The Mayan octopus (Octopus maya) and the American octopus (O. americanus) are the two species tha... more The Mayan octopus (Octopus maya) and the American octopus (O. americanus) are the two species that support the octopus fishery on the Campeche Bank. The large-scale fleet catches both species. However, landings are recorded as American octopus in the official statistics, and this causes a problem for the management of the fishery. The large-scale octopus fishery on the Campeche Bank was studied using a model based on data from interviews with skippers. A total of 180 valid interviews were conducted in the base ports of Progreso and Yucalpeten (Yucatan), representing 51.1% of the skippers in the fleet in 2019. This information was used for the first time to estimate catch per unit effort (CPUE) and total catches for each octopus species. The mean CPUE ranged between 50 and 500 kg day-1, with minimums of 10 kg day-1. The mean estimated potential catches ranged from 5069 to 3456 t per year for O. maya and from 4113 to 2805 t per year for O. americanus. The relationship between official...
We report a record of the largest known specimen of <em>Ommastrephes bartramii</em>. ... more We report a record of the largest known specimen of <em>Ommastrephes bartramii</em>. It was an almost mature female, with dorsal mantle length (ML) of 1020 mm and weighing around 35 kg, caught by a Spanish fishing vessel in October 2007 on a surface long-line in the Eastern Tropical Pacific. Growth increments on a statolith indicate an age of 492-512 days. The stomach was full and contained beaks of ommastrephid squids and of a small pelagic octopus (<em>Japetella </em>spp.), and remains of mackerel (possibly bait from the long-line) and unidentified fish.
For the beginning of this century it is evident that support for research will be increasingly de... more For the beginning of this century it is evident that support for research will be increasingly dependent upon the results of that research having relevance to society's needs and public benefits. Within this web and coupled with the transfer of scientific knowledge is the opportunity to more effectively explain the society the benefits it receives for its investments in research. This viewpoint paper enlighten the general public on the scientific, industrial and commercial relevance of the research on cephalopods and their parasites. In a comparative analysis with other commercially-important taxa, a historical negligible financial support for research on diseases in this important animal group was noted. Because of that policy-makers on Fisheries Research should balance this public debt in the future
This report summarizes current knowledge on the identification, geographical distribution, nomenc... more This report summarizes current knowledge on the identification, geographical distribution, nomenclature, taxonomy, life history, ecology, and exploitation of cephalopod species of interest to fisheries in European waters. The 17 species range from those currently of significant fishery importance and targeted in at least part of their range (Octopus vulgaris, Sepia officinalis, Loligo vulgaris, Loligo forbesii), through those regularly landed as bycatch (Todaropsis eblanae, Illex coindetii, Eledone cirrhosa, Eledone moschata, Todarodes sagittatus), to those of minor and/or local importance (Alloteuthis subulata, Alloteuthis media, Sepia orbignyana, Sepia elegans, Sepietta oweniana, Sepiola atlantica, Ommastrephes bartramii, Gonatus fabricii). The species reviews aim to provide a concise yet comprehensive account of each, while remaining distinctive from previous and recent accounts. For most of these species, taxonomic status is well resolved, exceptions being the Alloteuthis specie...
This document is a report of an Expert Group under the auspices of the International Council for ... more This document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the view of the Council.
Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out ... more Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out from June to October 2013 in the National Park of the Atlantic Galician Islands (NW Spain). Censuses were undertaken by scuba diving between 5 and 21 m depth in daytime. The total area swept was 13.75 ha. There were no significant differences between octopus presence in dens during open and closed fishing seasons. Depth had a significant negative relationship with occupancy. The average number of dens per 1000 m 2 was 3.84±0.84 in June and 3.89 in October. The area per den was 260 m 2. Den number estimations varied between 1586 and 2057. The largest number of dens (76.5%) was found between 5 and 10 m depth. Den distribution was clumped. No significant differences were found between octopus size classes (small, medium and large) and den diameter. Associate dens were observed. There were no significant differences in den diameter and shell types found around the middens. Many dens could be "permanent". Drilling bivalve shell behaviour is discussed. The surveyed area had around 1100 individuals, mainly small specimens. No significant differences were found between octopus size and depth. Substrate, den type and food abundance and availability (especially razors Ensis arcuatus) seem to be the main factors influencing dens and octopus density and distribution. Den availability does not appear to be a limiting factor in this case. Temperature, den availability, predators and fishing pressure influencing density and distribution are discussed. Rodas inlet may be a preferential habitat for O. vulgaris individuals ranging from 200 to 2000 g, but especially small specimens (≤1000 g).
