Academic literature on the topic 'Nototodarus'

Size of ripe eggs and potential fecundity are described in the squid of the subfamilies Todaropsinae and Todarodinae (Oegopsida: Ommastrephidae)—Todaropsis eblanae from West Africa, Todarodes angolensis from Namibia, Todarodes sagittatus from north-west Africa and the Mediterranean Sea, Todarodes sp. from the south-east Pacific, Nototodarus hawaiiensis from the south-east Pacific and West Indian Ocean and Martialia hyadesi from the south-west Atlantic. Females of both subfamilies are characterized by a wide range of ripe egg size (0.7–2.4 mm) and low and medium values of potential fecundity (20,000–2,500,000).

Allozyme differentiation was investigated at 23 putative enzyme coding loci in 16 ommastrephid squids to identify species and to assess genetic relationships. The species examined were Illex illecebrosus, I. coindetii, I. argentinus, Todaropsis eblanae, Todarodes sagittatus, T. angolensis, T. filippovae, T. pacificus pacificus, Nototodarus sloanii, N. gouldi, Martialia hyadesi, Ommastrephes bartramii, Sthenoteuthis pteropus, S. oualaniensis, Eucleoteuthis luminosa, and Dosidicus gigas. A dendrogram based on Nei's genetic distance between the species closely approximates to the latest systematics based on morphological characters, but the positions of M. hyadesi and T. eblanae were considerably distant from all other species. The results demonstrate the benefits of further biochemical analysis to an understanding of the systematics of the ommastrephid squids.

The importance of feeding pattern is well documented in fish (Jenkins & Green, 1977; Simenstad & Cailliet, 1986) but there are not many reported studies in cephalopods. Feeding patterns, as defined by Jenkins & Green (1977) have been studied, to our knowledge, only in Todarodes pacificus (Okiyama, 1965), Loligo pealei (Vovk, 1972), Loligo opalescens (Karpov & Cailliet, 1978), Illex illecebrosus (Amaratunga et ah, 1979; Amaratunga, 1980) and Nototodarus gouldi (O'Sullivan & Cullen, 1983). Boyle (1983) dealt with aspects of feeding in several cephalopod species but not specifically with feeding pattern. Aspects of feeding in Sepia officinalis have been reviewed by Nixon (1987). The present work describes the daily feeding pattern in Sepia officinalis from data collected in the field.

In Tasmanian waters, Arctocephalus pusillus doriferus preyed on 11 species of cephalopods, predominantly Nototodarus gouldi followed by Sepioteuthis australis and Sepia apama. Cephalopods were more important in the diet of the seals in Bass Strait than in southern Tasmanian waters. The species composition in the diet of the seals in these two areas also differed, with the seals in Bass Strait eating mainly N. gouldi, whereas the seals in southern waters fed on benthic octopods. The seals preyed on mainly adult cephalopods over the continental shelf. The size range and species composition of the diet varied according to the sample types, with faeces containing only small beaks relative to regurgitates and stomachs. Errors associated with sample types and application of regression equations are discussed.

This study details the feeding ecology of arrow squid,Nototodarus gouldi, collected opportunistically from trawlers in waters south-east off Australia in 2007 and 2008. Combined stomach content and fatty acid (FA) signature analyses provided clear evidence of seasonal dietary shifts in prey composition. Teleost fish remains (mainly otoliths) were found in 67% of stomachs with the two mesopelagic planktivorous fish,Lampanyctodes hectorisandMaurolicus muelleridominating. Cephalopods and crustaceans were supplementary dietary components, with an increased representation in the diet over winter. Digestive gland lipid content was moderate (16.4 ± 8.4% wet weight) and was rich in triacylglycerol and monounsaturated fatty acids. Multivariate analysis of FA profiles grouped arrow squid with profiles of mesopelagic fish and cephalopods, thus supporting the findings of stomach content analysis. Seasonal differences in total lipid content were likely related to summer upwelling events and local changes in productivity, while intraspecific differences in lipid class and FA composition were related to seasonal differences of prey consumption. FA analyses also demonstrated dietary differences associated with gender, size and female maturation. Such relationships demonstrate that the diet ofN. gouldiis closely linked to prey size, abundance and availability and possibly also, to key life-history stages.

