Pablo Abaunza - Academia.edu (original) (raw)
Papers by Pablo Abaunza
SpringerBriefs in biology, 2019
The management of bluefin tuna resources within ICCAT is based on the consideration of two distin... more The management of bluefin tuna resources within ICCAT is based on the consideration of two distinct stocks. A definition is provided of what a stock is from the point of view of a species subjected to fishing exploitation and the basic criterion by which the separation of bluefin tuna into western and eastern stocks was adopted. For the purposes of resource management, the International Commission for the Conservation of Atlantic Tunas (ICCAT) considers the population of the North Atlantic as two stocks 1 : the eastern, which includes the Mediterranean, and the western (ICCAT 2010). These are managed separately. The line defining the separation of the stocks is the 45°W meridian (Fig. 3.1). The basis on which this separation of eastern and western stocks is made is the fact that there are two main spawning areas, one in the Gulf of Mexico and the other in the Mediterranean. This dividing line in no way means that ABFT cannot cross it; they do so without any difficulty as demonstrated in several articles:
SpringerBriefs in biology, 2019
The Strait of Gibraltar is defined as one of the most emblematic places in bluefin tuna biology, ... more The Strait of Gibraltar is defined as one of the most emblematic places in bluefin tuna biology, and the traps installed therein are platforms without equal in the study of this species. The enormous literature available on his fishing gear makes it impossible to make a full description from the historical point of view in the present study; however, some of the scientific activities and scientific committees of the last century are cited, followed by a list of the most recent research projects on the species. Two symposia, held in 2008 and 2011, dealing with bluefin tuna biology and fishing are reported, the latter of which was exclusively dedicated to the traps fishery and the research carried out at these fishing installations.
Following an extensive description and review of the bibliography of the overall situation of the... more Following an extensive description and review of the bibliography of the overall situation of the bluefin tuna, Thunnus thynnus (L.), ABFT, from ancient times until the present, the eastern Atlantic fisheries that traditionally caught ABFT spawners (traps of the Strait of Gibraltar and northern European fisheries) are described with the aim of explaining the reasons behind their decline from the 1960s. The study includes the fishery of the Bay of Biscay, an area where small and medium-sized spawners migrated towards areas of trophic concentration in the north of Europe. The fisheries of ABFT juveniles began to develop in the eastern Atlantic at the end of the 1940s (Bay of Biscay) and the middle of the 1950s (off the coast of Morocco). The results of an analysis of the juvenile ABFT population of the eastern Atlantic part between 1949 and 1962 reveal that under different scenarios the high fishing mortality exerted on the juvenile fish groups (<5 years) in the period studied may have been one of the main factors behind the decline of the north eastern Atlantic fisheries of spawners from 1963. Juvenile catches of that magnitude (6,879,967 ABFT) may have given rise to the limited recruitment from juvenile age to spawning stocks. The analysis has also been made for the periods 1970–2006 and the present (2009). In the first of these two cases, fishing mortality (F) fell as a result of a fall in the catch of juveniles, mainly the fishery of Morocco. Nevertheless, during these years, over 4 million specimens of 1 year were caught illegally in the Atlantic part of the eastern stock. The fall in F is now even greater due to the practically entire disappearance of the juvenile fisheries as a result of the implementation of the Pluriannual Recovery Plan (PRP) of the International Commission for the Conservation of Atlantic Tunas (ICCAT), which began in the fisheries of the eastern stock in 2007.
Journal of Parasitic Diseases, Jul 31, 2021
Information on the distribution and abundance patterns of trematodes are essential to reveal the ... more Information on the distribution and abundance patterns of trematodes are essential to reveal the ecology of host–parasite interactions. The Western Ghats of India, a biodiversity hotspot, is rich in freshwater fish diversity and endemism. Though there are several studies on various other aspects of fish ecology, studies on their parasitic fauna is meager. The objective of the present study is to explore the distribution and infection patterns of metacercariae of five species of trematodes in the freshwater fishes, Haludaria fasciata and Pseudosphromenus cupanus. The infection parameters were analyzed for each host and CART model was applied to analyze the environmental factors affecting parasite distribution patterns. All species of metacercariae showed an over-dispersed aggregate distributions. The classification tree models indicated that among the environmental factors considered, differences in host locality was the most influential factor in both fishes, followed at a greater distance by the factor seasonality. The parasite communities exhibited temporal and spatial differences in the infection pattern in response to seasonal and locational variations.
Elsevier eBooks, 2014
Abstract This chapter provides a guide for parasitologists and fishery biologists to the use of p... more Abstract This chapter provides a guide for parasitologists and fishery biologists to the use of parasites as biological tags for stock identification of marine fish. Parasite tags have certain advantages over other methods of stock identification, but they also have their limitations, so we strongly recommend an interdisciplinary approach in which the results from different methods are compared and used to complement one another. Some biological features to consider in the selection of a good tag parasite are described here, but these should be regarded as guidelines rather than strict criteria. Two different approaches to the use of parasites as biological tags are described, one in which a large number of fish are examined for a small number of parasite taxa and the other in which entire parasite assemblages are analyzed using multivariate statistical methods. Example case studies are given, which are representative of the two approaches. The statistical methods applied to parasite infection data tag studies are described and discussed, with references to studies in which they have been used. Recommendations are given for the collection of hosts and parasites to ensure that parasites are collected in the best possible condition, and methods for the preparation of parasites for examination are described. Parasite groups requiring special attention in their collection and preparation are highlighted, and publications giving identification keys to different taxonomic groups of parasites are provided. There is also a section dealing with the interpretation of results in terms of stock identification.
Industrias Pesqueras: revista marítima quincenal, 2015
Bulletin of The European Association of Fish Pathologists, Jan 20, 2004
This checklist was compiled from both the literature and from the results of an unpublished surve... more This checklist was compiled from both the literature and from the results of an unpublished survey of the parasite faunas of Lophius piscatorius and L. budegassa carried out by the authors. Sixty-nine named species, plus many other parasites reported under generic or higher taxonomic names only, have been recorded from these two host species. Sixty-two named species have been recorded from L. piscatorius, five species being new host records from our survey. Twenty-two named species have been recorded from L. budegassa, all but eight of which are new host records from our survey. Fifteen parasite species are common to both host species. The greater diversity of the recorded parasite fauna of L. piscatorius compared to that of L. budegassa may be due to the fact that L. piscatorius has been the subject of more studies than L. budegassa. Another possible explanation is that L. budegassa may frequently have been misidentified as L. piscatorius, especially in the earlier literature.
Journal of Helminthology, Jun 1, 2007
In the present paper, recent results obtained on the use of different distributions observed in l... more In the present paper, recent results obtained on the use of different distributions observed in larval species of Anisakis, genetically identified by means of allozyme markers, for stock characterization of demersal (Merluccius merluccius), small (Trachurus trachurus) and large pelagic (Xiphias gladius) finfish species in European waters, are reviewed and discussed. Several species of Anisakis were identified in the three fish hosts: A. simplex (s.s.), A. physeteris, A. typica, A. ziphidarum,A. pegreffii, A. brevispiculata and A. paggiae. Canonical discriminant analysis performed on all the samples of the three fish species collected in areas comprising their geographical range, according to the different species of Anisakis identified, showed distinct fish populations in European waters. In all the three fish hosts, the pattern of distribution of Anisakis larvae allowed discrimination of Mediterranean stocks from Atlantic stocks. In the case of swordfish, the possible existence of a southern Atlantic stock separated from a northern one is also suggested. Congruence and discordance with the population genetic data inferred from allozyme markers on the same samples of the three fish species are also discussed.
Industrias Pesqueras: revista marítima quincenal, 2018
Parasitology, Aug 22, 2014
The unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. St... more The unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. Stock identification of Mediterranean fisheries has been based mostly from data on biology, morphometrics, artificial tags, otolith shape and fish genetics, with less effort on the use of parasites as biomarkers. Here we use some case studies comparing Mediterranean vs Atlantic fish stocks in a multidisciplinary framework. The generalized Procrustes Rotation (PR) was used to assess the association between host genetics and larval Anisakis spp. datasets on demersal (hake) and pelagic (horse mackerel, swordfish) species. When discordant results emerged, they were due to the different features of the data. While fish population genetics can detect changes over an evolutionary timescale, providing indications on the cohesive action of gene flow, parasites are more suitable biomarkers when considering fish stocks over smaller temporal and spatial scales, hence giving information of fish movements over their lifespan. Future studies on the phylogeographic analysis of parasites suitable as biomarkers, and that of their fish host, performed on the same genes, will represent a further tool to be included in multidisciplinary studies on fish stock structure.