Sustainable management of exploited stocks demands, among others issues, to identify the spawning... more Sustainable management of exploited stocks demands, among others issues, to identify the spawning spatio-temporal patterns and eventually to protect the spawning grounds of the target species. Squid seems to aggregate at this crucial period of the life-history, which implies increasing vulnerability to fishing. Unlike those of other loliginid species, the spawning preferences of the European squid are largely unknown because finding egg clutches of this species in the wild is challenging. Validated records from research programs are virtually inexistent but unsystematic records from, for example fisherman, suggest that squid spawns regularly on artificial structures. Here, we report for first time a description of the spatio-temporal pattern of squid spawning on artificial devices (ADs). Thirty ADs were deployed over one year at a marine reserve (Cabrera National Park). ADs were distributed covering the three main types of benthic habitat, and ranging from 5 to 50 m depth. ADs were sampled monthly. Three main patters have been evidenced: i) squid would prefer sandy bottoms for spawning, ii) spawning would peak in spring, and iii) squid would expand their spawning areas to shallower waters during the coldest months. It is debatable to extrapolate these patterns to those actually takes place in natural conditions. However, given the heavy fishing effort exerted on squid and data scarcity, the precautionary approach supports to take data from ADs as a starting point for advising sustainable management. Assuming that spawning at ADs and at the wild are correlated, the first pattern may be related to the faster marine currents that prevail on sandy bottoms or the lower abundance of potential predators in these habitats. The second pattern may be related with the typical phytoplanktonzooplankton cascade that, in the Western Mediterranean, takes place just preceding spring. While the third pattern is in accordance with the hypothesis that squid may undergo a spawning migration.
Data on opportunistic sightings of diamond-shaped squid Thysanoteuthis rhombus egg masses in the ... more Data on opportunistic sightings of diamond-shaped squid Thysanoteuthis rhombus egg masses in the Canary Islands (Atlantic Ocean) are presented. A total of 16 egg masses of this species were recorded and photographed from 2000 to 2010 around the western islands of the archipelago (El Hierro, Tenerife and La Gomera). These data reveal the existence of an important spawning area for diamond-shaped squid around the Canary Islands, in subtropical east Atlantic waters. We provide preliminary data for the potential development of an artisanal fishery focused on this species, and a discussion on its potential impacts on the marine ecosystem.
The spatio-temporal distribution of the mesoparasitic copepod Pennella sp. on the short-finned sq... more The spatio-temporal distribution of the mesoparasitic copepod Pennella sp. on the short-finned squid Illex coindetii was studied monthly during 1993 in the southeastern North Atlantic (Galician waters, NW Spain). A total of 600 individuals were analysed separately considering two areas (north and west) with different hydrographical characteristics. Six pennellid stages were found: a copepodite, four chalimus stages and the free-living adult male and female. Epidemiology was assessed using the parasite demographic parameters. The results revealed a marked seasonal pattern in the number of parasites in squid samples from the northern area. This seasonal pattern was not detected in squids from the western area. The observed frequency distributions of parasites on the host population were aggregative at each sampling area. Infection values were extraordinarily high when they are compared with published host-parasite records for other representatives of the genus Pennella. Advantages of the parasite aggregation pattern and possible explanations of the seasonality variations in the number of parasites observed in squid samples from the northern area are discussed.
