摘要:

Equipment has been developed and used to follow the movements of free‐swimming individual fish in the sea. A pulsed ultrasonic transmitter inserted into the stomach is tracked by measuring differences in the time of arrival of the acoustic pulses at an array of omnidirectional hydrophones. The method was used to plot the movements of cod in an enclosed sea‐loch. After an initial phase of active movement the cod became less mobile and adopted a nocturnal cycle of activ

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04541.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Scales of 497 dace from the river Stour and 573 from the river Frome were used for age determinations. Annuli were laid down in late May to early June at the start of the growth period. Minimal growth occurred from November to April. Male dace grew minimally faster than females; Frome dace faster than those from the Stour. Growth rates in the two rivers were similar to those published for most other European waters. Variation in growth rates in different years was not great, but there were marked differences in recruitment success. Spawning occurred in the second half of March and elaboration of the gonads between September and March. Immature dace have an annual cycle in condition with a maximum in June and a minimum during the winter months. The condition of the mature females is affected by the gonad cycle. The fecundity of Stour dace is represented by the formula:and for Frome dace by:Most dace were mature by age IV, but there were more mature II and III group fish in the Frome population. Molluscs and Trichoptera larvae comprised the bulk of the winter diet of Stour dace, and Ephemeroptera nymphs,Simuliumand chironomid larvae were the principal constituents during the summer.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04542.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The results of the application of Schnabel (Chapman modification), Schumacher&Eschmeyer, Fisher&Ford, and Jolly capture‐recapture techniques on theBarbus barbus(L.) population in four areas of the middle Severn are compared. The survival of tagged fish varied in different areas and fish released in some time periods were less vulnerable to recapture than fish released from other samples. It is suggested that the shoaling behaviour ofBarbus barbusresulted in non‐random mixing of marked fish. The average population size ofBarbus barbusgreater than 18 cm in length in each of the four sections for the total period of investigation gave population densities ranging from 0.024/m2to 0.202

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04543.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Five hundred and thirty one of a total of 3122 taggedBarbus barbus(L.) in the middle Severn were recaptured using electric fishing and angling. Ninety two barbel were recaught downstream of the site of tagging, 152 upstream and 287 did not move. Electric fishing was selective for home recaptures. The barbel population was divisible into mobile and static components; 86% remained within 5 km, the remainder wandering more widely up to a maximum of 34 km from their site of tagging. Movement seemed to be dependent on size of the fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04544.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Synthetic detergents are reported to be acutely toxic to fish in concentrations between 0.4 and 40 mg/1. Factors affecting toxicity include the molecular structure of the detergent, water hardness, temperature and dissolved oxygen concentration; the age and species of the test fish, and acclimation to low concentrations of detergent. Some of these factors appear to be of only limited importance. Gill damage is the most obvious acute toxic effect; the immediate cause of death may be asphyxiation, but detergents may also be toxic internally. Lethal effects not related to gill damage have not been investigated. Sublethal effects include retardation of growth, alteration of feeding behaviour and inhibition of chemoreceptor organs. Low levels of detergents may also increase the uptake of other pollutants. Invertebrates, especially in their juvenile stages, are extremely sensitive to detergents: concentrations below 0.1 mg/1 interfere with growth and development in some species. The interactions between detergents and proteins, and their influence on membrane permeability may be the basis of the biological action of detergents. Detergents in natural waters are usually partially degraded, and a maximum permissible concentration of 0.5 mg/1 would probably be harmless under most conditions.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04545.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Argentine pejerreys were collected in Lake Peñuelas during January 1973. Calculated growth rate was maximum during the 3rd year of life. The length–weight relationship was: logW=‐5.69395+3.25248 logLwhereW=weight (g), andL=total length (mm). Agegroup I was sexually mature. The sex ratio was 85 males (54%) to 73 females (46%). Young‐of‐the‐year pejerreys fed primarily on copepods, but cladocerans [Bosminasp. (Baird),Diaphanosoma brachyurum(Liéven),Simocephalus serrulatus(Koch)], ostracods, and dipterans were also represented. Feeding occurred duri

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04546.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Scanning microscopic observations were made of the surface structures of isolated scales ofTilapia mossambica(Peters). The circuli were found to form numerous minute processes called scalar denticles, which may act to secure the position of the scale with reference to surrounding dermal tissues. The skin covering the lunula of the scale includes a number of pores which are thought to represent the terminal openings of dermal mucous cells. This part of the skin also shows peculiar epidermal surface patterns. These surface patterns may be indicative of areas subject to increased mechanical stress.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04547.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The electrophoretic patterns of the general proteins, esterases, creatine kinase and phosphoglucomutase of white muscle from Lough Neagh pollan, Lough Erne pollan, Lake Bala gwyniad, Loch Lomond powan, Haweswater schelly and Bassenthwaite vendace are consistently of three types. It is therefore suggested that the coregonids examined are three distinct species: the pollans; gwyniad, powan and schelly; vendace. Vendace is genetically closer to the gwyniad group than to the pollans.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04548.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

CarpCyprinus carpioL. populations of known composition as to size and descent were fished in drainable ponds in various ways to judge the validity of the mark‐recapture method for estimation of population size. Six combinations of gear for capture and recapture were employed, including fyke‐traps, seines and angling‐rods. Satisfactory estimates could be obtained only when the selectivity of the gear for recapture differed from that used for marking. Some differences and changes in behaviour of the carp underlying observed biased estimates are exa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04549.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The annual reproductive cycle of the catfish,H. fossilis(Bloch) is divided into the preparatory period (February‐April), the prespawning period (May‐June), the spawning period (July‐August) and the postspawning period (September‐January). During the early postspawning period (September‐November), the hypothalamo‐hypophyseal‐ovarian system shows a gradual regression. In January, the hypothalamic nuclei, the pars magnocellularis (PMC), the pars parvocellularis (PPC) of the nucleus preopticus (NPO), and the nucleus lateralis tuberis (NLT) show renewed activity, as shown by a significant increase in their nuclear diameters and an accumulation of neurosecretory material (NSM) in their cell bodies. The hypophysis and the ovary remain quiescent. During the preparatory period, all the hypothalamic neurons studied indicate decreased activity but simultaneously show an accumulation of NSM in their cell bodies. The number of granulated basophils in the proximal pars distalis (PPD) of the hypophysis remains low but ovarian weights increase, presumably due to the multiplication of oogonia. In the prespawning period, there is a marked accumulation of NSM in the cell bodies of the hypothalamic neurons and at the same time the number of granulated basophils in the PPD of the hypophysis dramatically increases with concomitant increase in vitellogenic activity in the ovary. During the spawning period, the hypothalamic neurons continue to store NSM in their cell bodies and simultaneously there is a tremendous increase in the number of granulated basophils in the PPD of the hypophysis and the ovary has a large proportion of yolky primary oocytes. Spawning is associated with a significant degranulation of the granulated basophils in the PPD of the hypophysis. The significance of the results is discussed in relation to the environmental and hormonal regulation of seasonal ova

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb04550.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY