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Francisco Rocha - One of the best experts on this subject based on the ideXlab platform.
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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...
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The life history of Loligo vulgaris and Loligo forbesi (Cephalopoda: Loliginidae) in Galician waters (NW Spain)
Fisheries Research, 1994Co-Authors: Ángel Guerra, Francisco RochaAbstract:Abstract The population biology of Loligo vulgaris and Loligo forbesi in Galician waters is described based on monthly samples from the fishery obtained during the period February 1991–June 1992. Maturity was assessed using a maturity scale and indices. The estimated number of oocytes in mature females varied from 782 to 21 885 in L. vulgaris and from 1317 to 14 956 in L. forbesi , and showed a slight positive correlation with the length of the mantle ( ML ) for both species. Oocytes in the ovaries fall into three discrete size classes, which suggests that L. vulgaris and L. forbesi are intermittent or multiple spawning species. In L. vulgaris males mature at two different modal sizes, hence perhaps at two different ages, while in L. forbesi this occurs in both males and females. Males mature earlier in the season than females in both species. The maximum number of spermatophores found was 1010 and 1000 in two L. vulgaris males with 119 mm and 400 mm ML respectively, and 1035 in a L. forbesi male with 150 mm ML . In both species, spermatophore length increases with ML . Loligo forbesi males maturing at a larger size produce fewer but larger spermatophores than those maturing at a small size. Loligo vulgaris spawn throughout the year, but the period of more intensive spawning extends from December to April. The breeding season of L. forbesi extends from December to May, the more intensive spawning extending from December to February. Sex ratios were variable for both species. Age and growth for both species and sexes were estimated by examining growth increments in the statoliths. Like-sized individuals had different ages in both species. The life span of L. vulgaris was estimated at about 1 year while L. forbesi seems to reach an age of 15–16 months. A list of prey species found in gastric contents of both species is given. The diet of L. vulgaris comprises fish (86.8%), cephalopods (6.0%), crustaceans (3.0%) and polychaetes (1.8%), and the diet of L. forbesi includes fish (75.6%), crustaceans (18.5%) and cephalopods (4.4%).
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The Spanish fishery for Loligo: recent trends
Fisheries Research, 1994Co-Authors: Ángel Guerra, Pilar Sánchez, Francisco RochaAbstract:Abstract The Spanish fishery for the loliginid squids Loligo vulgaris and Loligo forbesi is described, with particular emphasis on the period 1983–1991. During this period the landings of squid in Spain stayed at a relatively constant level of around 2200 t. The value of the Spanish squid landings increased throughout the 1980s and amounted to £9.7 million in 1991. The two species of squid are not treated separately in the official statistics, and therefore the percentage corresponding to each is unknown; nevertheless, in the maritime regions of the Mediterranean, L. vulgaris is practically the only species landed, while in Atlantic regions, both are landed, although L. vulgaris is more abundant than L. forbesi . Particular attention is paid to the analysis and description of fisheries and squid landings in Galicia (northwest Spain) and Catalonia (northeast Spain), during the period 1980–1991. In both regions, part of the landings correspond to trawling and purse-seine fisheries targeting finfish, where squid is caught as a by-catch. There are also important seasonal artisanal fisheries where the target species is squid. Landings have shown a marked seasonality, being more plentiful in summer and autumn. This resource does not show signs of overfishing. The present methods of fishing management are discussed, and proposals are put forward to modify some of these in order to avoid catching immature individuals of less than 200 mm mantle length.
Ángel Guerra - One of the best experts on this subject based on the ideXlab platform.
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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...
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The life history of Loligo vulgaris and Loligo forbesi (Cephalopoda: Loliginidae) in Galician waters (NW Spain)
Fisheries Research, 1994Co-Authors: Ángel Guerra, Francisco RochaAbstract:Abstract The population biology of Loligo vulgaris and Loligo forbesi in Galician waters is described based on monthly samples from the fishery obtained during the period February 1991–June 1992. Maturity was assessed using a maturity scale and indices. The estimated number of oocytes in mature females varied from 782 to 21 885 in L. vulgaris and from 1317 to 14 956 in L. forbesi , and showed a slight positive correlation with the length of the mantle ( ML ) for both species. Oocytes in the ovaries fall into three discrete size classes, which suggests that L. vulgaris and L. forbesi are intermittent or multiple spawning species. In L. vulgaris males mature at two different modal sizes, hence perhaps at two different ages, while in L. forbesi this occurs in both males and females. Males mature earlier in the season than females in both species. The maximum number of spermatophores found was 1010 and 1000 in two L. vulgaris males with 119 mm and 400 mm ML respectively, and 1035 in a L. forbesi male with 150 mm ML . In both species, spermatophore length increases with ML . Loligo forbesi males maturing at a larger size produce fewer but larger spermatophores than those maturing at a small size. Loligo vulgaris spawn throughout the year, but the period of more intensive spawning extends from December to April. The breeding season of L. forbesi extends from December to May, the more intensive spawning extending from December to February. Sex ratios were variable for both species. Age and growth for both species and sexes were estimated by examining growth increments in the statoliths. Like-sized individuals had different ages in both species. The life span of L. vulgaris was estimated at about 1 year while L. forbesi seems to reach an age of 15–16 months. A list of prey species found in gastric contents of both species is given. The diet of L. vulgaris comprises fish (86.8%), cephalopods (6.0%), crustaceans (3.0%) and polychaetes (1.8%), and the diet of L. forbesi includes fish (75.6%), crustaceans (18.5%) and cephalopods (4.4%).
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The Spanish fishery for Loligo: recent trends
Fisheries Research, 1994Co-Authors: Ángel Guerra, Pilar Sánchez, Francisco RochaAbstract:Abstract The Spanish fishery for the loliginid squids Loligo vulgaris and Loligo forbesi is described, with particular emphasis on the period 1983–1991. During this period the landings of squid in Spain stayed at a relatively constant level of around 2200 t. The value of the Spanish squid landings increased throughout the 1980s and amounted to £9.7 million in 1991. The two species of squid are not treated separately in the official statistics, and therefore the percentage corresponding to each is unknown; nevertheless, in the maritime regions of the Mediterranean, L. vulgaris is practically the only species landed, while in Atlantic regions, both are landed, although L. vulgaris is more abundant than L. forbesi . Particular attention is paid to the analysis and description of fisheries and squid landings in Galicia (northwest Spain) and Catalonia (northeast Spain), during the period 1980–1991. In both regions, part of the landings correspond to trawling and purse-seine fisheries targeting finfish, where squid is caught as a by-catch. There are also important seasonal artisanal fisheries where the target species is squid. Landings have shown a marked seasonality, being more plentiful in summer and autumn. This resource does not show signs of overfishing. The present methods of fishing management are discussed, and proposals are put forward to modify some of these in order to avoid catching immature individuals of less than 200 mm mantle length.
Graham J. Pierce - One of the best experts on this subject based on the ideXlab platform.
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The apparent disappearance of Loligo forbesi from the south of its range in the 1990s: Trends in Loligo spp. abundance in the northeast Atlantic and possible environmental influences
Fisheries Research, 2006Co-Authors: Chih-shin Chen, Graham J. Pierce, João Pereira, Jianjun Wang, Jean-paul Robin, Jean-charles Poulard, Alain F. Zuur, Peter Robin Boyle, Nick Bailey, Doug BeareAbstract:Since the early 1990s, Loligo forbesi has apparently disappeared from much of the southern part of its former range, with catches off the Iberian Peninsula, for example, declining dramatically during the 1990s. The present paper assembles data from fishery and research cruise databases to examine the evidence for a shift in distribution, examine the relationship between abundance of this species and that of the partially sympatric Loligo vulgaris, and identify possible environmental correlates. Time-series of abundance of L. forbesi and L. vulgaris were assembled using fishery and survey data from Scotland, France, and Portugal. Based on availability of data and timing of the main fishery, data for autumn (October–December) were selected. Nine squid series and two explanatory variables (October sea surface temperature and the winter NAO index) were analysed using dynamic factor analysis (DFA). The optimal DFA model contained two common trends and both of the explanatory variables. The first common trend shows an increase from 1987 to 1999, and a slight decrease after 2000 onwards, and is positively related to L. forbesi abundance in the north of its range (Scotland), while negatively related to squid abundance (both species) in the south of their ranges (France and Portugal). The second trend identifies an increase from 1990 to 1995, followed by a decrease until 2002, and is positively related to the squid (L. forbesi and L. vulgaris) abundance series from French surveys and fisheries. The SST series was significantly related to three squid abundance series: positively with abundance of small L. forbesi in French surveys and negatively with the abundance of small L. forbesi from Scottish surveys and abundance of L. vulgaris in Portuguese surveys. The winter NAO series was significantly related to the abundance of small L. forbesi from Scottish surveys. The increase in SST after 1993 and subsequent high level may thus be associated with the decrease of Loligo abundance in the south area (France and Portugal) and the increase in Loligo abundance in the north area (Scotland).