Frontiers in Marine Science, Jul 17, 2023
Managing a multi-species fishery in distant waters: the case of the Spanish-flagged purse seine f... more Managing a multi-species fishery in distant waters: the case of the Spanish-flagged purse seine fishery targeting tropical tuna in the Indian Ocean.
A brief description is made of the Atlantic bluefin tuna, Thunnus thynnus (L.), from the point of... more A brief description is made of the Atlantic bluefin tuna, Thunnus thynnus (L.), from the point of view of its biology, geographic distribution and population dynamic. With the Strait of Gibraltar traps as a reference and providing a vision from ancient times to the present, scientific activities on this fishing gear are reviewed in an attempt to explain the reasons behind the crisis of the catches in this fishery, which began at the beginning of the 1960s and which has been extended until recent times. In order to do so and based on a recent publication on the issue, the Bay of Biscay fishery is presented as a fishery with a long tradition on which numerous scientific studies have been carried out and whose data are of great importance in the ABFT assessment group of SCRS (ICCAT's scientific committee). Traditionally, the catches of this fishery have been made up of juvenile specimens (<40 kg) making up more than 97% in number of fishes according to a 62-year series studied (1949-2010). From an analysis of the population, it has been shown that the impact of massive fishing of juveniles in this fishery between 1949 and 1962, together with that of juveniles in Morocco (the Atlantic part) possibly caused the decline of the traditional traps fishery of spawners in the Strait of Gibraltar and the collapse of the spawner fisheries in the north of Europe from the 1960s. This situation continued until 2007, the year from which a Pluri-Annual Recovery Plan (PARP) was adopted by ICCAT for the eastern stock. Since the PARP was implemented, juvenile catches have disappeared from almost all the fisheries, a scenario that coincides with a considerable recovery of the spawning stock biomass in the easter Atlantic and Mediterranean, according to the results of the latest SCRS assessments. Keywords Atlantic Bluefin Tuna Á Traps Á Strait of Gibraltar Á Bay of Biscay Á Juveniles Fishing xi Chapter 1
Scientific advice on the concept of surplus, as defined by the UNCLOS, was provided for three typ... more Scientific advice on the concept of surplus, as defined by the UNCLOS, was provided for three types of Sustainable Fisheries Partnership Agreements (SFPAs): i) Mixed SFPAs in West Africa, ii) Tuna SFPAs and iii) SFPA with Greenland. For Mixed SFPAs in West Africa, methods for surplus computation were defined, including alternatives for cases of data limited stocks. These methods may use as input five parameters that could be obtained from those recent stocks assessments that are representative of the current stock status. Surplus estimates would need to be regularly updated (ideally, yearly), according to every new stock assessments and following the enforcement of a management plan (or, by default, according to a transition scheme towards reaching Fmsy in 2020). In the case of West African transboundary stocks, a theoretical share of the surplus could be calculated using a standard rule based on historical catches within EEZs. The Surplus concept is not applicable for Tuna SFPAs, d...
Parasitology International, 2021
Parasitic castration is a phenomenon where the parasite blocks or reduces the host reproductive o... more Parasitic castration is a phenomenon where the parasite blocks or reduces the host reproductive output. This study explored the impact of Tetracotyle wayanadensis infection on the reproductive performance of the freshwater fish Aplocheilus lineatus. Heavily infected A. lineatus showed slow and sluggish movements with reduced food intake and feeding activities. Histopathological observations of the ovary revealed severe necrosis and degeneration of previtellogenic and vitellogenic oocytes and follicular atresia. The oogonial nests were absent; chromatin nucleolar oocytes irregularly shaped and vacuolated. Perinucleolar oocytes have a vacuolated appearance with the hypertrophied highly columnar follicular cells invading them. Vitellogenic oocytes had a shrunken appearance with folded zona radiata; yolk globules broken down into smaller granules together with vacuolar degeneration of the ooplasm. The hypertrophied highly columnar follicular cells invaded the early vitellogenic oocytes to phagocytize the degenerating material. Zona radiata was found broken and liquefaction of yolk globules was evident with advancement in follicular atresia. Seasonal variation of parasitic infection has also been studied. Metacercaria infecting the vital organs showed seasonal variation with the highest values for prevalence and abundance during monsoon and mean intensity during winter. The lowest values for these descriptors were documented during the post-monsoon period.
