Postuma, F. A., and Gasalla, M. A. 2010. On the relationship between squid and the environment: artisanal jigging for Loligo plei at São Sebastião Island (24°S), southeastern Brazil. – ICES Journal of Marine Science, 67: 1353–1362. The squid Loligo plei concentrates in the southeastern Brazil Bight, where it has traditionally supported small-scale fisheries around São Sebastião Island (SSI). Sea surface temperature (SST), chlorophyll-a (Chl a), windspeed, wave height, rainfall, and lunar phase are related to fishing records and to the results of a survey of local fishers to investigate how they believe environmental variables might affect catches of L. plei. Daily fishery-dependent data over the years 2005–2009 were obtained from a fishing cooperative and were matched with satellite and meteorological forecast data. Generalized linear models were used to explore the significance of environmental variables in relation to variability in catch and catch per unit effort (cpue). Squid are fished with jigs in water shallower than 20 m, generally where SST is warmer and Chl a and windspeed are lower. Cpue and monthly catches decreased from 2005 to 2008, followed by a slight increase in 2009. The correlations between fishery and environmental data relate well to fishers' oceanological knowledge, underscoring the potential of incorporating such knowledge into evaluations of the fishery.

Gasalla, M. A., Rodrigues, A. R., and Postuma, F. A. 2010. The trophic role of the squid Loligo plei as a keystone species in the South Brazil Bight ecosystem. – ICES Journal of Marine Science, 67: 1413–1424. The issue of whether loliginid squid can influence the average structure of marine ecosystems in a keystone role, i.e. a strong effect with relatively low biomass, has not yet been examined. Here, the diet of Loligo plei in inner shelf waters of the South Brazil Bight was examined, as a first step, based on the stomach contents of 2200 squid hand-jigged in shallow water (<30 m) and taken as bycatch of shrimp trawlers in deeper water (30–100 m). Diet varied by size, season, and fishing zone. Stomachs were not empty in ∼12%, with more empty during winter. The range of mantle lengths of squid caught by jigging (101–356 mm) appeared to differ from the squid trawled (30–236 mm), and the diet also differed. Food categories recorded in deeper water did not include amphipods or polychaetes, but in both fishing areas, fish were the most common prey. The fish prey identified included Trachurus lathami, small pelagic species, trichiurids, and Merluccius hubbsi. Demersal species, such as Ctenosciaena gracilicirrhus, and flatfish were also present. An ecosystem network model is updated through which a mixed-trophic impact matrix and “keystoneness” indicators were calculated. Loligo plei represents an important link between pelagic and demersal energy pathways, with high indices of keystoneness.

Variações temporais da captura de recursos pesqueiros estão relacionadas à(s): (1) disponibilidade dos mesmos e a outros fatores oceanográficos, (2) respostas dos estoques pesqueiros às remoções geradas pela pesca, (3) alteração na estrutura das comunidades derivadas de ações antrópicas, e (4) mudanças nas decisões dos pescadores, como escolha dos portos de desembarque e evolução do interesse comercial. Sua análise é fundamental para monitorar mudanças ou alterações nas pescarias e nos ecossistemas marinhos. A pesca de cefalópodes loliginídeos (lulas) ocorre em ecossistemas costeiros e de plataforma continental, e representa importância crescente na costa Sudeste do Brasil, onde concentrações significativas de Loligo plei e Loligo sanpaulensis representam recursos pesqueiros costeiros potenciais (Costa & Haimovici, 1990, Pérez, 1999, Gasalla & Marques, 2000). Artesanalmente, as lulas são capturadas no verão, junto a ilhas costeiras, através de linha-de-mão com zangarilhos, em pequenas embarcações. De forma industrial, estes recursos ocorrem como fauna acompanhante ou captura acessória da frota pesqueira, principalmente a de arrasto-de-fundo.

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Squids can express several body patterns, aided by a variety of visual signals that are produced by chromatophore organs. However, for several squid species, body patterning behavior during reproductive activity is still not completely understood. For example, what are the specific patterning changes and other visual signals, how do they appear, and how long do they last? To test the hypothesis that distinct chromatic components appear at different durations on the skin of the tropical arrow squid Doryteuthis plei in the Southern Hemisphere, we identified and described its body patterning behavior. Specimen squids were obtained from off the South Brazil Bight, near the coast of the São Paulo shelf. Animals were maintained and monitored in circular tanks for 62 d over six observation periods, from 2011 through 2013. An ethogram was constructed showing 19 chromatic, 5 locomotor, and 12 postural components, or body patterns, associated with reproductive behavior. New chromatic components (i.e., those not yet reported in the North Atlantic D. plei species), particularly those linked to female sexual maturity, were observed. A postural component, the "J-Posture," linked to defenses and alarm, also was noted. The average time spent for "light" components was 32 s. The corresponding "dark" components had an average duration of 28 s. Females displayed the chromatic components related to calm behavior longer than males. However, males appeared to be more dedicated to disputes over resources, and used rapid, miscellaneous visual signaling. In conclusion, new basic types of body patterns are described for D. plei. The repertoire of chromatic components reported in the ethogram is, to our knowledge, the first record for D. plei of the Southern Hemisphere.

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This PhD thesis addresses several aspects of the biology and ecology of the squid Doryteuthis plei in the coast of São Paulo, SE Brazil, at both the population and individual levels. On the population structure of the exploited stock, it includes the patterns of reproductive activity, size-at-maturity, and biometrics of reproductive organs associated with squid size, as well as feeding habits and ontogenetic, sexual, and spatial-temporal shifts. Generalized Additive Models for Location, Scale, and Shape (GAMLSS) were used to identify such population patterns and spatial and temporal factors based on the particular small-scale fishery that targets the species around the São Sebastião Island. At the individual level, the study focused on behavioural traits in two periods of the life-cycle: (1) the reproductive phase, where the body patterns were described, generating a comprehensive ethogram for the species, and (2) the paralarval phase, where the development of swimming and predatory behaviours was detailed. Size-at-maturity was found to be 151-175 mm of mantle length (ML) for females, and 187-190 mm ML for males, that also showed the co-occurrence of two distinct maturation groups (Chapter 1). A significant peak of females gonad weight occurs in February and March especially in the island's South and Southeastern areas, and of males in March. An ethogram analysis showed 19 chromatic, 5 locomotor, and 12 postural components and behavioural sequences for the species, including agonistic, courtship, and mating behaviour (Chapter 2). Light chromatic components (clear and iridophore splotches) showed a longer duration than dark chromatic components, especially those associated with calm behaviour, more frequent in females. Males appeared more dedicated to disputes over resources and used fast miscellaneous visual signalling. In respect to feeding habits (Chapter 3), prey composition differed among sexes, size, maturity, and spatio-temporal pattern. Females do not stop feeding during sexual maturation and the amount of food increases with size. Cephalopods were significant preys for mature females, as well as fish and crustaceans to the largest females, while pelagic polychaetes were dominant prey for largest males. Observations and filming of D. plei paralarvae (Chapter 4) show a complex predatory behaviour on live preys, with different hunting types differing in speed and position. Aggressive intra-specific behaviour was found in the absence of prey when paralarvae show both a pursuit strategy and a rapid backward escape after attack. These findings contribute to better understand the population biology and behavior of the species and also in the future definition and guidance of fisheries management plans.