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Temporal and spatial patterns in the distribution of squid Loligo spp. in United Kingdom waters
South African Journal of Marine Science, 1998Co-Authors: Claire M. Waluda, Graham J. PierceAbstract:A Geographic Information System (GIS) was used to test hypotheses regarding the spatial distribution of the squid Loligo forbesi and Loligo vulgaris vulgaris in the northern North-East Atlantic during the years 1989-1994. Loligo spp. were present throughout coastal waters of the United Kingdom, but distribution was patchy and highly variable over space and time. The relationship between squid distribution and sea temperature and salinity in the North Sea was examined by overlaying maps of squid abundance (landings per unit effort lpue) and oceanographic variables, and using correlation and multiple regression analysis. Bottom temperature was most frequently correlated with lpue, with correlations between squid and oceanographic parameters occurring most often in January and February of a given year. Monthly changes in distribution patterns are consistent with squid undertaking seasonal migrations around the coast of the U.K. It is at present unknown whether temperature and salinity influence squid distrib...
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Size selectivity in the diet of Loligo forbesi (Cephalopoda : Loliginidae)
Journal of the Marine Biological Association of the United Kingdom, 1996Co-Authors: Martin A. Collins, Graham J. PierceAbstract:The size of fish and squid prey of Loligo forbesi was investigated using otoliths, beaks and statoliths collected from stomach contents analysis of samples obtained from Scottish and Irish waters between 1990 and 1993. Loligo forbesi was found to consume a large range of prey sizes, but prey size was always less than the predator size. Season was shown to significantly influence the predator size-prey size relationship for sprat and sandeel prey, but this itself could be influenced by seasonal changes in the size of prey. Fish prey size increased with increased predator size up to a mantle length (ML) of 200 mm. Loligo forbesi of mantle length >200 mm consumed a range of prey sizes, with no clear increase in the size of prey. For most prey taxa the relationship between prey size and squid size was similar, the exceptions being dragonets and silvery pout. Cannibalism by L. forbesi was mostly limited to larger L. forbesi (>150 mm ML) feeding on smaller (20–50 mm ML) conspecifics.
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Diets of squid Loligo forbesi and Loligo vulgaris in the northeast Atlantic
Fisheries Research, 1994Co-Authors: Graham J. Pierce, Peter Boyle, Lee C. Hastie, M. Begofia SantosAbstract:Abstract Diets of the loliginid squid Loligo forbesi and Loligo vulgaris were investigated by stomach contents sampling during 1990–1993. Monthly samples of Loligo forbesi were collected at Aberdeen and additional samples were obtained from the Irish Sea, Faroe, the English Channel, Vigo, Lisbon and the Azores. Samples of Loligo vulgaris were obtained from Vigo, Barcelona, Lisbon and Faro. Loligo forbesi feeds primarily on fishes, crustaceans and cephalopods. In Scottish waters, Gadidae (mainly Merlangius merlangus and Trisopterus sp.), Ammodytidae and Clupeidae were the most frequently identified prey. The relative importance of fish was slightly higher, and that of crustaceans lower, in the diet of larger squid. Gadidae and Clupeidae were more prominent in the winter diet, with sandeels being taken more frequently in the summer. The same prey taxa were important in the diet of Loligo forbesi across all areas. Fishes occurred in more than 80% of non-empty stomachs except for the Lisbon sample, in which crustaceans were the most frequently identified prey taxon. The species composition of the diet varied between areas. Thus, scad Trachurus picturatus was the most important prey in the Azores. The broad composition of the diet in Loligo vulgaris was similar, although crustaceans were apparently less important, but there were differences in species eaten between areas, and between the two Loligo species. Samples of the ommastrephid squid Todaropsis eblanae taken at Aberdeen indicated that this species was also primarily piscivorous, taking Gadidae and Clupeidae.
João Pereira - One of the best experts on this subject based on the ideXlab platform.
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The apparent disappearance of Loligo forbesi from the south of its range in the 1990s: Trends in Loligo spp. abundance in the northeast Atlantic and possible environmental influences
Fisheries Research, 2006Co-Authors: Chih-shin Chen, Graham J. Pierce, João Pereira, Jianjun Wang, Jean-paul Robin, Jean-charles Poulard, Alain F. Zuur, Peter Robin Boyle, Nick Bailey, Doug BeareAbstract:Since the early 1990s, Loligo forbesi has apparently disappeared from much of the southern part of its former range, with catches off the Iberian Peninsula, for example, declining dramatically during the 1990s. The present paper assembles data from fishery and research cruise databases to examine the evidence for a shift in distribution, examine the relationship between abundance of this species and that of the partially sympatric Loligo vulgaris, and identify possible environmental correlates. Time-series of abundance of L. forbesi and L. vulgaris were assembled using fishery and survey data from Scotland, France, and Portugal. Based on availability of data and timing of the main fishery, data for autumn (October–December) were selected. Nine squid series and two explanatory variables (October sea surface temperature and the winter NAO index) were analysed using dynamic factor analysis (DFA). The optimal DFA model contained two common trends and both of the explanatory variables. The first common trend shows an increase from 1987 to 1999, and a slight decrease after 2000 onwards, and is positively related to L. forbesi abundance in the north of its range (Scotland), while negatively related to squid abundance (both species) in the south of their ranges (France and Portugal). The second trend identifies an increase from 1990 to 1995, followed by a decrease until 2002, and is positively related to the squid (L. forbesi and L. vulgaris) abundance series from French surveys and fisheries. The SST series was significantly related to three squid abundance series: positively with abundance of small L. forbesi in French surveys and negatively with the abundance of small L. forbesi from Scottish surveys and abundance of L. vulgaris in Portuguese surveys. The winter NAO series was significantly related to the abundance of small L. forbesi from Scottish surveys. The increase in SST after 1993 and subsequent high level may thus be associated with the decrease of Loligo abundance in the south area (France and Portugal) and the increase in Loligo abundance in the north area (Scotland).
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Population biology of veined squid (Loligo forbesi) and European squid (Loligo vulgaris) from the Portuguese coast
Fisheries Research, 1994Co-Authors: Ana Moreno, Manuela Morais Da Cunha, João PereiraAbstract:Abstract A biological characterisation of the populations of Loligo forbesi and Loligo vulgaris from the Portuguese coast is attempted by analysing morphometric and reproductive data, obtained from 1817 specimens of L. forbesi and 3940 of L. vulgaris , during 1990–1992. Based on the proportions of each of five maturity stages, and the proportion of mated females in monthly samples between January 1990 and June 1992, as well as analyses of the fluctuations of calculated gonadosomatic indices ( GSI ) and maturation indices ( MI ), spawning was found to take place (in autumn and winter for L. forbesi ) throughout the year (for L. vulgaris ), but with peaks of breeding in autumn and winter. Two different size groups at maturity were found in both species, one reaching full maturity at 180 mm dorsal mantle length and the other closer to the maximum size reached by each species and sex. No clear seasonal pattern in sex ratios was observed for either species. Characterisation of the relationship between length and weight in both sexes of both species is given.
M. Begofia Santos - One of the best experts on this subject based on the ideXlab platform.
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Diets of squid Loligo forbesi and Loligo vulgaris in the northeast Atlantic
Fisheries Research, 1994Co-Authors: Graham J. Pierce, Peter Boyle, Lee C. Hastie, M. Begofia SantosAbstract:Abstract Diets of the loliginid squid Loligo forbesi and Loligo vulgaris were investigated by stomach contents sampling during 1990–1993. Monthly samples of Loligo forbesi were collected at Aberdeen and additional samples were obtained from the Irish Sea, Faroe, the English Channel, Vigo, Lisbon and the Azores. Samples of Loligo vulgaris were obtained from Vigo, Barcelona, Lisbon and Faro. Loligo forbesi feeds primarily on fishes, crustaceans and cephalopods. In Scottish waters, Gadidae (mainly Merlangius merlangus and Trisopterus sp.), Ammodytidae and Clupeidae were the most frequently identified prey. The relative importance of fish was slightly higher, and that of crustaceans lower, in the diet of larger squid. Gadidae and Clupeidae were more prominent in the winter diet, with sandeels being taken more frequently in the summer. The same prey taxa were important in the diet of Loligo forbesi across all areas. Fishes occurred in more than 80% of non-empty stomachs except for the Lisbon sample, in which crustaceans were the most frequently identified prey taxon. The species composition of the diet varied between areas. Thus, scad Trachurus picturatus was the most important prey in the Azores. The broad composition of the diet in Loligo vulgaris was similar, although crustaceans were apparently less important, but there were differences in species eaten between areas, and between the two Loligo species. Samples of the ommastrephid squid Todaropsis eblanae taken at Aberdeen indicated that this species was also primarily piscivorous, taking Gadidae and Clupeidae.