The common octopus, Octopus vulgaris (Cuvier, 1797), is the most important commercially harvested... more The common octopus, Octopus vulgaris (Cuvier, 1797), is the most important commercially harvested octopus species (Josupeit, 2000). To date, most of the studies published on the O. vulgaris fishery refer to time-series analyses of monthly catches (Quetglas et al., 1998), or trends in landings and effort over a long period of time (Sánchez and Obarti, 1993; Hernández-García et al., 1998; MODELLING O. VULGARIS ARTISANAL FISHERY IN GALICIA 577
The small-scale cuttlefish (Sepia officinalis) fishery in Galician waters (NW Spain) was studied ... more The small-scale cuttlefish (Sepia officinalis) fishery in Galician waters (NW Spain) was studied using a model based on data obtained from fishers. This model was applied using information obtained from the small-scale Galician fleet in 1998. A total of 139 personal interviews were carried out at 62 Galician ports. This information was used to estimate catches per unit effort (CPUE) and total catch for the cuttlefish gillnet fishery. The fleet, which fishes in Galician waters within ICES divisions VIIIc and IXa, was composed of two groups: 600 vessels fishing for cuttlefish in only five months of the year (short season: November to March), and 141 vessels fishing for cuttlefish all year (extended season). Estimated total catch during the fishing season for the whole Galician fleet was 1301 t (869 t short season and 432 t extended season) and average CPUE values were 14.5 kg haul-1 trip-1 vessel-1 (short season) and 12.8 kg haul-1 trip-1 vessel-1 (extended season). To test the reliability of the model, the outputs obtained from the model for a subset of 37 ports (59.7% of all ports) were compared with the official catch statistics for these ports. Differences between total catches estimated by the model and those determined directly at these ports were not significant.
The short-term, meso-scale variability of the mesozooplankton community present in the coastal up... more The short-term, meso-scale variability of the mesozooplankton community present in the coastal upwelling system of the Ría de Vigo (NW Spain) has been analysed. Three well-defined communities were identified: coastal, frontal and oceanic, according to their holoplankton-meroplankton ratio, richness, and total abundance. These communities changed from summer to autumn due to a shift from downwelling to upwelling-favourable conditions coupled with taxa dependent changes in life strategies. Relationships between the resemblance matrix of mesozooplankton and the resemblance matrices of meteorologic, hydrographic and community-derived biotic variables were determined with distance-based linear models (DistLM, 18 variables), showing an increasing amount of explained variability of 6%, 16.1% and 54.5%, respectively. A simplified model revealed that the variability found in the resemblance matrix of mesozooplankton was mainly described by the holoplankton-meroplankton ratio, the total abundance, the influence of lunar cycles, the upwelling index and the richness; altogether accounting for 64% of the total variability. The largest variability of the mesozooplankton resemblance matrix (39.6%) is accounted by the holoplanktonmeroplankton ratio, a simple index that describes appropriately the coastal-ocean gradient. The communities described herein kept their integrity in the studied upwelling and downwelling episodes in spite of the highly advective environment off the Ría de Vigo, presumably due to behavioural changes in the vertical position of the zooplankton.
Proceedings of the Royal Society B: Biological Sciences, 2013
Despite its charismatic appeal to both scientists and the general public, remarkably little is kn... more Despite its charismatic appeal to both scientists and the general public, remarkably little is known about the giant squid Architeuthis , one of the largest of the invertebrates. Although specimens of Architeuthis are becoming more readily available owing to the advancement of deep-sea fishing techniques, considerable controversy exists with regard to topics as varied as their taxonomy, biology and even behaviour. In this study, we have characterized the mitochondrial genome (mitogenome) diversity of 43 Architeuthis samples collected from across the range of the species, in order to use genetic information to provide new and otherwise difficult to obtain insights into the life of this animal. The results show no detectable phylogenetic structure at the mitochondrial level and, furthermore, that the level of nucleotide diversity is exceptionally low. These observations are consistent with the hypotheses that there is only one global species of giant squid, Architeuthis dux (Steenstru...
This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and ... more This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in the tissues of the giant squid Architeuthis dux from the Mediterranean and Atlantic Spanish waters. As for other families of cephalopods, the digestive gland and the branchial hearts of Architeuthis showed the highest concentrations of Ag, Cd, Co, Cu, Fe, Ni, Se, V and Zn, highlighting their major role in the bioaccumulation and detoxification processes. With the exception of Hg, the muscles showed relatively low trace element concentrations. Nevertheless, this tissue contained the main proportion of the total As, Cr, Hg, Mn, Ni, and Zn body burden because muscles represent the main proportion of the squid mass. These findings suggest that the metal metabolism is overall the same as other cephalopod families from neritic waters. In females, Zn concentrations increased in the digestive gland with the squid's weight likely reflecting physiological changes during sexual maturation. Comparing the trace element concentrations in the tissues of Architeuthis, higher Ag, Cu, Hg and Zn concentrations in the squid from the Mediterranean reflected different exposure conditions. In comparison to other meso-pelagic squids from the Bay of Biscay, Cd concentrations recorded in the digestive gland suggest that Architeuthis might feed on more contaminated prey or that it displays a longer life span that other cephalopods.
Planktonic larval dispersal affects the structure, management, and conservation of many fish and ... more Planktonic larval dispersal affects the structure, management, and conservation of many fish and coastal invertebrate populations. The dynamics in coastal upwelling areas favour transport of larvae to the open ocean during upwelling episodes, and concentration of larvae in coastal waters under upwelling relaxation or downwelling conditions. Recent work provides evidence that pelagic larval stages in upwelling areas are influenced by specific larval behaviour, biogeography, and life history parameters among others. Nevertheless, very few of these studies have addressed these findings quantitatively. Here, we present a general approach for assessing the influence of high-frequency upwelling events on Octopus vulgaris planktonic larvae. Specifically, we analyse the rates of change in abundance and biomass of the O. vulgaris early larval phase in the NW Iberian coast, where upwelling events occur with a frequency of 10 to 20 d from April to September. Our analysis indicates that the increase in larval abundance and biomass is significantly correlated with the simultaneous decrease of water column integrated nitrate, ammonium and chlorophyll levels. These conditions occur during the early stage of the relaxation phase of coastal upwelling events, when nutrient salts are consumed to produce biogenic matter, which is retained in the system and transferred through the food web.
Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pi... more Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pierce, G. J. 2010. Life-history traits of the giant squid Architeuthis dux revealed from stable isotope signatures recorded in beaks. – ICES Journal of Marine Science, 67: 1425–1431. Carbon and nitrogen isotope profiles constructed from the upper beaks of four giant squid Architeuthis dux from the Bay of Biscay and Namibian waters provided a time-integrated record of their diet. Values of δ15N ranged from 5.5 to 13.4‰ and of δ13C from −14.4 to −17.8‰. Nitrogen isotope profiles differed significantly in shape among the four animals analysed, but δ15N increased along each profile, with lowest values around the rostral tip. The difference between the lowest and the highest δ15N values was ∼5.8‰, slightly less than a two-level difference between the trophic position of small and large A. dux. The increase in δ13C values was not as pronounced as for the δ15N profiles, but the changes suggest a...
González, Á. F., Otero, J., Pierce, G. J., and Guerra, Á. 2010. Age, growth, and mortality of Lol... more González, Á. F., Otero, J., Pierce, G. J., and Guerra, Á. 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 Ría 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 wer...
We review the variety of existing modelling approaches applied to species habitat mapping and we ... more We review the variety of existing modelling approaches applied to species habitat mapping and we discuss issues arising from the availability and nature of sampled biological data and corresponding ecological and environmental habitat descriptors, as well as the different spatial analysis approaches that are selected according to specific hypotheses. We focus on marine species habitat mapping, presenting an overview of work on modelling fish habitat carried out through a European Communities Policy-Support Action, EnviEFH 'Environmental Approach to Essential Fish Habitat (EFH) Designation' (2005-2008). The selection of the appropriate habitat model is dataset-specific and the resulting EFH maps are often similar in spite of using different models. Derived EFH maps are based on either environmental ranges (used as minimum and maximum environmental habitat descriptors) or probability of occurrence values. We apply model outputs to regions larger than sampled areas making use of the capacity of satellite data to cover wide areas.
Architeuthis dux diet has been analysed according to information available from literature and fr... more Architeuthis dux diet has been analysed according to information available from literature and from the analysis of gut contents of five females and two males from Mediterranean and Atlantic Iberian waters (20 specimens in total). This is the first time that A. dux diet from Atlantic and Mediterranean waters is described. Body weight of specimens ranged from 22.5 to 200 kg. In order to infer common patterns in giant squid diet according to its geographic distribution range, size and sex, available data on their diet composition structure were joined and examined with multivariate techniques. No significant differences in the trophic level on which A. dux prey on were found, considering size, sex and location. Thus, A. dux seems to play the same role in the trophic webs throughout the distribution range examined in this paper, which takes up a very wide geographic area. The trophic level estimated from the diet composition is 4.7. Obtained results show that this species preys mainly on pelagic fast swimmers and shoaling fishes and cephalopods as an opportunistic ambushing hunter.
The Mayan octopus (Octopus maya) and the American octopus (O. americanus) are the two species tha... more The Mayan octopus (Octopus maya) and the American octopus (O. americanus) are the two species that support the octopus fishery on the Campeche Bank. The large-scale fleet catches both species. However, landings are recorded as American octopus in the official statistics, and this causes a problem for the management of the fishery. The large-scale octopus fishery on the Campeche Bank was studied using a model based on data from interviews with skippers. A total of 180 valid interviews were conducted in the base ports of Progreso and Yucalpeten (Yucatan), representing 51.1% of the skippers in the fleet in 2019. This information was used for the first time to estimate catch per unit effort (CPUE) and total catches for each octopus species. The mean CPUE ranged between 50 and 500 kg day-1, with minimums of 10 kg day-1. The mean estimated potential catches ranged from 5069 to 3456 t per year for O. maya and from 4113 to 2805 t per year for O. americanus. The relationship between official...
We report a record of the largest known specimen of <em>Ommastrephes bartramii</em>. ... more We report a record of the largest known specimen of <em>Ommastrephes bartramii</em>. It was an almost mature female, with dorsal mantle length (ML) of 1020 mm and weighing around 35 kg, caught by a Spanish fishing vessel in October 2007 on a surface long-line in the Eastern Tropical Pacific. Growth increments on a statolith indicate an age of 492-512 days. The stomach was full and contained beaks of ommastrephid squids and of a small pelagic octopus (<em>Japetella </em>spp.), and remains of mackerel (possibly bait from the long-line) and unidentified fish.
For the beginning of this century it is evident that support for research will be increasingly de... more For the beginning of this century it is evident that support for research will be increasingly dependent upon the results of that research having relevance to society's needs and public benefits. Within this web and coupled with the transfer of scientific knowledge is the opportunity to more effectively explain the society the benefits it receives for its investments in research. This viewpoint paper enlighten the general public on the scientific, industrial and commercial relevance of the research on cephalopods and their parasites. In a comparative analysis with other commercially-important taxa, a historical negligible financial support for research on diseases in this important animal group was noted. Because of that policy-makers on Fisheries Research should balance this public debt in the future
This report summarizes current knowledge on the identification, geographical distribution, nomenc... more This report summarizes current knowledge on the identification, geographical distribution, nomenclature, taxonomy, life history, ecology, and exploitation of cephalopod species of interest to fisheries in European waters. The 17 species range from those currently of significant fishery importance and targeted in at least part of their range (Octopus vulgaris, Sepia officinalis, Loligo vulgaris, Loligo forbesii), through those regularly landed as bycatch (Todaropsis eblanae, Illex coindetii, Eledone cirrhosa, Eledone moschata, Todarodes sagittatus), to those of minor and/or local importance (Alloteuthis subulata, Alloteuthis media, Sepia orbignyana, Sepia elegans, Sepietta oweniana, Sepiola atlantica, Ommastrephes bartramii, Gonatus fabricii). The species reviews aim to provide a concise yet comprehensive account of each, while remaining distinctive from previous and recent accounts. For most of these species, taxonomic status is well resolved, exceptions being the Alloteuthis specie...
This document is a report of an Expert Group under the auspices of the International Council for ... more This document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the view of the Council.
Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out ... more Four visual censuses targeting Octopus vulgaris living in dens on sandy bottoms were carried out from June to October 2013 in the National Park of the Atlantic Galician Islands (NW Spain). Censuses were undertaken by scuba diving between 5 and 21 m depth in daytime. The total area swept was 13.75 ha. There were no significant differences between octopus presence in dens during open and closed fishing seasons. Depth had a significant negative relationship with occupancy. The average number of dens per 1000 m 2 was 3.84±0.84 in June and 3.89 in October. The area per den was 260 m 2. Den number estimations varied between 1586 and 2057. The largest number of dens (76.5%) was found between 5 and 10 m depth. Den distribution was clumped. No significant differences were found between octopus size classes (small, medium and large) and den diameter. Associate dens were observed. There were no significant differences in den diameter and shell types found around the middens. Many dens could be "permanent". Drilling bivalve shell behaviour is discussed. The surveyed area had around 1100 individuals, mainly small specimens. No significant differences were found between octopus size and depth. Substrate, den type and food abundance and availability (especially razors Ensis arcuatus) seem to be the main factors influencing dens and octopus density and distribution. Den availability does not appear to be a limiting factor in this case. Temperature, den availability, predators and fishing pressure influencing density and distribution are discussed. Rodas inlet may be a preferential habitat for O. vulgaris individuals ranging from 200 to 2000 g, but especially small specimens (≤1000 g).
