DOCSLIB.ORG

Interannual Variation in Life-Cycle Characteristics of the Veined Squid (Loligo Forbesi). ICES CM 2004/CC:31

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Interannual Variation in Life-Cycle Characteristics of the Veined Squid (Loligo Forbesi). ICES CM 2004/CC:31 Not to be cited without prior reference to the authors ICES CM 2004/CC:31 Interannual variation in life-cycle characteristics of the veined squid (Loligo forbesi) G.J. Pierce, A.F. Zuur, J.M. Smith, M.B. Santos, N. Bailey & P.R. Boyle The loliginid squid Loligo forbesi has a flexible life-cycle, involving variable size and age at maturity, presence of summer and winter breeding populations, and extended periods of breeding and recruitment. This paper reviews life history data collected since 1983 from the commercial fishery in Scottish (UK) waters and examines (a) the relationship between size and timing of maturation, (b) evidence for shifts in the relative abundance of the summer and winter breeding populations, and (c) the role of environmental signals in determining the timing of breeding. Evidence from fishery data suggests that, since the 1970s, the summer breeding population has declined while the winter breeding population now dominates and breeds later than was previously the case. Length-weight relationships and size at maturity showed significant inter-annual and seasonal variation during the period 1983-2001 and provide no evidence that there is currently a summer breeding population. Males are shown to decline in relative weight as they mature while females increase in relative weight. There is evidence that timing of breeding and size at maturity are related to environmental variation (winter NAO index). Key words: life history, time series, environmental factors G.J. Pierce, J.M. Smith, M.B. Santos, P.R. Boyle: University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UK [tel: +44 1224 272866, fax: +44 1224 272396, e-mail: [email protected]]. A. Zuur: Highland Statistics Ltd, 6 Laverock Road, Newburgh, Aberdeenshire, AB41 6FN, UK [tel: +44 1358 788177, email: [email protected]]. N. Bailey: Fisheries Research Services, The Marine Laboratory, PO Box 101, Victoria Road, Aberdeen, AB11 9DB, UK [tel: +44 1224 876544, e-mail: [email protected]] INTRODUCTION The veined squid Loligo forbesi has been exploited as a fishery resource around the British Isles for at least 100 years (see Thomas, 1969; Thomas & Davidson, 1972; Howard, 1979; Pierce et al., 1994a). Interest in its biology dates back at least to the 1970s, when Holme (1974) published a short description of the life history of the species in the English Channel. This work already provided some clues as to the complexity of the life-cycle for, although the species was apparently annual, two breeding populations were apparently present, a one breeding in winter and one breeding in summer. In Scottish waters (Figure 1), two PhDs during the second half of the 1980s (Ngoile, 1987; Lum-Kong, 1989) provided further information on life-cycle biology and reproduction. The basic pattern that emerged was of an annual, winter breeding population. However, two peaks of recruitment were seen, in April and in autumn. Further indications of flexibility and/or complexity included evidence of two sizes at maturity (Boyle & Ngoile 1993a), recruitment throughout the year and the possible existence of morphologically distinct “stocks” (Boyle & Ngoile, 1993b) at Rockall and in coastal waters. Further studies (e.g. during several EC-funded research projects) in Scottish waters between 1990 and 2001 focused on distribution and abundance (Pierce et al., 1998, 2001; Waluda & Pierce, 1998; Bellido et al., 2001; Bellido, 2002; Pierce & Boyle, 2003; Zuur & Pierce, 2004; Young et al., in press), stock structure (Pierce et al., 1994 b, c; Brierley et al., 1995; Shaw et al., 1999) and ecology (Pierce et al., 1994d; Collins & Pierce, 1996; Pierce & Santos, 1996; Daly et al,, 2001). However, several studies have also examined development and growth (Yau, 1994; Martins, 1997; Hughes, 1998; Pierce et al., 1999; Craig, 2001; Gowland, 2002) as well as reproduction and recruitment (Pierce et al., 1994e; Boyle et al., 1995; Collins et al., 1997, 1999; Shaw & Boyle, 1997; Challier et al., in press). These studies essentially confirmed the picture established by Ngoile (1987) of an annual life- cycle with a winter breeding peak and two periods of recruitment. However, it is apparent that there are two or three micro-cohorts of Loligo forbesi present in Scottish waters, following different growth trajectories (Collins et al., 1999). It may be argued that some of the apparent variability in life history patterns reflects the persistence of summer and winter breeding populations in various proportions (Zuur & Pierce, 2004): the observed month-to-month pattern of maturation may be interpreted as two periods of recruitment and two periods of maturation. Shaw et al. (1997) confirmed that squid from offshore waters (around Rockall and Faroe) show some genetic differences from the coastal population. Thus, superimposed on the basic annual life-cycle there may be (in addition to individual variation) variation due to presence of winter and summer breeders, inshore and offshore populations, large and small sizes at maturity,. Unlike relatively long-lived fish species, squid populations are not buffered against environmental change by the presence of several age classes: any factor which affects recruitment success has an immediate impact on population size and, potentially, subsequent reproductive success. There is considerable evidence that distribution and local abundance are affected by environmental variation (see above) and we might logically expect recruitment success, growth, fecundity and breeding success to reflect environmental conditions. If the life-cycle of Loligo forbesi does indeed display substantial plasticity, we hypothesize that (a) changes in life-cycle characteristics would be evident over the medium- to long-term and that (b) such changes may occur in response to changing environmental conditions. We now have access to life history and fishery data on the species in Scottish waters collected over more than 15 years. In this paper we examine interannual variation in the relative importance of summer and winter breeding, length-weight relationships, size at maturity and the timing of maturity, and ask whether such variation can be related to environmental signals, notably the North Atlantic Oscillation Index – which provides a general indication of the strength of Atlantic inflow into coastal waters of Scotland. To measure the relative importance of winter and summer breeding, abundance data are needed. Catch-per-unit effort data from commercial trawling may be used as an approximate relative abundance index (see Pierce et al., 1994a; Pierce & Boyle, 2003). It can also be argued that the peak of the fishery is driven by recruitment (see Figure 2, data from Pierce et al., 1994a, e) and is normally 3-4 months ahead of the peak in the proportion of mature animals. Thus by examining interannual trends in the month-to-month pattern of CPUE we may obtain an indication of interannual variation in the importance of winter and summer breeding. A formal analysis of interannual trends in monthly CPUE series was presented in Zuur & Pierce (2004). Here we briefly re-present the same data in terms of the likely interpretation in terms of the timing of breeding. We go on to examine variation in two basic biological variables, weight at length and maturity at length. Weight at length is expected to follow a standard exponential curve. However, we might also expect variation in relation to the process of maturation. Thus, growing gonads may incur a different energetic cost to growing somatic tissue, mature animals may feed less actively, and gonad growth may involve utilisation of some somatic tissues as an energy source. Seasonal variation might also be expected, relating to changers in food availability, although it may be difficult to disentangle this effect from the effect of maturation. Lastly, we may expect year-to-year differences in growth patterns, related to differences water temperature (see Forsythe, 1993) and/or food supply. Maturation is commonly assumed to be size-dependent, with the proportion of animals that are mature typically increasing with body length following a logistic curve. However, maturation may also require a seasonal trigger and/or depend on accumulation of sufficient energy reserves. Thus we might expect to see both seasonal and interannual variation. In the case of both weight and maturity at length, differences are expected between males and females. For example previous studies show that males can mature at smaller sizes than females and may mature slightly earlier in the year (Pierce et al., 1994e; Boyle et al., 1995). If it is possible to tease out interannual differences in weight and maturity at length it might be hypothesised that these could be linked to environmental variation (e.g. larger weight and earlier maturation in warmer years). Another possibility is that there will be a relationship between size and abundance: positive if both parameters represent a response to environmental conditions, negative (at least at high abundance levels) if there is density- dependent competition. The present study aims to test these hypotheses. METHODS (1) Winter and summer breeding Commercial landings of squid (kg) and fishing effort (hours) data for UK-registered fishing vessels landing in Scotland during the period 1970-2000 were extracted from the Marine Laboratory FRS database. Since discarding of Loligo is thought to be minimal (Young et al., In Press), landings are assumed to accurately reflect catches. To obtain a reasonably consistent CPUE index we restricted the extraction to “light” and “heavy” single demersal trawls (henceforth referred to as “trawling”) from ICES areas IVa and VIa (henceforth referred to as “coastal waters”) and calculated an overall monthly CPUE index as total landings divided by total effort. Since 1998, Scottish fishing effort data are considered to be unreliable (A. Shanks, FRS Marine Laboratory, pers. comm.). However, as we will demonstrate, although there is evidence that CPUE in 1999 and 2000 was underestimated, the month-to-month pattern is driven by the landings data and examination of the latter confirmed that the underlying seasonal trend remains well-represented.
Load more

Recommended publications
  • Signs of an Extended and Intermittent Terminal Spawning In
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Digital.CSIC Signs of an extended and intermittent terminal spawning in the squids Loligo vulgaris Lamarck and Loligo forbesi Steenstrup (Cephalopoda: Loliginidae) Francisco Rocha*, Angel Guerra Instituto de Investigaciones Marinas (CSIC), C/ Eduardo Cabello 6, 36208 Vigo, Spain *Corresponding author. Tel.: + 34 86 231930; Fax: +34 86 292762 Abstract The reproductive pattern of Loligo vulgaris and Loligo forbesi was studied on the basis of gonad maturation, mating and spawning in males and females of both species which were present off the northwest coast of Spain (Galicia), between February 1991 and February 1993. The mature females of both species have several modes of egg sizes and developmental stages within the ovary. Several signs indicate that both female Loligo vulgaris and L. forbesi undergo partial ovulation at the time of spawning, the spawning period being relatively long, although in no case representing the greatest fraction of the animal’s life before death. Egg-laying occurring in separate batches and somatic growth between egg batchs has not been observed. This reproductive pattern is defined as intermittent terminal spawning. Some other terms describing different cephalopod reproductive strategies are also defined. Keywords: Loligo forbesi; Loligo vulgaris; NW Atlantic; Reproduction; Spawning patterns 1. Introduction Until recently, it was generally accepted that female cephalopods lay their eggs in one single spawning or in several consecutive ones, with no pause between each, after which they would die by exhaustion (McGowan, 1954; Mangold, 1987; Harman et al., 1989; Mangold et al., 1993).
    [Show full text]
  • 1. Natural History of the Squid
    1. Natural History of the Squid INTRODUCTION Cephalopods in general and squid in particular have been the subject of con- siderable curiosity everywhere that man has become acquainted with the sea. These fast-moving animals possess a number of features usually associated only with verte- brate forms and to practitioners of anthropomorphism they appear to have con- siderable cunning. Popular accounts of these animals are recurrent and only a few wil be mentioned to introduce the subject: Lane (1957) provided a comprehensive and readable coverage of cephalopods in a book slanted toward Octopus; Morton's (1958) introduction to mollusks sets the cephalopods among other members of the phylum; some invertebrate zoology tests, especially one by Russell-Hunter (1968), give good coverage of cephalopods; excellent photographic coverage can be found in articles by Voss and Sisson (1967 and 1971); and behavioral aspects of cephal- opods are summarized in a concise book by Wells (1962). Systematic position Cephalopods are relatively large, active, predaceous mollusks with a high level of nervous development. There are approximately 400 living species which are distributed throughout all marine environments. Fossils of shelled cephalopods are well known and abundant in the Paleozoic and Mesozoic; their direct descendants are almost entirely extinct today, having been replaced by shell-less cephalopods which did not leave a fossil record. Modern forms are subdivided into the Nautiloi- dea (including only the relict genus Nautilus) and the Coleoidea, encompassing the remaining dibranchiate species. The latter are composed of eight-armed forms (Octopoda) and ten-armed forms (Decapoda) which include the true squids (Teu- thoidea) and cuttlefishes (Sepioidea).