In ordinary catch at age models, natural mortality conditions and determines the catchabilities a... more In ordinary catch at age models, natural mortality conditions and determines the catchabilities at age obtained for the surveys which tune the assessments. For the same reason, inferring the Natural mortality of a fish stock from surveys' estimates, require some assumption of the survey catchabilities at age. The anchovy fishery in the Bay of Biscay has been closed since 2005 up to 2010, due to low biomass levels. In the mean time, and since 1989, the population has been directly monitored by two independent surveys, acoustic and egg (DEPM) surveys, which supplied the basic information for the assessment of this stock carried out by ICES. The closure of the fishery supposes a major contrast on total mortality levels affecting the population in comparison with the former period of exploitation, suitable to get estimates of Natural and Fishing mortalities, under the assumption of no major changes in M occurring between both periods. Log linear models and a seasonal integrate catch at age analysis were tuned to the fishery and two series of surveys under the assumption of constant catchabilities across ages for the two surveys' population estimates. An analysis of the period 1987-2009, searching for a single and constant natural mortality at age, results in minimum residual SSQ for an M around 0.8. But a better result is obtained when a pattern of increasing natural mortality at age is allowed, a possibility suggested since a long time for this type of short living species.
Se ha medido el diámetro del núcleo de otolitos de anchoa, Engraulis encrasicolus (Linnaeus, 1758... more Se ha medido el diámetro del núcleo de otolitos de anchoa, Engraulis encrasicolus (Linnaeus, 1758), recogidos en el Cantábrico oriental, en el occidental y en Galicia durante 1995 y 1998 para comprobar si existían diferencias en su longitud y, si era así, si estas diferencias eran características de los grupos de población de la especie. Los resultados muestran diferencias significativas entre las tres regiones y, aunque deben considerarse solamente como preliminares, parecen indicar que estas diferencias pueden ser propias de los grupos de población de anchoa descritos en las regiones estudiadas.
SpringerBriefs in biology, 2019
The management of bluefin tuna resources within ICCAT is based on the consideration of two distin... more The management of bluefin tuna resources within ICCAT is based on the consideration of two distinct stocks. A definition is provided of what a stock is from the point of view of a species subjected to fishing exploitation and the basic criterion by which the separation of bluefin tuna into western and eastern stocks was adopted. For the purposes of resource management, the International Commission for the Conservation of Atlantic Tunas (ICCAT) considers the population of the North Atlantic as two stocks 1 : the eastern, which includes the Mediterranean, and the western (ICCAT 2010). These are managed separately. The line defining the separation of the stocks is the 45°W meridian (Fig. 3.1). The basis on which this separation of eastern and western stocks is made is the fact that there are two main spawning areas, one in the Gulf of Mexico and the other in the Mediterranean. This dividing line in no way means that ABFT cannot cross it; they do so without any difficulty as demonstrated in several articles:
SpringerBriefs in biology, 2019
The Strait of Gibraltar is defined as one of the most emblematic places in bluefin tuna biology, ... more The Strait of Gibraltar is defined as one of the most emblematic places in bluefin tuna biology, and the traps installed therein are platforms without equal in the study of this species. The enormous literature available on his fishing gear makes it impossible to make a full description from the historical point of view in the present study; however, some of the scientific activities and scientific committees of the last century are cited, followed by a list of the most recent research projects on the species. Two symposia, held in 2008 and 2011, dealing with bluefin tuna biology and fishing are reported, the latter of which was exclusively dedicated to the traps fishery and the research carried out at these fishing installations.
