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Age, growth and natural mortality rates of some cichlid fishes of Lake Malawi (1977)

Tweddle, D. ; Turner, J. L.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 10 (1977), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The growth rates, lengths at maturity, fecundity and natural mortality of several cichlids of importance in trawl catches in Lake Malawi are described. Growth rates were determined by analysis of length frequency data from trawl catches. The breeding season for each species was determined by monthly examination of the gonads, and fecundity determined by egg counts from ripe ovaries. Lengths at maturity were calculated from the proportion of mature fish during breeding seasons. Natural mortality rates were determined from length frequency data from an unfished area of the lake. Values of the growth constant K ranged from 0.487 to 0.671. The ratio of length at maturity to asymptotic length varied from 0.56 to 0.82. Growth parameters are compared with those of other cichlids. Most species mature in their third year. Fecundity was proportional to the square of the length in four of the five species. The species studied appeared to produce only one batch of eggs per breeding season. Instantaneous natural mortality rates ranged from 0.92 to 1.69.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.1977.tb04070.x

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Some effects of demersal trawling in Lake Malawi (Lake Nyasa) from 1968 to 1974 (1977)

Turner, J. L.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 10 (1977), S. 0

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ISSN: 1095-8649

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Exploratory trawl data were used to define demersal fish stocks of Lake Malawi in terms of abundance by depth and area. The mean weight of the catch generally declined with increasing depth. A comparison of initial standing stock estimates and the yield from a commercial fishery over a 7 year period suggests a potential yield of less than half of the initial stock. Over 160 species of fish have been identified in the trawl catch of which over 80% by weight were cichlids. Some of the commonest species of cichlids are listed. The composition of the catch in the heavily exploited southern end of the lake has changed from one dominated by large species of Haplochromis sp. and Lethrinops sp. to one dominated by smaller species.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1095-8649.1977.tb05131.x

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3

Electronic Resource

A hybrid system for dynamic photoelasticity (1975)

Henley, D. R. ; Turner, J. L. ; Taylor, C. E.

Springer

Experimental mechanics 15 (1975), S. 289-294

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ISSN: 1741-2765

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract An ultra-high-speed camera utilizing an acousto-optic device for deflecting light rays is described. The system employs a pulsed-ruby-laser light source used in conjunction with a Cranz-Schardin-type camera thus utilizing the best features of both systems for recording a sequence of photographs. The system has been demonstrated at framing rates of up to 200,000 frames/s and has the potential for considerably faster operation. It features the capability of producing a sequence of dynamic photographs in which the time between succesive exposures can be independently varied. Thus, the frequency at which photographs are obtained can be increased during the times of greatest interest. Experimental results demonstrating these features are given.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02318659

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