Topic
Illex
About: Illex is a research topic. Over the lifetime, 93 publications have been published within this topic receiving 1905 citations.
Papers published on a yearly basis
Papers
TL;DR: Post-recruit Illex argentinus were collected from the fishery on the Patagonian Shelf between 1986 and 1988, and age was determined by analysis of daily growth increments in ground sections of the statolith, female fecundity was determined, specimens were dissected, weighed and assigned a maturity stage.
Abstract: Post-recruit Illex argentinus were collected from the fishery on the Patagonian Shelf between 1986 and 1988. Age was determined by analysis of daily growth increments in ground sections of the statolith, female fecundity was determined, specimens were dissected, weighed and assigned a maturity stage. The relation between mantle length and age is best approximated by a linear model. Both sexes live approximately one year. Females grow faster and attain a larger size than males, but males mature younger. Hatching occurs during the austral winter, peaking in June-July. There is a consistent trend of increasing growth rate with later date of hatching. Statolith growth is negatively allometric with body growth and there is greater divergence between statolith and body growth in females. In post-recruit Illex growth in mass of somatic tissues, apart from the digestive gland, approximates isometry with growth of the whole body. Growth of the digestive gland and the reproductive organs is positively allometric with growth in whole body mass. There is poor correlation between the female reproductive organs and whole body mass, which is due to differences in size at maturity. Mating rarely occurs on the feeding grounds. Fecundity of fully mature females in the sample falls in the range 113835-246098 eggs per individual. This possibly underestimates average fecundity because mature squid on the feeding grounds may be precocious and smaller than average at full maturity. A model combining absolute and relative growth, predicts average male and female growth and growth of the major somatic and reproductive organs. This poorly predicts average female maturity indices with age because of variability in mass of the female reproductive organs. A model that treats maturity stages separately gives close agreement with measured mass of the reproductive organs and maturity indices of a mature female at age one year. Females invest approximately 20% of total body mass in gonad and accessory reproductive organs at full maturity.
111 citations
Book•
1 Jan 1998
TL;DR: Detailed understanding of stock structure and highly variable recruitment dynamics is required to ensure conservation of the resource base and achieve sustainability of directed fisheries.
Abstract: Squid are among the fastest-growing short-lived commercial species and, as opposed to most finfish resources worldwide, their contribution to the total world fish production has been increasing at a high rate in the two last decades. Also, since squids tend to have higher global market values than many fish, they have the potential to produce both larger and more valuable catches, given the same level of primary productivity. As annuals, ommastrephid squid, like those in the genus Illex used as an example in this volume, grow rapidly with high production to biomass ratios, but have no reserves of genetic diversity once a year class is overfished. Thus, detailed understanding of stock structure and highly variable recruitment dynamics is required to ensure conservation of the resource base and achieve sustainability of directed fisheries. Increment analysis for age and growth, and stomach content analysis, indicate flexible seasonality and feeding strategies allowing a wide range of habitats. I. coindetii occupies the Mediterranean, Caribbean and eastern Atlantic margin from 55°N to 20°S but never sustains major fisheries. In the western boundary currents of the Atlantic, I. illecebrosus collapsed after intense, widely distributed fishing in the north, while, in the south, I. argentinus has survived much longer as the world's largest squid fishery, possibly stabilized by a complex of stocks, with widely dispersed breeding in space and time. Selective gears in feeding areas may be self-limiting, so long as migration ensures adequate escapement and the squid are not pursued into breeding areas. Recruitment appears to be limited by food production and by instabilities in the interactions between adult migrations and ocean physics, which strongly influence early growth and survival. After chapters reviewing the principal commercial species of Illex, both techniques and results of studies on these influencing factors are reported in separate chapters by experts in their fields.
107 citations
TL;DR: The strict dependence of Magellanic Penguins on commercially-exploited, schooling prey species makes the species particularly susceptible to changes in prey stocks, as has happened to congeners elsewhere that have suffered population crashes due to poorly-managed fisheries.
Abstract: -The diet of Magellanic Penguins (Spheniscus magellanicus) was studied by stomach-pumping birds at five colonies (San Lorenzo, Punta Clara, Punta Loberia, Monte Leon and Punta Dungeness) over the species' latitudinal range in Argentina. A total of 159 birds were sampled during the period February 1986 to December 1988. Most prey items consisted of pelagic school fish, although squid and shrimps were also taken. At any one colony, birds appeared to be principally monoor bi-phagic and there were clear latitudinal differences in prey taken. Penguins in the northern colonies at San Lorenzo, Punta Clara and Punta Loberia consumed primarily anchovy (Engraulis anchoita) while birds at the two southerly colonies of Monte Leon and Punta Dungeness fed primarily on squid (Loligo spp. and Illex spp.), sprats (Sprattusfuegensis) and Hagfish (Myxine spp.). The strict dependence of Magellanic Penguins on commercially-exploited, schooling prey species makes the species particularly susceptible to changes in prey stocks, as has happened to congeners elsewhere that have suffered population crashes due to poorly-managed fisheries. Received iiJanuaryl 999, accepted 24 February 1999.
89 citations
TL;DR: There was a difference in the size-frequency distribution of the cephalopod diet in the two years; in 1984 there was a higher frequency of intermediate-sized specimens, reflecting the greater importance of ommastrephids, especially Illex sp.
Abstract: Cephalopod beaks from the stomach contents of “wandering albatross” (Diomedea exulans L) chicks from Bird Island, South Georgia, were sampled between May and September in 1983 and 1984 Lower beaks were identified and measured, and allometric data were used to calculated mantle length and biomass of the species consumed A total of 3421 lower beaks were examined, representing 35 species in the 1983 sample and 45 species in the 1984 sample Eight of the twenty families contributed over 95% of the biomass In 1984 there were less Onychoteuthidae and more Ommastrephidae than in 1983 and a decrease in the number of species known to occur south of the Antarctic Polar Front There was a difference in the size-frequency distribution of the cephalopod diet in the two years; in 1984 there was a higher frequency of intermediate-sized specimens, reflecting the greater importance of ommastrephids, especially Illex sp The energy content of cephalopods in 1984 may have been greater than in 1983 Serial sampling of cephalopod beaks during the austral winter did not reveal evidence of growth By the age of 200 d, wandering albatross chicks have consumed a total of approximately 100 kg wet weight of cephalopods each
87 citations
TL;DR: The squids genus Illex is one of typical r-strategists among the cephalopods and ripe egg production decreases over time with only a 50% replacement of the initial stock of vitelline oocytes and a decreasing volume of eggs at each release.
Abstract: Ripe egg dimensions in the squid genus Illex are close to the minimum for cephalopods. The average diameter varies significantly depending on species (0.77–0.82 mm in I. coindeti , 0.75–0.88 mm in I. illecebrosus , and 0.96–1.04 mm in I. argentinus ), on geographical distribution intraspecifically, e.g. I. argentinus (0.96–0.97 mm in the shelf groups and 1.04 mm in the slope oceanic group), and between pre-spawning and spawning females of the summer-spawning shelf group of I. argentinus (0.97 and 0.92 mm, respectively). The potential fecundity (PF), defined as total oocyte stock both in the ovary and oviducts, depends on mantle length (ML in each species. It varies from 90 000 (ML = 150–160 mm) to 800 000 (ML = 230–250 mm) in I. coindeti , from 200 000 to 630 000 (ML = 220–280 mm) in I. illecebrosus , and from 75 000 (ML = 150–170 mm) to 1 200 000 (ML = 360–380 mm) in I. argentinus . It is possible to estimate the actual value of PF shortly before vitellogenesis begins and up to a start of spawning, when the diameter of the smallest oocytes exceeds 0.05 mm. The summer-spawning shelf females of I. argentinus release about of 70% of PF. Their spawning is intermittent and ripe egg production decreases over time with only a 50% replacement of the initial stock of vitelline oocytes and a decreasing volume of eggs at each release. Feeding activity decreases and the mantle wall and internal organs shrink once spawning commences. In spent animals, a degeneration of both vitelline and protoplasmic oocytes occurs. The squids genus Illex is one of typical r-strategists among the cephalopods.
86 citations
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| Year | Papers |
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| 2020 | 2 |
| 2017 | 1 |
| 2016 | 2 |
| 2015 | 1 |
| 2014 | 1 |
| 2013 | 1 |