments manipulated so as to maximize differences in social interactions. In the high interaction environment (HI), food was provided inside a floating cork ring. In the low interaction environment (LI), food was spread over the container's surface. Fish were measured at the end of the growth period and tested for their activity levels in the presence of conspecifics and for their preference for, or tolerance of crowded conditions. The correlation between motor activity and growth was significantly more positive in the HI environment than in the LI environment. The relationship between preference for crowded conditions and growth was negative for both groups of fish, although less so for HI than for LI. We conclude that artificial selection for faster growth may produce more aggressive fish only under very high levels of forced social interaction (competition), if at all. Under conditions of reduced social interaction, the social‐aversive or socially indifferent fish grow fas

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02531.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

One‐year‐old Arctic charr, Sulvelinus alpinus (L.), of the Hornavan strain were tested from February 1985 to January 1986 in an attempt to get an increased understanding of the annual rheotactic behaviour as well as the die1 and seasonal locomotor activity pattern. An annular stream tank equipped with photocells was used to measure the direction of swimming movements as well as the number of passings. From February to late May the locomotor activity was low but increased in July and peaked in September. After November the locomotor activity was again at low winter levels. During the activity peak from July to November the majority ofall movements was directed against the current while no preference for direction was noted during the rest of the year. The high level of swimming movements directed against the current in late summer and autumn may be related to an innate habitat change. From February until June, the charr exhibited a bimodal diurnal activity pattern. In July activity was evenly spread over the whole 24‐ hour period and in August and September activity was again mainly diurnal with a bimodal pattern. In October and November the activity was mainly nocturnal and in December and January activity was concentrated in the short light period. Both annual and die1 activity are discussed in relation to earlier findings in general locomotor activity in Arctic charr and other salm

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02532.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Biological and ecological aspects of Lake Garda carpione,Salmo carpio L., are reported. This study reports lower catches and it is suggested that fewer carpione are now in this lake. Opercula and scales have been used for ageing fish and determining the growth rates. Life expectancy does not exceed five winters. Males became sexually active at 2 years (=winters) of age and females at 3 years of age, however, full spawning capability is achieved only in the following year. Our data confirm that carpione have two spawning seasons: winter (a long period) and summer (a shorter one). Carpione are not exclusively planktivorous but adapt their feeding habits to the environment and change the manner and time of their feeding.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02533.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Manipulation of the opportunity to spawn was used to investigate the relationship between endocrine events, egg viability and spawning behaviour in female rainbow trout. Females were prevented from spawning by isolating them from males and gravel for up to 21 days after ovula‐ tion. Blood samples were taken before pairing with a male, at the onset of nesting activity, and at the completion of spawning. Plasma hormone levels of gonadotropin (GtH) and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,2OP) were measured by specific radioimmunoassays. There were no qualitative or quantitative differences in the spawning behaviour of females paired on the day of ovulation or 7. 14, or 21 days after ovulation. There was a general decrease in the viability of eggs with increasing retention times. In females paired on the day of ovulation, or after 7 or 14 days, GtH levels increased with the onset of nesting behaviour and declined as fish reached the post‐spawning condition. By day 21, GtH levels before pairing were significantly higher than prepairing levels in the other three treatment groups, and did not increase at the onset of nesting, or decrease in post‐spawning fish. Plasma 17,20P remained high in prepairing and nesting samples of all four groups and declined to low levels in fish in post‐spawning condition. In females paired on the day of ovulation there was a significant increase in 17,20P from the prepairing to the nesting stage. These results suggest that 17,20P plays a key role in the synchronization of behavioural and maturational events at t

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02534.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The behavioural and physiological effects of surgical implantation of dummy miniature acoustic transmitters into the peritonealcavities ofjuvenile Atlantic salmon, Salmo salar L., were assessed. lntraperitoneal implantations had no significant effect on growth, feeding or swimming behaviour in either parr or smolts. Recovery from the surgical implantation was both rapid and total; infection was absent; and physiological processes such as smoltification and maturation of testes in precocious parr were unaffected. Expulsion of the transmitter through the body wall, not through the implantation wound, occurred in a number of fish but without adversely affecting the animals. The intraperitoneal implantation technique is discussed in relation to its use during biotelemetry studies.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02535.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Sand gobies areextremely abundant in coastal waters and estuaries.Pomuroschistus lozunoitends to be overlooked due to identification problems. This paper summarizes the characteristics to distinguish P. lozanoi from P. minutus and presents a new distinctive feature that allows identification of juveniles from 15‐20 mm standard length onward. The known geographic distribution of P. lozanoi is extended northward to 53°30′ N and southward to 40°N on the coast of Europe. In northern Europe P. loxmoi seems better adapted to the estuarine habitat than previously th

