Biology and population dynamics of the long-finned squid Loligo plei (Cephalopoda: Loliginidae) in southern Brazilian waters

Population structure and reproductive patterns of the long-finned squid Loligo plei off the coast of Santa Catarina, southern Brazil, were analysed from the biological samples of commercial catches landed in the Itajaı́ harbour from April 1995 to February 1998. The species were recruited to the trawl fishery at 130 mm mantle length (ML) and males were, on average, nearly 1.3 times larger than females. The exponents of males and females ML–weight relationships were 1.89 and 2.07, respectively, and differed significantly between maturity stages. Cohorts of both sexes did not persist into their second year, a feature that, coupled with the scarcity of spent animals, provided evidence for semelparity with nearly 1 year life span. An extended seasonal breeding and spawning pattern was characterised with a large reproduction event concentrated during the summer months extending through autumn and winter. It is suggested that the summer spawners hatch during the summer–early autumn, recruit to the fishery in the spring and reach maturity in the following summer, at the age of nearly 1 year. Squid spawned during the winter will hatch during winter–early spring, recruit to the fishery during the summer and autumn and spawn in their second winter. Between summer and winter spawning events, continuous spawning activity produce several microcohorts detected in trawlers catch. Summer spawners sustain the most important commercial concentrations. The relationship between L. plei population structure, seasonal abundance and the dynamics of environmental conditions off southern Brazil is discussed

Gladius and statolith as tools for age and growth studies of the squid Loligo plei (Teuthida: Loliginidae) off southern Brazil

Statolith and gladius were investigated for their suitability as tools for age and growth studies in the loliginid squid Loligo plei off southern Brazil. Statoliths when polished, revealed a series of concentric increments deposited around a nucleus. Consistent increment counts covered the squid's entire life-time and could be considered suitable for individual age estimation. Growth increments were observed on the dorsal surface as delimited by consecutive marks formed during low growth periods. Because early growth was masked during chitin deposition, total increment counts underestimated individual age. Gladius growth was highly correlated with somatic growth, and gladius increments could be used to reconstruct individual growth histories. Both statolith and gladius increments were deposited with the same, possibly daily, periodicity. It could be inferred that L. plei off southern Brazil might live up to around nine months of age

Validação de incrementos de crescimento diário dos estatólitos das lulas brasileiras\ud Doryteuthis plei e D. sanpaulensis (Cephalopoda: Loliginidae)

Este artigo descreve o primeiro estudo bem sucedido sobre validação dos\ud incrementos de crescimento dos estatólitos das lulas Doryteuthis plei e D.\ud sanpaulensis, capturadas na costa sudeste brasileira. Vinte e nove lulas fora

Validation of daily growth increments of statoliths of Brazilian squid Doryteuthis plei and D. sanpaulensis (Cephalopoda: Loliginidae)

This paper describes the first successful validation study of daily growth increments in the statoliths of the squids Doryteuthis sanpaulensis and D. plei, captured off the Southeastern coast of Brazil. Twenty-nine squid were kept in a laboratory and fed with fish injected with chlortetracycline. The chlortetracycline fluorescent markers were observed in polished statoliths previously exposed to UV light. The number of growth increments between the chlortetracycline marker and the edge of the statoliths corresponds to the number of days elapsed. The capture, transportation and laboratory procedures are described below.Este artigo descreve o primeiro estudo bem sucedido sobre validação dos incrementos de crescimento dos estatólitos das lulas Doryteuthis plei e D. sanpaulensis, capturadas na costa sudeste brasileira. Vinte e nove lulas foram mantidas em laboratório e alimentadas com peixes contendo clorotetraciclina. As marcas fluorescentes de clorotetraciclina foram observadas sob luz UV. Os incrementos entre a marca de clorotetraciclina e a borda do estatólito foram contados e corresponderam ao número de dias decorridos. A captura, o transporte e os procedimentos laboratoriais estão descritos