Specimens of Brazilian silverside (Atherinella brasiliensis,We present some considerations with regard to the general methodology for adjusting weight-length relationships.

Summary 1. The objective of this study was to identify longitudinal distribution patterns of large migratory fish species in the Uruguay River basin, southern Brazil, and construct statistical distribution models for Salminus brasiliensis, Prochilodus lineatus, Leporinus obtusidens and Pseudoplatystoma corruscans. 2. The sampling programme resulted in 202 interviews with old residents and fishermen at 167 different sampling sites in the major rivers of the basin. Interviewees were asked whether these fish species were present in the nearby river segment, recently or in the past. The average age of respondents was 56 years, and the great majority had resided for more than 30 years in the area where they were interviewed. 3. Fish distribution patterns were modelled using altitude and basin area as environmental descriptors. Distributional patterns were estimated using logistic equations (LOGIT): , where Al is the altitude and BA is the basin area. 4. Accuracies of the distribution models were between 77 and 85%. These accuracies are similar to those of published distribution models for other fishes based on larger numbers of environmental descriptors. 5. The historical distributional ranges make clear that all operating or planned large hydropower dams in the Uruguay River basin, with one exception, limit or will limit the distribution of migratory fishes.

]; where W is the expected weight for a specifi c length L, a 1 and a 2 are the proportionality coeffi cients for stanzas 1 and 2, b 1 and b 2 are the allometric coeffi cients for stanzas 1 and 2, R sc is the stanza changing rate for the switch function and SCP is the stanza changing point for the switch function. The stanza changing point was estimated as 5.28 cm, corresponding with the length at fi rst maturity for this species L mat (5.29 cm). Our data suggest that a complex growth pattern can be in nature, and perhaps not often identifi ed because trends are obscured by natural variability.KEYWORDS. Allometric growth, length at fi rst maturity, reproduction, sexual maturity, length-weight relationship.RESUMO. Crescimento polifásico em peixes: estudo de caso com Corydoras paleatus (Siluriformes, Callichthyidae). Foi estabelecida uma relação peso-comprimento para Corydoras paleatus (Jenyns, 1842) (Siluriformes, Callichthyidae) (n = 596) a partir de amostras obtidas em novembro-dezembro de 2009 e março-abril de 2010, na lagoa da Pinguela (29°46'57"S; 50°11'16"W), Rio Grande do Sul, Brasil. A espécie apresentou um padrão de crescimento alométrico polifásico, cada estágio descrito por uma equação de potência independente e controladas por uma função de interruptora:; onde W é o peso esperado para um comprimento L, a 1 e a 2 são os coefi cientes de proporcionalidade para as fases 1 e 2, b 1 e b 2 são os coefi cientes alométricos para as fases 1 e 2, R sc é a taxa de mudança de fase e SCP é o ponto de mudança de fase. O ponto de mudança fase foi estimado em 5,28 cm, correspondendo com o comprimento de primeira maturação desta espécie (L mat ) (5,29 cm). Nossos dados sugerem que um padrão de crescimento complexo pode ser frequente na natureza, e que talvez muitas vezes não seja identifi cado porque as tendências são obscurecidas pela variabilidade natural. PALAVRAS-CHAVE.Crescimento alométrico, tamanho de primeira maturação, reprodução, maturação sexual, relação peso-comprimento.The weight-length relationship (WLR) is considered frequently as "second class" science (Froese, 2006), and just regular task for any fi shery biologist. Research about WLR are frequently published only as short-communication for species that this information is not yet known (Froese, 2006). As a result, specifi c work on weight and length do not stand out, restricting knowledge of the WLR to a very small number of species (Kulbicki et al., 2005).Of course, it's easy to understand the need of WLR for commercial fi shery, when we need to convert both measurements as an ordinary task. However, the parameters of the WLR, as the proportionality coeffi cient (a) and the allometric coeffi cient (b) could inform several aspects of the fi sh biology, as the general growth pattern or seasonal changes in the fi sh condition (Froese, 2006). The amount of information that could be inferred using this general approach makes it very useful the understand ecological patterns, even for small and not commercial fi sh species. Froese et al. (2014) made a rece...

Angiostrongylus costaricensis is a parasite that infects rodents, including the wild cotton rat Sigmodon hispidus and pygmy rice rats Oligoryzomys spp., among others. However, urban Rattus norvegicus and Mus musculus have not been identified as important hosts of A. costaricensis. In this study, Swiss mice (SW), Wistar R. norvegicus (RN), wild Oligoryzomys nigripes (ON) and a local strain of M. musculus (RGS) were experimentally infected with A. costaricensis. Survival, elimination of L1 (total sum per group, A0), and the number of adult worms recovered divided by the dose of each L3 inoculum (yield ratio, YR) were examined for each group after a 40-day post-infection period. The survival rates, A0 and YR values were: 27%, 207,589 and 0.42 for the SW group; 81%, 8691 and 0.01 for the RN group; and 63.6%, 26,560 and 0.16 for the RGS group, respectively, in each case. The survival rate for the ON group was 100% and the A0 value was 847,050. A YR was not calculated for the ON group since the ON group was maintained up to 565 days post-infection (pi) to examine long-term mortality. At 500 days pi (16 months), 50% of the ON group had died, while one animal (10%) survived 595 days pi (20 months). Taken together, these data indicate that A. costaricensis has undergone a greater degree of adaptation to the wild rodent, O. nigripes, than to R. norvegicus or a local M. musculus strain. In addition, titre curve (A0) modelling of adaptation status proved to be useful in evaluating A. costaricensis-rodent interactions.

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