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02536.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Blennioid fishes show a highly differentiated pectoral fin, which they use to cling to the substrate. The lower part of the pectoralis, comprising about four to six fin rays, forms a hook‐field with specific anatomical features: (1) the rim of the fin web has a saw‐like appearance, because it extends from the tip of a fin ray to the shaft ofthe upper of two neighbouring fin rays, (2) the outer half of the bony fin ray carries a lepidotrichal cord composed of fibrocytes, collagen, elastic fibres and acidic GAGS, (3) the epidermis overlying the lepidotrichal cord is differentiated in terms of cyto‐architecture and forms a conspicuous cuticle. The upper part of the pectoral fin does not show any obvious specializations and is used for swimming and undulation. The vascularization of the fin originates from a stem vessel which gives rise to five branches, each supplying two or three neighbouring fin rays. Each fin ray is accompanied by a single arterial vessel at its upper edge. No vessels are found in the space between the bony fin ray halves. The morphology of the shoulder girdle and pectoral fin shows only little variation among the four species of Blenniini studied. Most remarkable is the fusion of the coracoid with the cleithrum, loss of one element of the suspensorium and the absence of branched fin rays. The possible relevance of the Blennioid pectoral fin as a model for the origin of morphological novelties in connection with functional specializations is disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02537.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Hybrids of the Iberian nase, Chondrostoma polylepis, and the pardilla roach, Rutilus lemmingii, were found in the River Yeltes, Salamanca, Spain. Morphological multivariate (PCA) and univariate (ANOVA) analyses of 10 C. polylepis, 33 R. lemmingii and 15 hybrids have shown that the hybrids are intermediate in shape between the parent species, with a stronger resemblance to the nase. A brief discussion of the potential causes of the hybridization is presented.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02538.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

We studied reproductive traits in nine anadromous brown trout, Salmo trutta L., populations in seven Norwegian rivers. Within populations we found a positive significant correlation between fish length and fecundity in all populations, and between fish length and egg diameter in five populations. There were significant differences in these relationships between populations from different rivers, and between populations from different locations within rivers. When adjusted for variation in fish length, mean fecundity and mean egg diameter showed a negative significant correlation among populations. The ratio of gonadal weight to somatic weight (gonadosomatic index) varied significantly among populations but was not associated with variation in fish length. Comparatively few large eggs were found in brown trout populations co‐existing with several other fish specie

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02539.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A primary toxic action of manganese to brook charr, Sulvelinusjonfinalis, at concentrations near or above the 96 h LC50was the disruption of sodium regulation. Body and plasma sodium concentrations of brook charr declined by 52 and 40%, respectively, during exposure to 10.9 mM manganese (in 250 PM CaCI), and all fish died within 36 h. Sodium balance was less severely affected by 2.7 and 5.5 mM manganese. An increase in the external calcium concentration from 0.05 to 1.0 mM raised the LC50for manganese from 4.9 to 5.8 mM, and a further increase to 2.5 mM calcium almost doubled it to 10.2 mM. An examination of stable manganese uptake by the gills revealed that accumulation was inversely correlated with body sodium concentration (r =−0.77). Radioactive J4Mn entered the bloodstream in low levels and accumulated in the liver. Thus manganese may have systemic effects as well as those attributable to surface binding on the gill. Studies of the mechanism ofdissolved iron toxicity were less conclusive, but it did not appear to involve extensive disruption of sodium balance. There was about a 15% drop in body sodium concentration when the trout were exposed for 48 h to the 96 h LC50level of iron, but plasma sodium was unaffected. Also, an iron concentration at twice the LC50did not escalate the loss of body sodium, and increasing the water calcium concentration did not raise the LC5

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb02540.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY