Editorial Note on Weight–Length Relations of Fishes

Abstract

The weight (W) of fishes (and other organisms) is exponentially related to their length (L) according to the equation W = aL b , where a is the intercept and b is the slope of the log-transformed relation (Le Cren 1951, Froese 2006. Based on the slope (b) of the relation between weight and length, one can check whether the growth of a fish species is isometric (b = 3, all fish dimensions increase at the same rate), hypoallometric (b < 3, a fish increases less in weight than predicted by its increase in length, i.e., it becomes more elongated as it grows; also termed negative allometric) or hyperallometric (b > 3, a fish increases more in weight than predicted by its increase in length, i.e., it becomes less elongated or more roundish as it grows; also termed positive allometric). Weight-length relations (WLRs) can be used for converting lengths into biomass, determining fish condition, comparing fish growth among areas, and as a complement to species-specific reproduction and feeding studies (Petrakis and Stergiou 1995, Koutrakis and Tsikliras 2003, Froese 2006. Thus, they are an important component of fisheries biology and when properly calculated they can be very useful to fisheries management.Over the last decade, the number of published articles dealing with WLRs of fishes is increasing in fast rate (Fig. 1). The majority of articles have been published in specialized fish journals, with 367 out of the 697 articles appear- In this editorial note, we set some criteria and recommendations on important issues (i.e., number of species, sample size, length range and preservation, reporting and Abstract. Weight-length relations of fishes are useful for estimation of biomass from length observations, e.g., in fisheries or conservation research. Here we provide some guidance to authors of such papers, in order to facilitate the publication and review process. EDITORIAL NOTE ON WEIGHT-LENGTH RELATIONS OF FISHES

Length–weight relation for eleven demersal fish species in the artisanal shrimp fishery areas from the Bahia Magdalena-Almejas lagoon system, Mexico

“…We consider results presented in this report an adequate estimation of L-W relation for the eleven species, because the parameter b fell within the expected range of 2.6-3.4 (Froese et al 2011), and the threshold of a minimum number of sampled fishes (100 specimens for each species) was also reached (Froese 2006, Froese et al 2011.…”

“…Prior to regression analysis, log-log plots of the length-weight pairs were performed to identify outliers (Froese et al 2011). Extreme outliers were excluded from the analysis.…”

Length-weight relationships for 30 fish species caught in coastal waters of Veracruz, western Gulf of Mexico

“…According to Froese et al (2011) an adequate sample size of about 100 specimens per species, i.e., there is no need to kill thousands of specimens only for WLR estimates with exception of rare and endangered species as well as specimens that were caught from opportunity sampling.…”

Length-weight relationships and condition factor of the eaglebeak pacu Ossubtus xinguense Jégu, 1992 (Characiformes, Serrasalmidae), an endangered species from Rio Xingu rapids, northern Brazil

“…In relation to growth stanzas between size class, O. xinguense presents a growth type which apparently follows the morphological pattern adopted by Jégu (1992), juveniles (up to 10 cm SL) have positive allometric growth (b = 3.117), while the adults have negative allometric growth (b = 2.716). Nevertheless, the LWR provided to juveniles, although significant (t-test, P < 0.05) and with high correlation (R 2 = 0.99), should be observed with caution due to the low sample size (N = 19), far from the minimum of 100 specimens recommended by Froese et al (2011). Taking into account the condition factor (K), the females of O. xinguense display K value higher than males.…”