    [Show full text]
  • In the Loliginid Squid Alloteuthis Subulata and Loligo Vulgaris
    The Journal of Experimental Biology 204, 2103–2118 (2001) 2103 Printed in Great Britain © The Company of Biologists Limited 2001 JEB3380 REFLECTIVE PROPERTIES OF IRIDOPHORES AND FLUORESCENT ‘EYESPOTS’ IN THE LOLIGINID SQUID ALLOTEUTHIS SUBULATA AND LOLIGO VULGARIS L. M. MÄTHGER1,2,* AND E. J. DENTON1 1The Marine Biological Association of the UK, Citadel Hill, Plymouth PL1 2PB, UK and 2Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK *e-mail: [email protected] Accepted 27 March 2001 Summary Observations were made of the reflective properties of parts of the spectrum and all reflections in other the iridophore stripes of the squid Alloteuthis subulata and wavebands, such as those in the red and near ultraviolet, Loligo vulgaris, and the likely functions of these stripes are will be weak. The functions of the iridophores reflecting red considered in terms of concealment and signalling. at normal incidence must be sought in their reflections of In both species, the mantle muscle is almost transparent. blue-green at oblique angles of incidence. These squid rely Stripes of iridophores run along the length of each side of for their camouflage mainly on their transparency, and the the mantle, some of which, when viewed at normal ventral iridophores and the red, green and blue reflective incidence in white light, reflect red, others green or blue. stripes must be used mainly for signalling. The reflectivities When viewed obliquely, the wavebands best reflected move of some of these stripes are relatively low, allowing a large towards the blue/ultraviolet end of the spectrum and fraction of the incident light to be transmitted into the their reflections are almost 100 % polarised.
    [Show full text]
  • An Illustrated Key to the Families of the Order
    CLYDE F. E. ROP An Illustrated RICHARD E. YOl and GILBERT L. VC Key to the Families of the Order Teuthoidea Cephalopoda) SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1969 NUMBER 13 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 13 Clyde F. E. Roper, An Illustrated Key 5K?Z" to the Families of the Order Teuthoidea (Cephalopoda) SMITHSONIAN INSTITUTION PRESS CITY OF WASHINGTON 1969 SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION The emphasis upon publications as a means of diffusing knowledge was expressed by the first Secretary of the Smithsonian Institution. In his formal plan for the Institution, Joseph Henry articulated a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge not strictly professional." This keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Annals of Flight Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to Zoology Smithsonian Studies in History and Technology In these series, the Institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of professional colleagues at other institutions of learning. These papers report newly acquired facts, synoptic interpretations of data, or original theory in specialized fields.
    [Show full text]
  • Defensive Behaviors of Deep-Sea Squids: Ink Release, Body Patterning, and Arm Autotomy
    Defensive Behaviors of Deep-sea Squids: Ink Release, Body Patterning, and Arm Autotomy by Stephanie Lynn Bush A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Integrative Biology in the Graduate Division of the University of California, Berkeley Committee in Charge: Professor Roy L. Caldwell, Chair Professor David R. Lindberg Professor George K. Roderick Dr. Bruce H. Robison Fall, 2009 Defensive Behaviors of Deep-sea Squids: Ink Release, Body Patterning, and Arm Autotomy © 2009 by Stephanie Lynn Bush ABSTRACT Defensive Behaviors of Deep-sea Squids: Ink Release, Body Patterning, and Arm Autotomy by Stephanie Lynn Bush Doctor of Philosophy in Integrative Biology University of California, Berkeley Professor Roy L. Caldwell, Chair The deep sea is the largest habitat on Earth and holds the majority of its’ animal biomass. Due to the limitations of observing, capturing and studying these diverse and numerous organisms, little is known about them. The majority of deep-sea species are known only from net-caught specimens, therefore behavioral ecology and functional morphology were assumed. The advent of human operated vehicles (HOVs) and remotely operated vehicles (ROVs) have allowed scientists to make one-of-a-kind observations and test hypotheses about deep-sea organismal biology. Cephalopods are large, soft-bodied molluscs whose defenses center on crypsis. Individuals can rapidly change coloration (for background matching, mimicry, and disruptive coloration), skin texture, body postures, locomotion, and release ink to avoid recognition as prey or escape when camouflage fails. Squids, octopuses, and cuttlefishes rely on these visual defenses in shallow-water environments, but deep-sea cephalopods were thought to perform only a limited number of these behaviors because of their extremely low light surroundings.