AbstractAllozyme electrophoresis was used to examine the stock structure of arrow squid Nototodarus gouldi (McCoy 1888) from Australia. Samples collected from six localities around southern Australia, separated by distances of between 700 and 4300 km, were examined for allozyme variation at 48 loci. The data revealed no evidence of more than a single species among the 203 squid examined. Nine polymorphic loci were detected, although only three were sufficiently variable to provide real insight into the population structure of arrow squid. There were no significant deviations from Hardy–Weinberg expectations for any locus, population, or for the metapopulation. Pairwise comparisons of allele frequencies revealed minor evidence of stock structure, with the Iluka (north New South Wales) sample set displaying significant allelic differences from the Tasmanian sample set at Acyc and from the Ulladulla (south New South Wales) sample set at Sordh. F-statistics also provided weak support that the Australian metapopulation is not panmictic. Further studies are needed to delineate the degree of stock segregation within the Australian/New Zealand region in order to successfully manage the arrow squid fishery in these waters.

Nototodarus sloanii is an important component of the Southern Ocean fauna, and the basis of a large commercial fishery. Despite this, much is unknown about the biology of this species. This study examines some aspects of the biology of N. sloanii. Stomach contents analysis identified no significant differences in diet between male and female squid. Sixteen putative species, including 12 identifiable teleosts, 2 crustaceans, and 2 cephalopods were identified in the diet of this species. The euphausid, Nyctiphanes australis was the most important prey item, Lanternfish, Lampanyctodes hectoris, and Pearlside, Maurolicus muelleri, were of secondary importance. Squid were aged using counts of statolith micro-increments and back-calculation from the date of capture showed that hatching occurred between August and February, with a peak in the austral winter/spring and another smaller peak in the austral summer. Growth rate for male squid differed depending on whether squid were hatched in the winter/spring or summer. Growth rates were more variable in the winter/spring-hatched individuals, and they attained larger size than summer-hatched squid. This was not the case for female squid. Mean age for immature winter/spring-hatched squid was significantly higher than for summer-hatched squid, although there was no significant difference in mean mantle length or body mass. No significant differences between mean age, mantle length, or body mass for same-gender mature squid, regardless of hatch season, were apparent. However, mature female squid hatched in the winter/spring season were significantly longer (ML) than mature male squid hatched in winter/spring. No squid was found to be older than 211 days. All squid had started to mature by 91-120 days old and all were fully mature at 180 days. Validation experiments run on juvenile squid using calcein markers were inconclusive, however the increments in the statoliths were very similar to those found in other validated species of ommastrephid squid, thus for the purposes of this study they were assumed to be of daily periodicity. Gladius increments identify a gender difference in growth rate, with female squid having a shorter initial slow growth phase than male squid. Gonadosomatic indices (GSIs) were calculated for male and female squid. These were low (7.12%�0.3% for females and 1.9%�0.2% for males) suggesting that these squid are intermittent spawners. This is further supported by a histological examination, which found germinal cells of different stages present in the same gonad. Lack of mature individuals in this study means that these results are suggestive rather than definitive; more examination of the reproductive process of this squid is required. Histological examination was also used to validate the Lipinski maturity scale for use with this species, while some misidentification occurred the scale is useful to place squid into the broad categories of immature, maturing, or mature. New maturity scales were created for N. sloanii utilising these broad categories. Finer-scale identification is not possible using this scale, as maturation appears to be a continuous process. Morphometric measurements were taken from both hard and soft tissues and were analysed using non-metric multidimensional scaling and analysis of similarity. Divisions were only apparent in the hard structure measurements. They did not appear to be age, dietary or reproductive differences.

