Individual Weight Data Research Articles

Estimating weight–length relationships without individual weight data: an application to the American lobster (Homarus americanus) fishery of Long Island Sound

The estimation of weight–length relationship of fish species requires having data on individual weight and length. However, individual weight data are often not available because they are too expensive or not feasible to gather and the relationship cannot be explicitly estimated. Yet, in this paper I develop a simple methodology that allows me to estimate a weight–length relationship when only aggregate weight data are available. To show its usefulness, the methodology is applied to the American lobster (Homarus americanus) population of Long Island Sound. Results indicate the existence of isometric growth for American lobsters in this geographical location: W = 0.000924L 2.9619. The estimated relationship is used to predict individual weight of lobsters which are then used to construct biomass indexes for three size classes of lobsters for the time period 1987–2006. This analysis suggests that is not necessary to invest efforts in collecting individual weight data to be able to construct meaningful indicators of fish population.

Growth curves of body weight changes in laboratory-bred female African green monkeys (Cercopithecus aethiops)

Nonlinear growth models having three or four parameter family were applied to individual weight data of female African green monkeys for estimating their growth pattern. The body weight was measured continuously from birth to six years of age with five female laboratory-bred monkeys. A total of 95 weight data were collected from each monkey. The average body weight was 330 g with the standard deviation of +/- 15 g at birth, and 2.71 +/- 0.33 kg at four years of age. The body weight of female African green monkeys was judged to reach a plateau after about four years of age. Five growth models (Gompertz, Logistic, Richards, Bertalanffy, Brody) were applied to these weight to age data. The most suitable coefficient of determination between growth data and growth model was obtained by the application of Gompertz equation. Three parameters of Gompertz equation, mature size (A), rate of maturing (K) and inflexion point (e-1 A) were analyzed in relation to age of menarche. Strong correlations between age of menarche and maturing rate, as well as between age of menarche and inflexion point were observed.

A population dynamics approach to the estimation of production of four calanoid copepods in Lindaspollene, western Norway

Estimates were made of copepod production, based on estimates of recruitment, mortality. development times and individual weight data, and the methodological approach given earlier by Sonntag & Parslow is further developed. In addition to estimates of cohort production, the present approach includes estimation of daily production in depth and time. The estimation method is applied to abundance data of the copepodids of Pseudocalanus elongatus, Paracalanus parvus, Temora longicornis and Centropages hamatus obtained in LindAspollene in 1981. Production during June was estimated as 446, 252, 231 and 63 mg ash-free dry weight m-' respectively. Production of P. parvus and C. hamatus was primarily concentrated in the upper 5 m, while that of T. longicornis and P. elongatus was located below 5 m depth. The cohort P/B ratios were estimated in the range 2.5 to 6.8. The daily P/B ratios (including data for Calanus finmarchicus) were strongly dependent on the stage of development within the populations, but did not seem to differ much between species.

The aquatic Coleoptera of Øvre Heimdalsvatn

The species composition, seasonal and spatial distribution, and biomass of the coleopteran Fauna of the exposed zone of Øvre Heimdalsvatn in 1972 are presented. Individual weight data are given for the 8 species present in the lake: Haliplus fulvus F., Hydroporus palustris L., Deronectes alpinus Payk., D. multilineatus, Flkstr., D. rivalis Gyll., Platambus maculatus L., Colymbetes dolabratus Payk. and Helophorus glacialis Villa. Deronectes alpinus occurred in highest densities, but P. maculatus, on account of its higher individual weight, was the major contributor to the coleopteran biomass.