Following an extensive description and review of the bibliography of the overall situation of the... more Following an extensive description and review of the bibliography of the overall situation of the bluefin tuna, Thunnus thynnus (L.), ABFT, from ancient times until the present, the eastern Atlantic fisheries that traditionally caught ABFT spawners (traps of the Strait of Gibraltar and northern European fisheries) are described with the aim of explaining the reasons behind their decline from the 1960s. The study includes the fishery of the Bay of Biscay, an area where small and medium-sized spawners migrated towards areas of trophic concentration in the north of Europe. The fisheries of ABFT juveniles began to develop in the eastern Atlantic at the end of the 1940s (Bay of Biscay) and the middle of the 1950s (off the coast of Morocco). The results of an analysis of the juvenile ABFT population of the eastern Atlantic part between 1949 and 1962 reveal that under different scenarios the high fishing mortality exerted on the juvenile fish groups (<5 years) in the period studied may have been one of the main factors behind the decline of the north eastern Atlantic fisheries of spawners from 1963. Juvenile catches of that magnitude (6,879,967 ABFT) may have given rise to the limited recruitment from juvenile age to spawning stocks. The analysis has also been made for the periods 1970–2006 and the present (2009). In the first of these two cases, fishing mortality (F) fell as a result of a fall in the catch of juveniles, mainly the fishery of Morocco. Nevertheless, during these years, over 4 million specimens of 1 year were caught illegally in the Atlantic part of the eastern stock. The fall in F is now even greater due to the practically entire disappearance of the juvenile fisheries as a result of the implementation of the Pluriannual Recovery Plan (PRP) of the International Commission for the Conservation of Atlantic Tunas (ICCAT), which began in the fisheries of the eastern stock in 2007.
Journal of Parasitic Diseases, Jul 31, 2021
Information on the distribution and abundance patterns of trematodes are essential to reveal the ... more Information on the distribution and abundance patterns of trematodes are essential to reveal the ecology of host–parasite interactions. The Western Ghats of India, a biodiversity hotspot, is rich in freshwater fish diversity and endemism. Though there are several studies on various other aspects of fish ecology, studies on their parasitic fauna is meager. The objective of the present study is to explore the distribution and infection patterns of metacercariae of five species of trematodes in the freshwater fishes, Haludaria fasciata and Pseudosphromenus cupanus. The infection parameters were analyzed for each host and CART model was applied to analyze the environmental factors affecting parasite distribution patterns. All species of metacercariae showed an over-dispersed aggregate distributions. The classification tree models indicated that among the environmental factors considered, differences in host locality was the most influential factor in both fishes, followed at a greater distance by the factor seasonality. The parasite communities exhibited temporal and spatial differences in the infection pattern in response to seasonal and locational variations.
Elsevier eBooks, 2014
Abstract This chapter provides a guide for parasitologists and fishery biologists to the use of p... more Abstract This chapter provides a guide for parasitologists and fishery biologists to the use of parasites as biological tags for stock identification of marine fish. Parasite tags have certain advantages over other methods of stock identification, but they also have their limitations, so we strongly recommend an interdisciplinary approach in which the results from different methods are compared and used to complement one another. Some biological features to consider in the selection of a good tag parasite are described here, but these should be regarded as guidelines rather than strict criteria. Two different approaches to the use of parasites as biological tags are described, one in which a large number of fish are examined for a small number of parasite taxa and the other in which entire parasite assemblages are analyzed using multivariate statistical methods. Example case studies are given, which are representative of the two approaches. The statistical methods applied to parasite infection data tag studies are described and discussed, with references to studies in which they have been used. Recommendations are given for the collection of hosts and parasites to ensure that parasites are collected in the best possible condition, and methods for the preparation of parasites for examination are described. Parasite groups requiring special attention in their collection and preparation are highlighted, and publications giving identification keys to different taxonomic groups of parasites are provided. There is also a section dealing with the interpretation of results in terms of stock identification.
Industrias Pesqueras: revista marítima quincenal, 2015
Bulletin of The European Association of Fish Pathologists, Jan 20, 2004
This checklist was compiled from both the literature and from the results of an unpublished surve... more This checklist was compiled from both the literature and from the results of an unpublished survey of the parasite faunas of Lophius piscatorius and L. budegassa carried out by the authors. Sixty-nine named species, plus many other parasites reported under generic or higher taxonomic names only, have been recorded from these two host species. Sixty-two named species have been recorded from L. piscatorius, five species being new host records from our survey. Twenty-two named species have been recorded from L. budegassa, all but eight of which are new host records from our survey. Fifteen parasite species are common to both host species. The greater diversity of the recorded parasite fauna of L. piscatorius compared to that of L. budegassa may be due to the fact that L. piscatorius has been the subject of more studies than L. budegassa. Another possible explanation is that L. budegassa may frequently have been misidentified as L. piscatorius, especially in the earlier literature.