    [Show full text]
  • Geographic and Temporal Patterns in Size and Maturity of the Longfin Inshore Squid (Loligo Pealeii) Off the Northeastern United States
    Geographic and temporal patterns in size and maturity of the longfin inshore squid (Loligo pealeii) off the northeastern United States Item Type article Authors Hatfield, Emma M.C.; Cadrin, Steven X. Download date 04/10/2021 18:55:59 Link to Item http://hdl.handle.net/1834/31057 200 Abstract–Analysis of 32 years of stan­ Geographic and temporal patterns dardized survey catches (1967–98) indi­ cated differential distribution patterns in size and maturity of the longfin inshore squid for the longfin inshore squid (Loligo pealeii) over the northwest Atlantic (Loligo pealeii) off the northeastern United States U.S. continental shelf, by geographic region, depth, season, and time of day. Emma M.C. Hatfield Catches were greatest in the Mid- Atlantic Bight, where there were sig­ Steven X. Cadrin nificantly greater catches in deep water Northeast Fisheries Science Center during winter and spring, and in National Marine Fisheries Service, NOAA shallow water during autumn. Body 166 Water Street size generally increased with depth Woods Hole, Massachusetts 02543 in all seasons. Large catches of juve­ Present address (for E.M.C. Hatfield): FRS Marine Laboratory niles in shallow waters off southern Victoria Road New England during autumn resulted Aberdeen AB11 9DB from inshore spawning observed during Scotland, United Kingdom late spring and summer; large propor­ E-mail address (for E. M. C. Hatfield): e.hatfi[email protected] tions of juveniles in the Mid-Atlantic Bight during spring suggest that sub­ stantial winter spawning also occurs. Few mature squid were caught in sur­ vey samples in any season; the major­ ity of these mature squid were cap­ tured south of Cape Hatteras during The longfin inshore squid, Loligo pea- mers, 1967; 1969; Serchuk and Rathjen, spring.
    [Show full text]
  • Age and Growth of Two Sympatric Squid Loligo Vulgaris and Loligo Forbesi, in Galician Waters (North-West Spain)
    J. Mar. Biol. Ass. U.K. (1999), 79, 697^707 Printed in the United Kingdom Age and growth of two sympatric squid Loligo vulgaris and Loligo forbesi, in Galician waters (north-west Spain) F. Rocha and A. Guerra Instituto de Investigaciones Marinas (CSIC), Eduardo Cabello 6, 36208 Vigo, Spain Age and growth of Loligo vulgaris and L. forbesi were studied by the examination of growth increments in 96 and 135 selected (white zone 510%) statoliths, respectively. Squid were obtained by monthly sampling from the catches of commercial trawling and hand-jigs in Galician waters (north-west Spain) between February 1991 and October 1993. Mantle length (ML) of L. vulgaris ranged from 70 to 480 mm and varied between 70 and 685 mm in L. forbesi. A negative allometry between statolith length and ML or body weight (BW) was found in both species. Sexual dimorphism was apparent in both species, males grew faster and longer than females. The statolith analysis suggests that growth patterns of L. vulgaris and L. forbesi in Galician waters are di¡erent. The exploited population of L. vulgaris was composed of two groups: one formed by individuals hatched in winter^spring and another by specimens hatched in summer^autumn. Squid hatched in winter^spring reached larger sizes at the same age than those hatched in summer^autumn. These two groups were also observed in L. forbesi. However, squid of this species hatched in winter^spring were smaller than those hatched in summer^autumn at the same age. Reasons for this discrepancy are discussed. The life span of L.