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia
No Oceano Austral, os cefalópodes têm um papel muito importante nas redes tróficas onde os pinguins se alimentam deles. O pinguim das Snares, Eudyptes robustus, é uma espécie endémica das Ilhas das Snares, Nova Zelândia. Estes foram usados como amostradores biológicos para avaliar a componente de cefalópodes na sua dieta na região das Ilhas Snares e para avaliar o tipo de habitat e nível trófico que os cefalópodes ocupam (através de análise de isótopos estáveis dos bicos). O pinguim das Snares está classificado como “vulnerável” de acordo com a Conservação da Natureza e dos Recursos Naturais (IUCN), devido ao facto de terem um habitat restrito e serem suscetíveis a atividades antropogénicas. Dados da dieta desta espécie são historicamente escassos e, como tal, procedi a uma análise detalhada da sua dieta durante o período reprodutor de 1986/87 (Novembro a Fevereiro). Os resultados demonstraram que se alimenta de três espécies diferentes de cefalópodes (Nototodarus sloanii, Onykia ingens, e Octopus campbelli) (998, 1221 e 294 bicos, respetivamente, de 36 amostras). Todos os indíviduos das três espécies eram juvenis, mas os de N. sloanii (tamanho médio do manto (ML) = 128.9 mm; massa média (M) = 63.7 g) eram maiores que os de O. ingens (ML = 73.9 mm; M = 23.6 g) e maiores que os de O. campbelli (ML = 0.4 mm; M = 0.6 g). Pela frequência de ocurrência e massa, N. sloanii foi a espécie mais importante (F% = 97.2; M% = 72.5) e O. ingens a mais importante em número (N% = 48.6). Mattern, et al. (2009) descreveu uma alta diversidade de cefalópodes na dieta de pinguins das Snares nas amostras recolhidas no período reprodutor de 2002, de Outubro a Novembro (N = 11 taxa versus 3 espécies no meu estudo). As espécies mais importantes em ambos os estudos foram as mesmas (N. sloanii e O. ingens). É de frisar que Mattern, et al. (2009) descreveu a presença de Histioteuthis atlantica, lula associada a águas quentes, e a presença da espécie pelágica de polvo Ocythoe tuberculata, ambos numericamente relevantes. Estes resultados sugerem que os pinguins das Snares talvez procuraram o seu alimento em águas mais pelágicas nos anos 2000 do que na década de 80. Através da análise de isótopos estáveis, o meu estudo demonstrou que as espécies, N. sloanii e O. ingens, ocupavam um habitat similar (média δ13C ± SD; -17.8 ± 0.2, -17.4 ± 0.5, respetivamente) na plataforma continental das Ilhas das Snares, mas a espécie de polvo O. campbelli ocupava um habitat mais a sul (-18.5 ± 0.3). Além disso, O. campbelli consumiu presas de nível trófico mais elevado (média δ15N ± SD; 6.7 ± 0.5) quando comparado com as espécies de lula N. sloanii e O. ingens (4.8 ± 0.9, 4.3 ± 0.9, respetivamente). O. campbelli é uma espécie de polvo bêntica e, num sistema bêntico de reciclagem de nutrientes, este é tipicamente melhorado sendo traduzido em elevados valores de δ15N na base da cadeia trófica.As espécies de cefalópodes O. ingens e O. campbelli foram ambas descritas na dieta de pinguins das Snares, assim como na dieta de pinguins Eastern Rockhopper (Eudyptes chrysocome filholi) (Ilhas Campbell). Os valores de δ13C de O. ingens diminuiram de -17.6 ± 0.5 (Ilhas Snares) para -18.8 ± 0.8 (Ilhas Campbell, mais a sul), sugerindo que estes indivíduos não eram da mesma população. Comparando os valores de δ13C de O. campbelli (-18.5 ± 0.3) das Ilhas Snares com os valores das Ilhas Campbell (-18.8 ± 0.6), estes indivíduos eram provavelmente da mesma população, sugerindo que os pinguins das Snares talvez tivessem procurado as suas presas mais a sul em águas Sub-Antárticas próximas da Ilha de Campbell. Quanto ao nível trófico (δ15N) de O. ingens, esta lula predada por pinguins das Snares (4.3 ± 0.9) teve um nível trófico idêntico ao da lula O. ingens predada pelos pinguins Eastern Rockhopper (4.4 ± 0.6). Isto sugere que ambos os indivíduos tinham dietas similares. O nível trófico de O. campbelli consumido por pinguins das Snares apresentou valores mais elevados (6.7 ± 0.5) quando comparados aos pinguins Eastern Rockhopper (4.4 ± 0.8), inferindo que provavelmente estes indivíduos de O. campbelli tinham dietas diferentes.Em relação às pescas locais de cefalópodes, a lula N. sloanii já era alvo de pescas comerciais na década de 80 na plataforma continental das Snares, onde indivíduos de tamanho maior (ML: 150-386 mm) eram pescados em comparação àqueles que foram descritos na dieta dos pinguins das Snares, mesmo que haja uma sobreposição das áreas de pesca e nas áreas de forrageamento dos pinguins das Snares. Desde os anos 80, as pescas locais ocurrem durante o período reprodutivo dos pinguins das Snares, mas como estes só se reproduzem nas Ilhas das Snares, a 200 km a sul da Nova Zelândia, o risco desta espécie interagir com pescas é baixo quando comparado com outras espécies de pinguim, embora não deva ser menosprezado. Mais, as alterações climáticas podem vir afetar a disponibilidade de presas, incluindo cefalópodes, tornando-se numa ameaça real num futuro próximo.
