Laboratório de Ciências da Pesca (LabPESCA)

Martins, R.S., Camargo, R., Gasalla, M.A. 2018. Is the recruitment of the tropical arrow squid Doryteuthis plei linked to retention processes? A case study case off southeastern Brazil

Squid recruitment depends on the survivorship of paralarvae, as the parental stock dies following reproduction. Recruitment strength is modulated by the physical and biological environmental conditions experienced by paralarvae. To benefit from the favourable environments (i.e. nursery grounds) in the dynamic and fluid pelagic domain, squid paralarvae rely on passive retention in favourable areas by currents to some extent. To evaluate the retention conditions off South Brazil Bight (SBB, 22–29°S) for tropical arrow squid (Doryteuthis plei) paralarvae, we ran a series of particle-tracking Individual-Based Models (IBM) coupled to a 3D Princeton Ocean Model (POM). The hydrodynamic model was forced with in situ data obtained from January 2000 to December 2010. The IBM-POM models considered two transport scenarios: (1) passive Lagrangian transport and (2) Diel Vertical Migration (DVM). Results suggest that retention on actual and putative nursery grounds is high, and may retain paralarvae in a suitable environment for survival, growth and ultimately to recruit to the adult population. Taking in account a nine months lifespan for de species, plotting of autumn-winter retention indexes against spring-summer industrial and artisanal landings in the following year showed high correlation, and this can hold promise for forthcoming adult biomass prediction.

 

Cephalopod International Advisory Council Conference, 2018, St Petersburg. Cephalopod Research Across Scales: From Molecules to Ecosystems, 2018. p. 55.

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Rézio, A.T., Ávila-da-Silva, A.O., Pimenta, F.M., Camargo, R., Martins, R.S. 2018. Recruitment failure of the tropical arrow squid Doryteuthis plei linked to anomalous oceanographic conditions during the spawning season
Recruitment failure is a remarkable phenomenon in most cephalopod fisheries. This is due their short life cycle associated to semelparity, and the reliance on paralarval survivorship to ensure spatial and temporal continuity of cephalopod populations. Recruitment failures have been detected at least four times over the last 17 years for the tropical arrow squid (Doryteuthis plei) off southern Brazil (22–29°S). Bearing in mind the vulnerability of paralarvae to unsuitable environmental conditions, this study aims to investigate the possible causes of such failures using publicly available catches (tonnes landed) and satellite products data (namely, sea surface temperature, sea surface salinity, sea surface chlorophyll and wind fields) recorded on shelf waters off southern Brazil. Based on a 9-month life cycle, it is hypothesized that anomalous abiotic conditions during austral autumn-winter may lead to recruitment failure in the following spring-summer (the main harvest season for the species). Results will allow a better understanding on the causes of natural population fluctuations for the species.

 

Cephalopod International Advisory Council Conference, 2018, St Petersburg. Cephalopod Research Across Scales: From Molecules to Ecosystems, 2018. p. 102.