Sustainable management of exploited stocks demands, among others issues, to identify the spawning... more Sustainable management of exploited stocks demands, among others issues, to identify the spawning spatio-temporal patterns and eventually to protect the spawning grounds of the target species. Squid seems to aggregate at this crucial period of the life-history, which implies increasing vulnerability to fishing. Unlike those of other loliginid species, the spawning preferences of the European squid are largely unknown because finding egg clutches of this species in the wild is challenging. Validated records from research programs are virtually inexistent but unsystematic records from, for example fisherman, suggest that squid spawns regularly on artificial structures. Here, we report for first time a description of the spatio-temporal pattern of squid spawning on artificial devices (ADs). Thirty ADs were deployed over one year at a marine reserve (Cabrera National Park). ADs were distributed covering the three main types of benthic habitat, and ranging from 5 to 50 m depth. ADs were sampled monthly. Three main patters have been evidenced: i) squid would prefer sandy bottoms for spawning, ii) spawning would peak in spring, and iii) squid would expand their spawning areas to shallower waters during the coldest months. It is debatable to extrapolate these patterns to those actually takes place in natural conditions. However, given the heavy fishing effort exerted on squid and data scarcity, the precautionary approach supports to take data from ADs as a starting point for advising sustainable management. Assuming that spawning at ADs and at the wild are correlated, the first pattern may be related to the faster marine currents that prevail on sandy bottoms or the lower abundance of potential predators in these habitats. The second pattern may be related with the typical phytoplanktonzooplankton cascade that, in the Western Mediterranean, takes place just preceding spring. While the third pattern is in accordance with the hypothesis that squid may undergo a spawning migration.
Data on opportunistic sightings of diamond-shaped squid Thysanoteuthis rhombus egg masses in the ... more Data on opportunistic sightings of diamond-shaped squid Thysanoteuthis rhombus egg masses in the Canary Islands (Atlantic Ocean) are presented. A total of 16 egg masses of this species were recorded and photographed from 2000 to 2010 around the western islands of the archipelago (El Hierro, Tenerife and La Gomera). These data reveal the existence of an important spawning area for diamond-shaped squid around the Canary Islands, in subtropical east Atlantic waters. We provide preliminary data for the potential development of an artisanal fishery focused on this species, and a discussion on its potential impacts on the marine ecosystem.
The spatio-temporal distribution of the mesoparasitic copepod Pennella sp. on the short-finned sq... more The spatio-temporal distribution of the mesoparasitic copepod Pennella sp. on the short-finned squid Illex coindetii was studied monthly during 1993 in the southeastern North Atlantic (Galician waters, NW Spain). A total of 600 individuals were analysed separately considering two areas (north and west) with different hydrographical characteristics. Six pennellid stages were found: a copepodite, four chalimus stages and the free-living adult male and female. Epidemiology was assessed using the parasite demographic parameters. The results revealed a marked seasonal pattern in the number of parasites in squid samples from the northern area. This seasonal pattern was not detected in squids from the western area. The observed frequency distributions of parasites on the host population were aggregative at each sampling area. Infection values were extraordinarily high when they are compared with published host-parasite records for other representatives of the genus Pennella. Advantages of the parasite aggregation pattern and possible explanations of the seasonality variations in the number of parasites observed in squid samples from the northern area are discussed.
