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Warwick H H Sauer - One of the best experts on this subject based on the ideXlab platform.
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spatio temporal patterns in maturation of the chokka squid Loligo vulgaris reynaudii off the coast of south africa
Ices Journal of Marine Science, 2006Co-Authors: L J H Olyott, Warwick H H Sauer, Anthony J BoothAbstract:Knowledge of the temporal and spatial characteristics of chokka squid (Loligo vulgaris reynaudii) biology in South African waters is limited, so the possibility of there being a geographically fragmented stock was examined by investigating the distribution of maturity patterns for the species, covering all known spawning areas and using both historical and recent data. Gonadosomatic indices (GSI) varied between year-round consistency and apparent seasonal peaks in both summer and winter; there was no clear spatial pattern. Monthly percentage maturity provided further evidence for two peak reproductive periods each year, although mature squid were present throughout. Sex ratios demonstrated great variability between different areas and life history stages. Male-biased sex ratios were only apparent on the inshore spawning grounds and ranged between 1.118:1 and 4.267:1. Size at sexual maturity was also seasonal, squid maturing smaller in winter/spring than in summer/autumn. Also, squid in the east matured smaller than squid in the west. Although the results from the present study do not provide conclusive evidence of distinct geographic populations, squid likely spawn over a significantly larger area of the Agulhas Bank than previously estimated, and squid on the west coast of South Africa may return to spawn on the western portion of the Agulhas Bank. It remains likely, however, that the east and west coast populations are a single stock and that migration of juveniles to the west coast and their subsequent return as sub-adults is an integral but non-essential and variable part of the life history.
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multiple paternity and complex fertilisation dynamics in the squid Loligo vulgaris reynaudii
Marine Ecology Progress Series, 2004Co-Authors: Paul W Shaw, Warwick H H SauerAbstract:Predictions regarding multiple paternity and male mating competition in the squid Loligo vulgaris reynaudii D'Orbigny, based upon behavioural observations, were tested by DNA fingerprinting of offspring within wild caught egg strings along with putative female and male parents. Results confirm that the potential for multiple mating by females does translate into multiple paternity within broods, at least in some instances, with up to 4 or 5 males gaining fertilisations. Patterns of fertilisation success within egg strings demonstrated distinctly different levels of success by males, both within the brood as a whole but also along the length of a string. These preliminary results confirm an emerging picture of complex genetic mating systems in squid, and suggest the action of intricate patterns of sperm competition and the possibility of cryptic female choice in this species.
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temperature effects on the embryonic development and hatching success of the squid Loligo vulgaris reynaudii
Bulletin of Marine Science, 2002Co-Authors: Ané Oosthuizen, Michael J. Roberts, Warwick H H SauerAbstract:The squid Loligo vulgaris reynaudii spawns in two environmentally different areas, shallow (<60 m) inshore bays and in deeper (60-120 m) waters on the mid-continental shelf off the south east coast of South Africa. The temperature regimes between these two spawning environments are variable. The effects oftemperature on the embryonic development of L. v. reynaudii were investigated at both stable and fluctuating laboratory temperatures and natural fluctuating conditions. The relationship between embryonic development time and water temperature was defined by a polynomial regression function. Embryonic development time decreased with increasing temperature. An optimum temperature range for development was identified between 12°C and ∼17°C, at which development took 50.1 and ∼26.6 d, respectively. Outside the optimal temperature range (9°C and 21°C) abnormal embryonic development occurred. Fluctuating temperature experiments were based on inshore temperature data collected over 7 yrs. The early development stages were more sensitive to variable temperature regimes than later development stages. Embryonic development under laboratory and natural conditions was similar. Natural upwelling events in the inshore spawning areas had a negligible effect on the development success of eggs in these areas.
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tag recapture studies of the chokka squid Loligo vulgaris reynaudii d orbigny 1845 on inshore spawning grounds on the south east coast of south africa
Fisheries Research, 2000Co-Authors: Warwick H H Sauer, Marek R. Lipinski, C. J. AugustynAbstract:Abstract To study their migratory movements, Chokka squid ( Loligo vulgaris reynaudii ) were tagged on their inshore spawning grounds in early summer: 1748 in November 1992 and 4335 in November 1993. Squids were captured by hand jigging in depths of 24–35 m. Diving observations revealed that the behaviour pattern of recently tagged individuals was similar to that of untagged squid on the spawning grounds. Recaptures from commercial jigging vessels subsequent to tagging were 33 (1.89%) in 1992 and 387 (9.04%) in 1993. The longest tag-recapture duration was 32 days. Loligo. v. reynaudii moved to other spawning sites within the general spawning area, up to 207 km within 18 days. In 1993, mean speed was calculated as 3.0 km/day and mean distance travelled 42.8 km in a mean time of 14 days. Squids dispersed predominantly eastward from those tagged on the westward limit of their inshore spawning grounds. Those tagged towards the centre appeared to move randomly between spawning sites, possibly influenced by environmental conditions and food availability. Loligo v. reynaudii may be considered an uniseasonal-iteroparous species, maximising their reproductive potential by depositing eggs over an extended period in a number of spawning sites.
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confirmation of serial spawning in the chokka squid Loligo vulgaris reynaudii off the coast of south africa
Marine Biology, 1999Co-Authors: Y C Melo, Warwick H H SauerAbstract:Ovary maturation and spawning in the chokka squid Loligo vulgaris reynaudii were investigated by collecting squid from across their distributional range on the southeastern coast of South Africa between 1992 and 1993. Based on histological examination of the ovarian tissue and the separation of multiple modes in oocyte size-frequency distribution, ovary development was characterised by eight distinct stages. Our study confirms serial spawning in L. v. reynaudii.
Francisco Rocha - One of the best experts on this subject based on the ideXlab platform.
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Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters
Hydrobiologia, 2011Co-Authors: Jennifer M. Smith, Graham J. Pierce, Alain F. Zuur, Helen Martins, M. Clara Martins, Filipe Porteiro, Francisco RochaAbstract:The veined squid, Loligo forbesii , is found throughout the northeast Atlantic, including the waters off the Iberian Peninsula, and is a socio-economically important cephalopod species, sustaining several small-scale commercial and local artisanal fisheries. This study uses Iberian and Azorean trawl survey and fishery landings data from 1990 to 1992 and employs additive modelling to examine the relationships amongst somatic growth, season and gonad growth, in an attempt to determine the relative importance of intrinsic (e.g. nutritional state and body size) and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii . We compare the results with those from a comparative analysis of contemporaneous data on Loligo vulgaris from the Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. Reproductive organ weight in both sexes of L. forbesii from all ports shows seasonal patterns with a fall/winter peak in maturation, as is expected with the animals’ year-long life cycle. Two maturity peaks (spring and winter) were found for both Azores L. forbesii males and females, possibly evidence of two breeding cohorts, with males maturing approximately 1 month earlier than females in both seasons. For L. vulgaris , three annual peaks in reproductive weight were identified. With the exception of L. forbesii males from Scottish waters, in all study animals, the partial effect of mantle length and mantle weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status and reproductive weight is also generally positive. Geographic variation in the relationships, as seen between Scottish males and samples from the other study areas, is hypothesised to be largely attributable to local differences in environmental conditions (productivity, food availability, temperature, upwelling), although differences between L. forbesii from the Azores, Scotland and mainland Europe may also relate to previously documented genetic differences.
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embryonic life of the loliginid squid Loligo vulgaris comparison between statoliths of atlantic and mediterranean populations
Marine Ecology Progress Series, 2003Co-Authors: Roger Villanueva, Marek R. Lipinski, Alexander I Arkhipkin, C Peralesraya, Patrizia Jereb, E Lefkaditou, J Riba, Francisco RochaAbstract:Egg masses of the loliginid squid Loligo vulgaris Lamarck, 1798 are attached to hard sub- stratum or branched sessile organisms on the sea bottom. Embryonic development lasts from a few weeks to a few months, depending on the environmental water temperature. Because embryonic sta- tolith growth of L. vulgaris is very sensitive to temperature under laboratory conditions, we analyzed the possibilities of determining past events in the squid's early life from analysis of the embryonic area of sta- toliths of wild squid populations. The relationship between egg-incubation temperature and daily growth of embryonic statoliths under laboratory conditions was determined by tetracycline markings at 10 incubation temperatures ranging from 12 to 24.7°C. In addition, the mean width of embryonic increments in statolith collections of wild L. vulgaris from the Eastern Atlantic (Saharan Bank and NW Iberian Peninsula) and the Mediterranean Sea (Central and Eastern) was calculated. The temperature inferred from the embryonic increment widths of the statoliths of wild squid indicates that embryonic de- velopment of L. vulgaris in the regions sampled is likely to occur at temperatures ranging from 12 to 17°C. Mediterranean squid have wider embryonic increments than Atlantic squid, reflecting the slightly higher water temperatures in the Mediterranean Sea during the development of the egg masses. Eggs of L. vulgaris spawned off the NW Iberian Peninsula were estimated, on average, to remain at sea for 47 d, 1 wk longer than Mediterranean eggs (nearly 1 mo longer when comparing minimum and maxi- mum ranges). A longer incubation time for egg masses attached to the sea bottom increases mortality risks. Conversely, slow development at a lower temperature can improve yolk conversion, producing larger hatchlings, and increased hatching competence is expected from such squid. Therefore, a com- promise between longer-versus-shorter incubation time and related characteristics does exist.
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age and growth of two sympatric squid Loligo vulgaris and Loligo forbesi in galician waters north west spain
Journal of the Marine Biological Association of the United Kingdom, 1999Co-Authors: Francisco Rocha, Ángel GuerraAbstract:Age and growth of Loligo vulgaris and L. forbesi were studied by the examination of growth increments in 96 and 135 selected (white zone <10%) 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 different. 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. vulgaris was about one year whereas the life span of L. forbesi extended to 18 months.
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Signs of an extended and intermittent terminal spawning in the squids Loligo vulgaris Lamarck and Loligo forbesi Steenstrup (Cephalopoda: Loliginidae)
Journal of Experimental Marine Biology and Ecology, 1996Co-Authors: Francisco Rocha, Ángel GuerraAbstract: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.
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The diets of Loligo vulgaris and L. forbesi (Cephalopoda: Loliginidae) in northwestern Spanish Atlantic waters
Sarsia, 1994Co-Authors: Francisco Rocha, Bernardino G. Castro, María S. Gil, Ángel GuerraAbstract:Abstract The stomach contents of 723 Loligo vulgaris and 440 Loligo forbesi caught in the northwestern Spanish Atlantic waters have been examined. The diets of both species are described and compared. Loligo vulgaris shows 28 different types of prey belonging to four groups (Teleostei, Crustacea, Cephalopoda and Polychaeta) and Loligo forbesi 27 different types of prey belonging to three groups (Teleostei, Crustacea and Cephalopoda). Both species catch similar prey species but in different proportions. Cannibalism was observed in both species. Estimated prey sizes were smaller than squid sizes. No differences in feeding habits of males and females of both species were observed, but females seem to increase food intake during maturation. No significant changes were found in the diet of Loligo vulgaris within the size (DML) range studied (65–465 mm). Importance of cephalopods increased and importance of fish decreased in the diet of Loligo forbesi with growth (65–685 mm). Diet and food intake varied with se...
Ángel Guerra - One of the best experts on this subject based on the ideXlab platform.
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Predation behaviour of the European squid Loligo vulgaris
Journal of Ethology, 2020Co-Authors: Alejandro Carreño Castilla, Ángel Guerra, Jorge Hernández-urcera, Adam Gouraguine, Miguel Cabanellas-reboredoAbstract:To improve limited knowledge of the predation behaviour of the loliginid species, this study is the first to examine the hunting and feeding behaviour of Loligo vulgaris . Hunting and feeding strategy, as well as body patterning of the squid were described in laboratory experiments during which, two prey types, characterised by different size and mobility (prawn and fish), were offered to the squid. According to the type and distance of the prey, three hunting strategies were observed: to seize larger, farthest and high-mobility prey (fish), squid used tentacles as the main predatory tool (tentacular lunge attack); squid conducted an arm-opening attack to capture smaller and less mobile prey (prawn), but a mixed-strategy using both arms and tentacles was executed when the prawn was further away. Once captured, prawns were consumed alive, while the squid administered a lethal bite to the fish prior to consumption. Fish were always eaten in head-caudal fin direction. Size-feeding strategy differences were also observed. Largest squid ate faster and consumed the entire prey, while smaller squid rejected certain parts of the fish prey. Better prey-handling skills and larger feeding apparatus (e.g., beak) of larger squid (older/experienced individuals) are the likely causes. Finally, a prey-specific body pattern was performed depending on the prey exigency levels.
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application of the gomez munoz model to estimate catch and effort in the artisanal fishery for the squid Loligo vulgaris mollusca cephalopoda in the ria de vigo nw spain
Scientia Marina, 2019Co-Authors: Natalia Comesana, Ángel GuerraAbstract:The Gomez-Munoz model was developed to aid the management of small-scale or artisanal fisheries and is based on interview data from fishermen and other personnel directly related to the fishery. The non-targeted and targeted Loligo vulgaris fishery in the Ria de Vigo and the Aldan Cove is explored. Eighty-one interviews were carried out. This survey yielded 38 valid interviews, which were used to estimate the parameters of the model for the period 2011-2015. Comparison between official landings and catches estimated by this model showed discrepancies varying between 41.8% and 98.4%, depending on the fish markets considered. An 82.2% decrease of the squid catches over the period 2011-2015 was recorded. The reasons for that drop as well as the sensitivity and accuracy of the model are discussed.
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new insights on the external features of egg capsules and embryo development in the squid Loligo vulgaris
Journal of Natural History, 2016Co-Authors: Paloma Feyjoo, Angel F Gonzalez, Miguel Cabanellasreboredo, Matias Calvomanazza, Beatriz Moralesnin, Jorge Hernandezurcera, Manuel E Garci, Ángel GuerraAbstract:AbstractThe embryonic development of the squid Loligo vulgaris was observed from 183 egg masses collected from special devices deployed throughout Cabrera National Park (Baleares Islands, western Mediterranean Sea). Sequence alignment analysis of the cytochrome oxidase I gene revealed that all embryos belonged to L. vulgaris. In total, 549 egg capsules were examined. Viable egg capsules (n = 420) were classified into one of five maturation stages according to the primary external features. The length of the viable egg capsules varied between 40 and 170 mm, and increased with embryonic development. The non-viable capsules (n = 129) were categorized into four groups: I (Ginger root), non-viable II and III, and empty egg capsule (IV). The percentage of non-viable capsules (i.e. grades I, II and III) was 92.25%. Empty capsules accounted for 7.75% of the total non-viable egg capsules. Embryonic development was classified into a second scale of eight stages. Egg capsule stage and embryonic stage were significan...
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age growth and mortality of Loligo vulgaris wild paralarvae implications for understanding of the life cycle and longevity
Ices Journal of Marine Science, 2010Co-Authors: Angel F Gonzalez, Graham J. Pierce, Jaime Otero, Ángel GuerraAbstract:Gonzalez, A. F., Otero, J., Pierce, G. J., and Guerra, A. 2010. Age, growth, and mortality of Loligo vulgaris wild paralarvae: implications for understanding of the life cycle and longevity. - ICES Journal of Marine Science, 67: 1119-1127.Age, growth, and mortality were estimated for the first time in wild paralarvae of the common squid, Loligo vulgaris, by examining growth increments in the statoliths of 273 animals collected off the Ria de Vigo (NW Spain, NE Atlantic). Hatching was all year round for the period 2003-2005, with a peak during late spring and a secondary peak during early autumn. Paralarvae varied from 1260 to 7580 μm, and their abundance decreased abruptly as they grew. Statolith increments were clearly visible without grinding in almost all material, allowing reliable estimation of age. Paralarvae are planktonic for at least 3 months. Growth in dorsal mantle length (DML) during that period fitted an exponential equation. The instantaneous relative growth rates were 2.11, 2.15, and 1.82% DML d −1 for 2003, 2004, and 2005, respectively, and there were no significant differences in size-at-age between the 3 years. Taking into account the growth rates estimated for the whole cycle of L. vulgaris, we suggest that the lifespan may previously have been underestimated by 3 months, because the proximity of the rings deposited during paralarval and early juvenile stages would prevent accuracy in enumerating the number of growth increments in later stages. The estimated instantaneous rate of total mortality during the first 90 d of a paralarva life was 9.6, 5.3, and 4.8% d −1 for 2003, 2004, and 2005, respectively. Eye diameter was a reliable and rapid way of estimating DML and age.
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age and growth of two sympatric squid Loligo vulgaris and Loligo forbesi in galician waters north west spain
Journal of the Marine Biological Association of the United Kingdom, 1999Co-Authors: Francisco Rocha, Ángel GuerraAbstract:Age and growth of Loligo vulgaris and L. forbesi were studied by the examination of growth increments in 96 and 135 selected (white zone <10%) 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 different. 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. vulgaris was about one year whereas the life span of L. forbesi extended to 18 months.
Marek R. Lipinski - One of the best experts on this subject based on the ideXlab platform.
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embryonic life of the loliginid squid Loligo vulgaris comparison between statoliths of atlantic and mediterranean populations
Marine Ecology Progress Series, 2003Co-Authors: Roger Villanueva, Marek R. Lipinski, Alexander I Arkhipkin, C Peralesraya, Patrizia Jereb, E Lefkaditou, J Riba, Francisco RochaAbstract:Egg masses of the loliginid squid Loligo vulgaris Lamarck, 1798 are attached to hard sub- stratum or branched sessile organisms on the sea bottom. Embryonic development lasts from a few weeks to a few months, depending on the environmental water temperature. Because embryonic sta- tolith growth of L. vulgaris is very sensitive to temperature under laboratory conditions, we analyzed the possibilities of determining past events in the squid's early life from analysis of the embryonic area of sta- toliths of wild squid populations. The relationship between egg-incubation temperature and daily growth of embryonic statoliths under laboratory conditions was determined by tetracycline markings at 10 incubation temperatures ranging from 12 to 24.7°C. In addition, the mean width of embryonic increments in statolith collections of wild L. vulgaris from the Eastern Atlantic (Saharan Bank and NW Iberian Peninsula) and the Mediterranean Sea (Central and Eastern) was calculated. The temperature inferred from the embryonic increment widths of the statoliths of wild squid indicates that embryonic de- velopment of L. vulgaris in the regions sampled is likely to occur at temperatures ranging from 12 to 17°C. Mediterranean squid have wider embryonic increments than Atlantic squid, reflecting the slightly higher water temperatures in the Mediterranean Sea during the development of the egg masses. Eggs of L. vulgaris spawned off the NW Iberian Peninsula were estimated, on average, to remain at sea for 47 d, 1 wk longer than Mediterranean eggs (nearly 1 mo longer when comparing minimum and maxi- mum ranges). A longer incubation time for egg masses attached to the sea bottom increases mortality risks. Conversely, slow development at a lower temperature can improve yolk conversion, producing larger hatchlings, and increased hatching competence is expected from such squid. Therefore, a com- promise between longer-versus-shorter incubation time and related characteristics does exist.
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laboratory validation of periodicity of incrementation in statoliths of the south african chokka squid Loligo vulgaris reynaudii d orbigny 1845 a reevaluation
Journal of Experimental Marine Biology and Ecology, 2002Co-Authors: M D Durholtz, Marek R. Lipinski, J G FieldAbstract:Abstract The periodicity of increment formation in statoliths of the South African chokka squid Loligo vulgaris reynaudii (d'Orbigny, 1845) is tested using the results of laboratory statolith marking experiments. Statoliths of live squid were marked by oxytetracycline injection, and the squid released into tanks in the laboratory. Two of the squid survived for a sufficient period to permit the application of a second mark. The statoliths were extracted from squid recaptured after a known period and prepared for examination by light and UV fluorescence microscopy. Statoliths from 102 squid were obtained from the experiment, of which 75 (36 males and 39 females ranging from 1 to 29 days postmarking) were successfully prepared for examination. Three replicate counts of the number of increments deposited after marking were recorded from each statolith. The quality of each statolith preparation was quantified during each replicate reading, and these values were used to filter the data to exclude the results from average and below average preparations. The statoliths of 16 squid fulfilled the filtering criteria (11 males and 5 females, 1–29 days and 1–13 days postmarking, respectively). Replicate increment counts were felt to be adequately precise to use the mean increment count as an estimate of the number of increments deposited after marking. The daily increment hypothesis was tested using simple linear regression and statistical power analyses. The data obtained from good statolith preparations strongly support the daily increment hypothesis, although this conclusion should be treated with caution with regard to female squid. Estimates of the statistical power of the conclusions were relatively low, primarily as a result of small sample size. Increment deposition rates in male chokka squid in the laboratory were comparable to those of male squid in a previously reported field study, suggesting that the results of laboratory experiments can be extended to squid in the wild. A possible difference in the readability of statoliths between the sexes is apparent and requires further investigation.
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tag recapture studies of the chokka squid Loligo vulgaris reynaudii d orbigny 1845 on inshore spawning grounds on the south east coast of south africa
Fisheries Research, 2000Co-Authors: Warwick H H Sauer, Marek R. Lipinski, C. J. AugustynAbstract:Abstract To study their migratory movements, Chokka squid ( Loligo vulgaris reynaudii ) were tagged on their inshore spawning grounds in early summer: 1748 in November 1992 and 4335 in November 1993. Squids were captured by hand jigging in depths of 24–35 m. Diving observations revealed that the behaviour pattern of recently tagged individuals was similar to that of untagged squid on the spawning grounds. Recaptures from commercial jigging vessels subsequent to tagging were 33 (1.89%) in 1992 and 387 (9.04%) in 1993. The longest tag-recapture duration was 32 days. Loligo. v. reynaudii moved to other spawning sites within the general spawning area, up to 207 km within 18 days. In 1993, mean speed was calculated as 3.0 km/day and mean distance travelled 42.8 km in a mean time of 14 days. Squids dispersed predominantly eastward from those tagged on the westward limit of their inshore spawning grounds. Those tagged towards the centre appeared to move randomly between spawning sites, possibly influenced by environmental conditions and food availability. Loligo v. reynaudii may be considered an uniseasonal-iteroparous species, maximising their reproductive potential by depositing eggs over an extended period in a number of spawning sites.
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Daily net emigration from a spawning concentration of chokka squid (Loligo vulgaris reynaudii d'Orbigny, 1845) in Kromme Bay, South Africa
Ices Journal of Marine Science, 1998Co-Authors: Marek R. Lipinski, I. Hampton, Warwick H H Sauer, C. J. AugustynAbstract:The net emigration from a spawning concentration of the loliginid squid, Loligo vulgaris reynaudii d’Orbigny, 1845, was investigated quantitatively using a combination of tagging and hydroacoustic techniques, midwater trawling, purse seining and SCUBA diving. Aquarium experiments were used to supply additional information on tag loss and mortality from tagging. The number of squid in a concentration containing T tagged individuals was assessed hydroacoustically and then c squid were caught by means of a midwater trawl or purse seine. It was assumed that the tn tagged squids in these catches were the result of natural mortality, tagging mortality and net stability of the concentration (the result of emigration and immigration) n days after tagging. The average net emigration was then calculated to be 0.2 per day for 7.5 days of observations. This result is a first attempt to solve the so-called ‘‘Hilborn’s problem’’, i.e. the problem of how to measure the aggregation dynamics of nektonic organisms in the sea (instead of modelling). ? 1998 International Council for the Exploration of the Sea
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field validation of age readings from the statoliths of chokka squid Loligo vulgaris reynaudii d orbigny 1845 and an assessment of associated errors
Ices Journal of Marine Science, 1998Co-Authors: Marek R. Lipinski, M D Durholtz, Les G UnderhillAbstract:Lipinski, M. R., Durholtz, M. D., and Underhill, L. G. Field validation of age readings from the statoliths of chokka squid (Loligo vulgaris reynaudii d’Orbigny, 1845) and an assessment of associated errors. ‐ ICES Journal of Marine Science, 55: 240‐257. This paper describes the first successful field tag-recapture experiment, aimed at validating daily increments in the statoliths of chokka squid (Loligo vulgaris reynaudii). Seven hundred and forty-two squid were tagged and injected with oxytetracycline (OTC) and 63 were subsequently recovered after 4‐20 days spent free in the sea. Forty-seven statoliths were successfully prepared for increment reading, eight of which satisfied stringent requirements for validation: good visibility of increments, sharp definition of the OTC band and a clear, undamaged margin. These eight statoliths yielded results indicating that the increments in chokka males in the size range 290‐370 mm mantle length (ML) were deposited daily and that the same was true for a 173 mm ML female. The results of an analysis of the errors involved in the increment recognition stage (counting) do show, however, that proper statolith preparation, increment identification and subsequent reading are crucial for obtaining accurate age estimates. The error in counting increments in a poorly prepared statolith may be three times higher than the error for a well prepared statolith in the technique used, which is felt to be one of the best presently available. This technique relies on the grinding of both sides of the statolith in the frontal plane (contrary to the most frequently used transverse sections). Precise position of the grinding plane is determined and maintained during the procedure. ? 1998 International Council for the Exploration of the Sea
Graham J. Pierce - One of the best experts on this subject based on the ideXlab platform.
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the effect of temperature on growth of early life stages of the common squid Loligo vulgaris
Journal of the Marine Biological Association of the United Kingdom, 2012Co-Authors: Ana Moreno, Graham J. Pierce, João Pereira, Manuela Azevedo, A M P SantosAbstract:The squid Loligo vulgaris has an extended spawning season within the upwelling system off north-west Portugal, and its paralarvae may thus develop under a wide range of environmental conditions. Both temperature and salinity are expected to affect the metabolism of young squid and we tested their effects on growth during the embryonic and post-hatching phase, based on measurements of growth increments in statoliths of juveniles and adults, using generalized additive models. There was no evidence that statolith increments representing early growth become unreadable in adult statoliths. Variability in the statolith size at hatching was weakly but significantly related to the variables in the model. On the other hand, the effects on statolith growth of both sea surface temperature and of sea bottom temperature were significant during early post-hatching life. Thicker increments are deposited in the statoliths of squid living under higher temperatures, which results in summer hatchers having larger statoliths at the age of 90 days. Inspection of the statolith accretion pattern, using a piecewise linear regression method, revealed an ontogenetic shift in increment width, which may be an indication of the age of transition from paralarva to juvenile. On this basis, it is suggested that the planktonic stage lasts 60 or 90 days, depending on whether the paralarvae lived at higher (>15°C) or lower (<15°C) sea surface temperatures. The life strategy under warmer conditions potentially favours survival by reducing the duration of the vulnerable planktonic phase.
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Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters
Hydrobiologia, 2011Co-Authors: Jennifer M. Smith, Graham J. Pierce, Alain F. Zuur, Helen Martins, M. Clara Martins, Filipe Porteiro, Francisco RochaAbstract:The veined squid, Loligo forbesii , is found throughout the northeast Atlantic, including the waters off the Iberian Peninsula, and is a socio-economically important cephalopod species, sustaining several small-scale commercial and local artisanal fisheries. This study uses Iberian and Azorean trawl survey and fishery landings data from 1990 to 1992 and employs additive modelling to examine the relationships amongst somatic growth, season and gonad growth, in an attempt to determine the relative importance of intrinsic (e.g. nutritional state and body size) and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii . We compare the results with those from a comparative analysis of contemporaneous data on Loligo vulgaris from the Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. Reproductive organ weight in both sexes of L. forbesii from all ports shows seasonal patterns with a fall/winter peak in maturation, as is expected with the animals’ year-long life cycle. Two maturity peaks (spring and winter) were found for both Azores L. forbesii males and females, possibly evidence of two breeding cohorts, with males maturing approximately 1 month earlier than females in both seasons. For L. vulgaris , three annual peaks in reproductive weight were identified. With the exception of L. forbesii males from Scottish waters, in all study animals, the partial effect of mantle length and mantle weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status and reproductive weight is also generally positive. Geographic variation in the relationships, as seen between Scottish males and samples from the other study areas, is hypothesised to be largely attributable to local differences in environmental conditions (productivity, food availability, temperature, upwelling), although differences between L. forbesii from the Azores, Scotland and mainland Europe may also relate to previously documented genetic differences.
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age growth and mortality of Loligo vulgaris wild paralarvae implications for understanding of the life cycle and longevity
Ices Journal of Marine Science, 2010Co-Authors: Angel F Gonzalez, Graham J. Pierce, Jaime Otero, Ángel GuerraAbstract:Gonzalez, A. F., Otero, J., Pierce, G. J., and Guerra, A. 2010. Age, growth, and mortality of Loligo vulgaris wild paralarvae: implications for understanding of the life cycle and longevity. - ICES Journal of Marine Science, 67: 1119-1127.Age, growth, and mortality were estimated for the first time in wild paralarvae of the common squid, Loligo vulgaris, by examining growth increments in the statoliths of 273 animals collected off the Ria de Vigo (NW Spain, NE Atlantic). Hatching was all year round for the period 2003-2005, with a peak during late spring and a secondary peak during early autumn. Paralarvae varied from 1260 to 7580 μm, and their abundance decreased abruptly as they grew. Statolith increments were clearly visible without grinding in almost all material, allowing reliable estimation of age. Paralarvae are planktonic for at least 3 months. Growth in dorsal mantle length (DML) during that period fitted an exponential equation. The instantaneous relative growth rates were 2.11, 2.15, and 1.82% DML d −1 for 2003, 2004, and 2005, respectively, and there were no significant differences in size-at-age between the 3 years. Taking into account the growth rates estimated for the whole cycle of L. vulgaris, we suggest that the lifespan may previously have been underestimated by 3 months, because the proximity of the rings deposited during paralarval and early juvenile stages would prevent accuracy in enumerating the number of growth increments in later stages. The estimated instantaneous rate of total mortality during the first 90 d of a paralarva life was 9.6, 5.3, and 4.8% d −1 for 2003, 2004, and 2005, respectively. Eye diameter was a reliable and rapid way of estimating DML and age.
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growth strategies in the squid Loligo vulgaris from portuguese waters
Marine Biology Research, 2007Co-Authors: Ana Moreno, Manuela Azevedo, J S Pereira, Graham J. PierceAbstract:Abstract The growth of the European squid Loligo vulgaris in northwest Portuguese waters is described and the influences of gender and hatching season analysed, based on statolith readings from individuals of a wide range of sizes. Male and female growth follows different models, males attaining a higher length-at-age than females. Males display increasing growth rates irrespective of the hatching season, but the length-at-age is higher in animals hatched during the warm season. Females may exhibit asymptotic growth or not, depending upon the environmental conditions to which they are exposed through their life cycle. Although growth rates after hatching are lower in females hatched during the cold season, favourable feeding and temperature conditions during the following spring and summer months contribute not only to increase growth rates but also to delay sexual maturation. The higher length-at-age of squid hatching in the warm season, observed in both genders, provides evidence that the temperature cl...
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on reproduction and age of the squid Loligo vulgaris from the saharan bank north west african coast
Journal of the Marine Biological Association of the United Kingdom, 1999Co-Authors: C P Raya, Eduardo Balguerias, M M Fernandeznunez, Graham J. PierceAbstract:Loligo vulgaris (Cephalopoda: Loliginidae) is a commercially important species in the cephalopod trawl ¢shery in the Saharan Bank (21^268N). This study on squid in central-east Atlantic waters aims to examine some important aspects of its reproductive biology. In the period from May 1993 to April 1994 monthly samples of L. vulgaris were collected from this commercial trawl ¢shery. The maturation pattern for males and females was described from the proportion of immature, maturing and mature animals in the samples and using a maturation index. A range of reproductive indices derived from the morphometrics of the somatic and reproductive systems were also estimated to provide comparative information. The proportion and an abundance index of mature and immature animals in commercial landings in the period 1983^1994 were calculated to provide comparative results of maturity and recruitment respectively. Peaks of mature animals were mainly seen between November and January. The summer months exhibited the maximum recruit abundance. Age determinations were also undertaken in order to obtain the hatching peaks and to complete the proposed life cycle of L. vulgaris on the Saharan Bank. A main hatching peak was observed in spring, particularly in May.The age^size relationship suggests diierences related to sex and possibly to hatching season. The wide range of size at maturity observed in male L. vulgaris is analysed and discussed. Males showed a seasonal pattern in size at maturity. The dorsal mantle length^body weight relationship and the sex ratio were determined. The sex ratio exhibits a seasonal pattern in relation to body size. Results are compared with information on this species from European waters.