Journal of Helminthology, Jun 1, 2007
In the present paper, recent results obtained on the use of different distributions observed in l... more In the present paper, recent results obtained on the use of different distributions observed in larval species of Anisakis, genetically identified by means of allozyme markers, for stock characterization of demersal (Merluccius merluccius), small (Trachurus trachurus) and large pelagic (Xiphias gladius) finfish species in European waters, are reviewed and discussed. Several species of Anisakis were identified in the three fish hosts: A. simplex (s.s.), A. physeteris, A. typica, A. ziphidarum,A. pegreffii, A. brevispiculata and A. paggiae. Canonical discriminant analysis performed on all the samples of the three fish species collected in areas comprising their geographical range, according to the different species of Anisakis identified, showed distinct fish populations in European waters. In all the three fish hosts, the pattern of distribution of Anisakis larvae allowed discrimination of Mediterranean stocks from Atlantic stocks. In the case of swordfish, the possible existence of a southern Atlantic stock separated from a northern one is also suggested. Congruence and discordance with the population genetic data inferred from allozyme markers on the same samples of the three fish species are also discussed.
Industrias Pesqueras: revista marítima quincenal, 2018
Parasitology, Aug 22, 2014
The unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. St... more The unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. Stock identification of Mediterranean fisheries has been based mostly from data on biology, morphometrics, artificial tags, otolith shape and fish genetics, with less effort on the use of parasites as biomarkers. Here we use some case studies comparing Mediterranean vs Atlantic fish stocks in a multidisciplinary framework. The generalized Procrustes Rotation (PR) was used to assess the association between host genetics and larval Anisakis spp. datasets on demersal (hake) and pelagic (horse mackerel, swordfish) species. When discordant results emerged, they were due to the different features of the data. While fish population genetics can detect changes over an evolutionary timescale, providing indications on the cohesive action of gene flow, parasites are more suitable biomarkers when considering fish stocks over smaller temporal and spatial scales, hence giving information of fish movements over their lifespan. Future studies on the phylogeographic analysis of parasites suitable as biomarkers, and that of their fish host, performed on the same genes, will represent a further tool to be included in multidisciplinary studies on fish stock structure.
Frontiers in Marine Science, Jul 17, 2023
Managing a multi-species fishery in distant waters: the case of the Spanish-flagged purse seine f... more Managing a multi-species fishery in distant waters: the case of the Spanish-flagged purse seine fishery targeting tropical tuna in the Indian Ocean.
A brief description is made of the Atlantic bluefin tuna, Thunnus thynnus (L.), from the point of... more A brief description is made of the Atlantic bluefin tuna, Thunnus thynnus (L.), from the point of view of its biology, geographic distribution and population dynamic. With the Strait of Gibraltar traps as a reference and providing a vision from ancient times to the present, scientific activities on this fishing gear are reviewed in an attempt to explain the reasons behind the crisis of the catches in this fishery, which began at the beginning of the 1960s and which has been extended until recent times. In order to do so and based on a recent publication on the issue, the Bay of Biscay fishery is presented as a fishery with a long tradition on which numerous scientific studies have been carried out and whose data are of great importance in the ABFT assessment group of SCRS (ICCAT's scientific committee). Traditionally, the catches of this fishery have been made up of juvenile specimens (<40 kg) making up more than 97% in number of fishes according to a 62-year series studied (1949-2010). From an analysis of the population, it has been shown that the impact of massive fishing of juveniles in this fishery between 1949 and 1962, together with that of juveniles in Morocco (the Atlantic part) possibly caused the decline of the traditional traps fishery of spawners in the Strait of Gibraltar and the collapse of the spawner fisheries in the north of Europe from the 1960s. This situation continued until 2007, the year from which a Pluri-Annual Recovery Plan (PARP) was adopted by ICCAT for the eastern stock. Since the PARP was implemented, juvenile catches have disappeared from almost all the fisheries, a scenario that coincides with a considerable recovery of the spawning stock biomass in the easter Atlantic and Mediterranean, according to the results of the latest SCRS assessments. Keywords Atlantic Bluefin Tuna Á Traps Á Strait of Gibraltar Á Bay of Biscay Á Juveniles Fishing xi Chapter 1
Scientific advice on the concept of surplus, as defined by the UNCLOS, was provided for three typ... more Scientific advice on the concept of surplus, as defined by the UNCLOS, was provided for three types of Sustainable Fisheries Partnership Agreements (SFPAs): i) Mixed SFPAs in West Africa, ii) Tuna SFPAs and iii) SFPA with Greenland. For Mixed SFPAs in West Africa, methods for surplus computation were defined, including alternatives for cases of data limited stocks. These methods may use as input five parameters that could be obtained from those recent stocks assessments that are representative of the current stock status. Surplus estimates would need to be regularly updated (ideally, yearly), according to every new stock assessments and following the enforcement of a management plan (or, by default, according to a transition scheme towards reaching Fmsy in 2020). In the case of West African transboundary stocks, a theoretical share of the surplus could be calculated using a standard rule based on historical catches within EEZs. The Surplus concept is not applicable for Tuna SFPAs, d...