The common octopus, Octopus vulgaris (Cuvier, 1797), is the most important commercially harvested... more The common octopus, Octopus vulgaris (Cuvier, 1797), is the most important commercially harvested octopus species (Josupeit, 2000). To date, most of the studies published on the O. vulgaris fishery refer to time-series analyses of monthly catches (Quetglas et al., 1998), or trends in landings and effort over a long period of time (Sánchez and Obarti, 1993; Hernández-García et al., 1998; MODELLING O. VULGARIS ARTISANAL FISHERY IN GALICIA 577
The small-scale cuttlefish (Sepia officinalis) fishery in Galician waters (NW Spain) was studied ... more The small-scale cuttlefish (Sepia officinalis) fishery in Galician waters (NW Spain) was studied using a model based on data obtained from fishers. This model was applied using information obtained from the small-scale Galician fleet in 1998. A total of 139 personal interviews were carried out at 62 Galician ports. This information was used to estimate catches per unit effort (CPUE) and total catch for the cuttlefish gillnet fishery. The fleet, which fishes in Galician waters within ICES divisions VIIIc and IXa, was composed of two groups: 600 vessels fishing for cuttlefish in only five months of the year (short season: November to March), and 141 vessels fishing for cuttlefish all year (extended season). Estimated total catch during the fishing season for the whole Galician fleet was 1301 t (869 t short season and 432 t extended season) and average CPUE values were 14.5 kg haul-1 trip-1 vessel-1 (short season) and 12.8 kg haul-1 trip-1 vessel-1 (extended season). To test the reliability of the model, the outputs obtained from the model for a subset of 37 ports (59.7% of all ports) were compared with the official catch statistics for these ports. Differences between total catches estimated by the model and those determined directly at these ports were not significant.
The short-term, meso-scale variability of the mesozooplankton community present in the coastal up... more The short-term, meso-scale variability of the mesozooplankton community present in the coastal upwelling system of the Ría de Vigo (NW Spain) has been analysed. Three well-defined communities were identified: coastal, frontal and oceanic, according to their holoplankton-meroplankton ratio, richness, and total abundance. These communities changed from summer to autumn due to a shift from downwelling to upwelling-favourable conditions coupled with taxa dependent changes in life strategies. Relationships between the resemblance matrix of mesozooplankton and the resemblance matrices of meteorologic, hydrographic and community-derived biotic variables were determined with distance-based linear models (DistLM, 18 variables), showing an increasing amount of explained variability of 6%, 16.1% and 54.5%, respectively. A simplified model revealed that the variability found in the resemblance matrix of mesozooplankton was mainly described by the holoplankton-meroplankton ratio, the total abundance, the influence of lunar cycles, the upwelling index and the richness; altogether accounting for 64% of the total variability. The largest variability of the mesozooplankton resemblance matrix (39.6%) is accounted by the holoplanktonmeroplankton ratio, a simple index that describes appropriately the coastal-ocean gradient. The communities described herein kept their integrity in the studied upwelling and downwelling episodes in spite of the highly advective environment off the Ría de Vigo, presumably due to behavioural changes in the vertical position of the zooplankton.
Proceedings of the Royal Society B: Biological Sciences, 2013
Despite its charismatic appeal to both scientists and the general public, remarkably little is kn... more Despite its charismatic appeal to both scientists and the general public, remarkably little is known about the giant squid Architeuthis , one of the largest of the invertebrates. Although specimens of Architeuthis are becoming more readily available owing to the advancement of deep-sea fishing techniques, considerable controversy exists with regard to topics as varied as their taxonomy, biology and even behaviour. In this study, we have characterized the mitochondrial genome (mitogenome) diversity of 43 Architeuthis samples collected from across the range of the species, in order to use genetic information to provide new and otherwise difficult to obtain insights into the life of this animal. The results show no detectable phylogenetic structure at the mitochondrial level and, furthermore, that the level of nucleotide diversity is exceptionally low. These observations are consistent with the hypotheses that there is only one global species of giant squid, Architeuthis dux (Steenstru...
This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and ... more This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in the tissues of the giant squid Architeuthis dux from the Mediterranean and Atlantic Spanish waters. As for other families of cephalopods, the digestive gland and the branchial hearts of Architeuthis showed the highest concentrations of Ag, Cd, Co, Cu, Fe, Ni, Se, V and Zn, highlighting their major role in the bioaccumulation and detoxification processes. With the exception of Hg, the muscles showed relatively low trace element concentrations. Nevertheless, this tissue contained the main proportion of the total As, Cr, Hg, Mn, Ni, and Zn body burden because muscles represent the main proportion of the squid mass. These findings suggest that the metal metabolism is overall the same as other cephalopod families from neritic waters. In females, Zn concentrations increased in the digestive gland with the squid's weight likely reflecting physiological changes during sexual maturation. Comparing the trace element concentrations in the tissues of Architeuthis, higher Ag, Cu, Hg and Zn concentrations in the squid from the Mediterranean reflected different exposure conditions. In comparison to other meso-pelagic squids from the Bay of Biscay, Cd concentrations recorded in the digestive gland suggest that Architeuthis might feed on more contaminated prey or that it displays a longer life span that other cephalopods.