In the Southern Ocean and adjacent waters, cephalopods play an important role in food webs where penguins are known to feed considerably on them. The Snares penguin, Eudyptes robustus, an endemic penguin species from Snares Islands, New Zealand, was used as a biological sampler to evaluate the cephalopod component of the diet of penguins around the Snares Islands and assess the habitat and trophic level of cephalopods (through stable isotope analyses of beak material). Snares penguin is classified as “vulnerable” according to the International Union for Conservation of Nature (IUCN) due to its restricted habitat and susceptibility to anthropogenic activities. As historical diet data is rare for this species, I carried out detailed analyses of the diet of Snares penguins in the breeding season 1986-87 (Nov.-Feb.). The results show that penguins feed on three cephalopod species (Nototodarus sloanii, Onykia ingens, and Octopus campbelli) (998, 1221 and 294 beaks, respectively, from 36 samples). All cephalopod specimens were juveniles, with N. sloanii (mean mantle length (ML) = 128.9 mm; mean mass (M) = 63.7 g) individuals being larger than O. ingens (mean ML = 73.9 mm; mean M = 23.6 g) and O. campbelli (mean ML = 0.4 mm; mean M = 0.6 g). By frequency of occurrence and mass, N. sloanii was the most important species (F% = 97.2; M% = 72.5) and O. ingens was the most important species by number (N% = 48.6). Mattern et al. (2009) found a higher diversity of cephalopods in the diet of Snares penguins in samples collected in Oct.-Nov. 2002 (N = 11 taxa versus 3 species in our study). The most important cephalopod species were the same in both studies (Nototodarus sloanii and Onykia ingens). Also, Mattern et al. (2009) found Histioteuthis atlantica, which is a squid associated with warm waters, and the pelagic octopod Ocythoe tuberculata, both still numerically relevant. These results suggest that Snares penguins may forage more in pelagic waters in the 2000’s than in 1980’s. According to stable isotope analysis, our study revealed that squid species, N. sloanii and O. ingens, occupied similar habitats (mean δ13C ± SD; -17.8 ± 0.2, -17.4 ± 0.5, respectively) on the continental shelf of Snares Islands, whereas the octopod species O. campbelli occupied a southern habitat (-18.5 ± 0.3). Moreover, O. campbelli feed on significantly higher trophic level prey (mean δ15N ± SD; 6.7 ± 0.5) when compared to N. sloanii and O. ingens (4.8 ± 0.9, 4.3 ± 0.9, respectively). O. campbelli is a benthic octopod and, in a benthic system, recycling of nutrients is typically enhanced, which usually translates into elevated δ15N values at the base of the trophic chain.The cephalopod species O. ingens and O. campbelli occurred both in the diet of Snares penguins and Eastern Rockhopper penguins (Eudyptes chrysocome filholi) (Campbell Islands). The δ13C values of O. ingens decrease from -17.6 ± 0.5 (Snares Islands) to -18.8 ± 0.8 (Campbell Islands, more south), suggesting that these individuals were not from the same population. Comparing δ13C values of O. campbelli (-18.5 ± 0.3) in Snares Island with the values from Campbell Island (-18.8 ± 0.6), the individuals were probably from the same population, as Snares penguins may have foraged more south to Sub-Antarctic waters, near at Campbell Island. Regarding the trophic level (δ15N) of O. ingens, this squid consumed by Snares penguins (4.3 ± 0.9) was of similar trophic level as O. ingens consumed by Eastern Rockhopper penguins (4.4 ± 0.6), suggesting that both individuals had similar diets. The trophic level of O. campbelli consumed by Snares penguins had bigger values (6.7 ± 0.5) compared to Eastern Rockhopper penguins (4.4 ± 0.8), inferring that perhaps O. campbelli had different diets.From a conservation perspective, in relation to local cephalopod fisheries, N. sloanii was already a target species in the 1980´s at the Snares Continental Shelf, catching bigger size squid (ML: 150-386 mm) than those found in the diet of Snares penguins, despite the high overlap between fishing and foraging areas. As in the 1980’s, nowadays local fisheries occur during Snares penguins breeding season, but as they breed only at Snares Islands (200 km south of the mainland), the risks of this species to interact with fisheries is lower when compared to other species, but can’t be overlooked. Climate change, which may affect the future availability of penguin prey, including cephalopods, might be a real threat in a short-term future.