    [Show full text]
  • Lab 5: Phylum Mollusca
    Biology 18 Spring, 2008 Lab 5: Phylum Mollusca Objectives: Understand the taxonomic relationships and major features of mollusks Learn the external and internal anatomy of the clam and squid Understand the major advantages and limitations of the exoskeletons of mollusks in relation to the hydrostatic skeletons of worms and the endoskeletons of vertebrates, which you will examine later in the semester Textbook Reading: pp. 700-702, 1016, 1020 & 1021 (Figure 47.22), 943-944, 978-979, 1046 Introduction The phylum Mollusca consists of over 100,000 marine, freshwater, and terrestrial species. Most are familiar to you as food sources: oysters, clams, scallops, and yes, snails, squid and octopods. Some also serve as intermediate hosts for parasitic trematodes, and others (e.g., snails) can be major agricultural pests. Mollusks have many features in common with annelids and arthropods, such as bilateral symmetry, triploblasty, ventral nerve cords, and a coelom. Unlike annelids, mollusks (with one major exception) do not possess a closed circulatory system, but rather have an open circulatory system consisting of a heart and a few vessels that pump blood into coelomic cavities and sinuses (collectively termed the hemocoel). Other distinguishing features of mollusks are: z A large, muscular foot variously modified for locomotion, digging, attachment, and prey capture. z A mantle, a highly modified epidermis that covers and protects the soft body. In most species, the mantle also secretes a shell of calcium carbonate. z A visceral mass housing the internal organs. z A mantle cavity, the space between the mantle and viscera. Gills, when present, are suspended within this cavity.
    [Show full text]
  • Geographic Drivers of Diversification in Loliginid Squids with an Emphasis on the Western Atlantic Species
    bioRxiv preprint doi: https://doi.org/10.1101/2020.07.20.211896; this version posted July 21, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Original Article Geographic drivers of diversification in loliginid squids with an emphasis on the western Atlantic species Gabrielle Genty1*, Carlos J Pardo-De la Hoz1,2*, Paola Montoya1,3, Elena A. Ritschard1,4* 1Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá D.C, Colombia. 2Department of Biology, Duke University, Durham, North Carolina, 27708, United States of America 3Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Bogotá, D.C., Colombia 4Department of Neuroscience and Developmental Biology, University of Vienna, Austria * These authors contributed equally to this work. Correspondence author: Gabrielle Genty, [email protected] Acknowledgements We would like to thank Daniel Cadena and Andrew J. Crawford for their suggestions and guidance during the early stages of this investigation. bioRxiv preprint doi: https://doi.org/10.1101/2020.07.20.211896; this version posted July 21, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 2 ABSTRACT Aim: Identifying the mechanisms driving divergence in marine organisms is challenging as opportunities for allopatric isolation are less conspicuous than in terrestrial ecosystems.
    [Show full text]
  • Reproductive Cycle of Loligo Sanpa Ulensis (Cephalopoda: Loliginidae) in the Cabo Frio Region, Brazil
    MARINE ECOLOGY PROGRESS SERIES Published November 4 Mar. Ecol. Prog. Ser. Reproductive cycle of Loligo sanpa ulensis (Cephalopoda: Loliginidae) in the Cabo Frio region, Brazil P. A. S. Costa, F. C. Fernandes Instituto de Estudos do Mar Alte Paulo Moreira (IEAPM), Rua Kioto. 253 Arraial do Cabo. 28930-000 Rio de Janeiro, Brazil ABSTRACT. Gonadal index and maturity stages of the Brazilian squid Loljgo sanpaulensjs were analysed on a monthly basis. Squid were caught in coastal waters off the Cabo Frio region, Brazil, between 1987 and 1988 at depths rang~ngfrom 30 to 60 m using an otter trawl with 10 m footrope and 45 mm cod-end mesh size. Field data analysis showed that development of the nidamental gland and testis was closely related (r > 0.9) to body size and maturity stage in the population. Mature indiv~duals are recruited into the population twice a year. Size at first maturity was estimated to be 50 to 55 mm mantle length (ML) for males and 55 to 60 mm ML for females. Indirect evidence suggests that the final phases of the maturity process in females occur abruptly at some point after that size, and that recruit- ment of juveniles follows spawning and subsequent mortality or emigration of adults from the sampling area. Spawning is likely to take place in late summer and late winter INTRODUCTION Mexico Loligo pealei spawns throughout the year (Hixon 1980). Sepioteuthis sepioidea in the western Basic information on maturation and size at maturity tropical Atlantic and S. lessoniana in the western is fragmentary for many cephalopods, especially for Pacific also spawn year-round (Choe 1966, LaRoe those living in non-seasonal environments.