Planktonic larval dispersal affects the structure, management, and conservation of many fish and ... more Planktonic larval dispersal affects the structure, management, and conservation of many fish and coastal invertebrate populations. The dynamics in coastal upwelling areas favour transport of larvae to the open ocean during upwelling episodes, and concentration of larvae in coastal waters under upwelling relaxation or downwelling conditions. Recent work provides evidence that pelagic larval stages in upwelling areas are influenced by specific larval behaviour, biogeography, and life history parameters among others. Nevertheless, very few of these studies have addressed these findings quantitatively. Here, we present a general approach for assessing the influence of high-frequency upwelling events on Octopus vulgaris planktonic larvae. Specifically, we analyse the rates of change in abundance and biomass of the O. vulgaris early larval phase in the NW Iberian coast, where upwelling events occur with a frequency of 10 to 20 d from April to September. Our analysis indicates that the increase in larval abundance and biomass is significantly correlated with the simultaneous decrease of water column integrated nitrate, ammonium and chlorophyll levels. These conditions occur during the early stage of the relaxation phase of coastal upwelling events, when nutrient salts are consumed to produce biogenic matter, which is retained in the system and transferred through the food web.
Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pi... more Guerra, Á., Rodríguez-Navarro, A. B., González, Á. F., Romanek, C. S., Álvarez-Lloret, P., and Pierce, G. J. 2010. Life-history traits of the giant squid Architeuthis dux revealed from stable isotope signatures recorded in beaks. – ICES Journal of Marine Science, 67: 1425–1431. Carbon and nitrogen isotope profiles constructed from the upper beaks of four giant squid Architeuthis dux from the Bay of Biscay and Namibian waters provided a time-integrated record of their diet. Values of δ15N ranged from 5.5 to 13.4‰ and of δ13C from −14.4 to −17.8‰. Nitrogen isotope profiles differed significantly in shape among the four animals analysed, but δ15N increased along each profile, with lowest values around the rostral tip. The difference between the lowest and the highest δ15N values was ∼5.8‰, slightly less than a two-level difference between the trophic position of small and large A. dux. The increase in δ13C values was not as pronounced as for the δ15N profiles, but the changes suggest a...
González, Á. F., Otero, J., Pierce, G. J., and Guerra, Á. 2010. Age, growth, and mortality of Lol... more González, Á. F., Otero, J., Pierce, G. J., and Guerra, Á. 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 Ría 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 wer...
We review the variety of existing modelling approaches applied to species habitat mapping and we ... more We review the variety of existing modelling approaches applied to species habitat mapping and we discuss issues arising from the availability and nature of sampled biological data and corresponding ecological and environmental habitat descriptors, as well as the different spatial analysis approaches that are selected according to specific hypotheses. We focus on marine species habitat mapping, presenting an overview of work on modelling fish habitat carried out through a European Communities Policy-Support Action, EnviEFH 'Environmental Approach to Essential Fish Habitat (EFH) Designation' (2005-2008). The selection of the appropriate habitat model is dataset-specific and the resulting EFH maps are often similar in spite of using different models. Derived EFH maps are based on either environmental ranges (used as minimum and maximum environmental habitat descriptors) or probability of occurrence values. We apply model outputs to regions larger than sampled areas making use of the capacity of satellite data to cover wide areas.
Architeuthis dux diet has been analysed according to information available from literature and fr... more Architeuthis dux diet has been analysed according to information available from literature and from the analysis of gut contents of five females and two males from Mediterranean and Atlantic Iberian waters (20 specimens in total). This is the first time that A. dux diet from Atlantic and Mediterranean waters is described. Body weight of specimens ranged from 22.5 to 200 kg. In order to infer common patterns in giant squid diet according to its geographic distribution range, size and sex, available data on their diet composition structure were joined and examined with multivariate techniques. No significant differences in the trophic level on which A. dux prey on were found, considering size, sex and location. Thus, A. dux seems to play the same role in the trophic webs throughout the distribution range examined in this paper, which takes up a very wide geographic area. The trophic level estimated from the diet composition is 4.7. Obtained results show that this species preys mainly on pelagic fast swimmers and shoaling fishes and cephalopods as an opportunistic ambushing hunter.
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Papers by ANGEL GUERRA