Parasitology International, 2021
Parasitic castration is a phenomenon where the parasite blocks or reduces the host reproductive o... more Parasitic castration is a phenomenon where the parasite blocks or reduces the host reproductive output. This study explored the impact of Tetracotyle wayanadensis infection on the reproductive performance of the freshwater fish Aplocheilus lineatus. Heavily infected A. lineatus showed slow and sluggish movements with reduced food intake and feeding activities. Histopathological observations of the ovary revealed severe necrosis and degeneration of previtellogenic and vitellogenic oocytes and follicular atresia. The oogonial nests were absent; chromatin nucleolar oocytes irregularly shaped and vacuolated. Perinucleolar oocytes have a vacuolated appearance with the hypertrophied highly columnar follicular cells invading them. Vitellogenic oocytes had a shrunken appearance with folded zona radiata; yolk globules broken down into smaller granules together with vacuolar degeneration of the ooplasm. The hypertrophied highly columnar follicular cells invaded the early vitellogenic oocytes to phagocytize the degenerating material. Zona radiata was found broken and liquefaction of yolk globules was evident with advancement in follicular atresia. Seasonal variation of parasitic infection has also been studied. Metacercaria infecting the vital organs showed seasonal variation with the highest values for prevalence and abundance during monsoon and mean intensity during winter. The lowest values for these descriptors were documented during the post-monsoon period.
In ordinary catch at age models, natural mortality conditions and determines the catchabilities a... more In ordinary catch at age models, natural mortality conditions and determines the catchabilities at age obtained for the surveys which tune the assessments. For the same reason, inferring the Natural mortality of a fish stock from surveys' estimates, require some assumption of the survey catchabilities at age. The anchovy fishery in the Bay of Biscay has been closed since 2005 up to 2010, due to low biomass levels. In the mean time, and since 1989, the population has been directly monitored by two independent surveys, acoustic and egg (DEPM) surveys, which supplied the basic information for the assessment of this stock carried out by ICES. The closure of the fishery supposes a major contrast on total mortality levels affecting the population in comparison with the former period of exploitation, suitable to get estimates of Natural and Fishing mortalities, under the assumption of no major changes in M occurring between both periods. Log linear models and a seasonal integrate catch at age analysis were tuned to the fishery and two series of surveys under the assumption of constant catchabilities across ages for the two surveys' population estimates. An analysis of the period 1987-2009, searching for a single and constant natural mortality at age, results in minimum residual SSQ for an M around 0.8. But a better result is obtained when a pattern of increasing natural mortality at age is allowed, a possibility suggested since a long time for this type of short living species.
Se ha medido el diámetro del núcleo de otolitos de anchoa, Engraulis encrasicolus (Linnaeus, 1758... more Se ha medido el diámetro del núcleo de otolitos de anchoa, Engraulis encrasicolus (Linnaeus, 1758), recogidos en el Cantábrico oriental, en el occidental y en Galicia durante 1995 y 1998 para comprobar si existían diferencias en su longitud y, si era así, si estas diferencias eran características de los grupos de población de la especie. Los resultados muestran diferencias significativas entre las tres regiones y, aunque deben considerarse solamente como preliminares, parecen indicar que estas diferencias pueden ser propias de los grupos de población de anchoa descritos en las regiones estudiadas.