    [Show full text]
  • A FULL DESCRIPTION of LOLIGO SANPAULENSIS, Brakonieckl
    BULLETIN OF MARINE SCIENCE, 34(3): 435-448, 1984 A FULL DESCRIPTION OF LOLIGO SANPAULENSIS, BRAKONIECKl, 1984 AND A REDESCRIPTION OF LOLIGO GAHI D'ORBIGNY, 1835, TWO SPECIES OF SQUID (CEPHALOPODA; MYOPSIDA) FROM THE SOUTHWEST ATLANTIC Thomas F. Brakoniecki ABSTRACT The species of squid referred to as Loligo brasiliensis Blainville, 1823 by Castellanos and Cazzaniga (1979) is shown to be Loligo sanpaulensis (Brakoniecki, 1984). The name Loligo brasiliensis is shown to be a nomen dubium. Loligo gahi d'Orbigny, 1835 and L. sanpaulensis are redescribed and illustrated. Loligo patagonica Smith, 1881 is shown to be a synonym of L. gahi. Loligo ellipsura Hoyle, 1885 is shown to be a nomen dubium. The distribution and identification of Loligo sanpau/ensis and L. gahi are discussed. During the summer of 1982, I was asked to identify some squid obtained by Dr. F. J. Palacio from the coastal waters of Argentina, Uruguay and Brazil. After examining the collection and reviewing the literature, it was evident that the loliginid squid in this area were in need of taxonomic revision. Four nominal species of squid have been reported from these waters: Loligo brasiliensis Blainville, 1823, L. gahi d'Orbigny, 1835, L. patagonica Smith, 1881 and L. ellipsura Hoyle, 1885. These have been discussed in several papers (Cas- tellanos, 1967a; b; Castellanos and Menni, 1968; Filippova, 1969; Castellanos and Cazzaniga, 1977; 1979). In the last of these papers the authors concluded that only two species of loliginids occur in the area, Loligo brasiliensis and L. gahi. Loligo patagonica and L. ellipsura were considered to be junior synonyms of L.
    [Show full text]
  • Aspects of the Early Life History of Loligo Pealei (Cephalopoda:Myopsida)
    W&M ScholarWorks VIMS Articles Virginia Institute of Marine Science 1981 Aspects of the early life history of Loligo pealei (Cephalopoda:Myopsida) Michael Vecchione Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/vimsarticles Part of the Marine Biology Commons Recommended Citation Vecchione, Michael, Aspects of the early life history of Loligo pealei (Cephalopoda:Myopsida) (1981). Journal of Shellfish Research, 1(2), 171-180. https://scholarworks.wm.edu/vimsarticles/2173 This Article is brought to you for free and open access by the Virginia Institute of Marine Science at W&M ScholarWorks. It has been accepted for inclusion in VIMS Articles by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Journal of Shellfish Research, Vol. 1, No. 2, 171-180, 1981. ASPECTS OF THE EARLY LIFE HISTORY OF LOL/GO PEALE/ (CEPHALOPODA; MYOPS1DA) 1 MICHAEL VECCHI0NE 2 Virginia Institute of Marine Science and School of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062 ABSTRACT The long-finned squid Loligo pealei was the most common squid collected in 2 years of zooplankton samp­ ling over the Middle Atlantic Bight off New Jersey and Virginia. Planktonic specimens of L. pealei were found in that area during spring, summer, and fa ll ; there were no indications of multiple stocks. This species was captured in waters with a salinity range of 31.5 to 34.0 ppt, and was confined to coastal waters except when current conditions, such as the passage of a Gulf Stream eddy, resulted in strong, offshore surface transport.
    [Show full text]