... of Cape hakes (Macpherson et aI., 1991) and other demersal species (Macpherson and Gordoa, 19... more ... of Cape hakes (Macpherson et aI., 1991) and other demersal species (Macpherson and Gordoa, 1992). ... paradoxus), the most valuable demersal resource in the region since 1965 (De Villiers, 1985 ... and resulted in a redistribution of South African fishing effort and an increase in ...
This study analyses the distribution and diet overlap of the early stages of sardine and hake off... more This study analyses the distribution and diet overlap of the early stages of sardine and hake off the Catalan coast during the autumn spawning period. Data on horizontal and vertical distributions of eggs and larvae, the larval size structure in the overlapping zones ...
This paper describes the suitability of a closed recirculation system to study the development of... more This paper describes the suitability of a closed recirculation system to study the development of fish larvae in a strictly controlled environment, where only feeding was varied (fed, starved, delayed and late fast treatments). The system served both as an incubator and hatchery. The time variation of physical and chemical parameters together with survival and growth of reared sea bass larvae (Dicentrarchus labrax) were studied over the first month of life. The recirculation design allowed for the maintenance of levels of ammonia, nitrite and nitrate below those cited as responsible for mortality or decreased feeding ability in other marine fish larvae. Almost no larval mortality occurred in the fed larvae from day 9 after hatching. The starved group of larvae showed a sharp decline in survival after 16 days of food deprivation. Larvae for which feeding was delayed until day 13 ceased dying 4 days after food was supplied. Fast feeding on days 24 and 25 had no effect on larval survival. Growth in length was similar during the first 2 weeks of larval life regardless of feeding treatment. Two days of late fast had no effect on larval growth. Growth patterns of fed larvae in this study were similar to those reported for larvae reared in flow through systems. We believe that survival and growth of the reared larvae was a direct function of diet, and that the type of rearing system did not adversely affect these parameters. The rearing design and the results obtained suggest that future nutritional studies of field-collected larvae will benefit from this kind of rearing experiment.
... Sci. 8: 173-181 1989 EARLY LIFE HISTORY AND SPAWNING OF GENYPTERUS CAPENSIS (SMITH, 1849) IN ... more ... Sci. 8: 173-181 1989 EARLY LIFE HISTORY AND SPAWNING OF GENYPTERUS CAPENSIS (SMITH, 1849) IN THE SOUTHERN BENGUELA SYSTEM MP. ... Aan die Weskus vind kuitskiet net plaas in daardie maande wanneer opwelling minder hewig is (Junie-Desember). 173 ...
Scientia Marina és successora de la revista Investigación Pesquera, una revista de ciències marin... more Scientia Marina és successora de la revista Investigación Pesquera, una revista de ciències marines publicada des de 1955 per l'Institut de Ciències del Mar de Barcelona (CSIC). Des dels inicis, la revista va donar cobertura a articles dels diversos camps de les ciències marines, tot i que en els primers anys hi dominaven els treballs sobre temes pesquers o espècies d'interès comercial, d'acord amb la primera denominació de la revista. Ben aviat, però, els articles publicats van abraçar molts altres àmbits de la recerca marina. Aquest va ser un dels motius pels quals l'any 1989 es decidí canviar el nom de la revista per adaptar-Primeres Jornades Catalanes de Revistes Científiques
Canadian Journal of Fisheries and Aquatic Sciences, 2014
The distributions of micronekton layers in the Balearic Sea (western Mediterranean) were investig... more The distributions of micronekton layers in the Balearic Sea (western Mediterranean) were investigated by acoustic methods. Two multidisciplinary surveys were carried out in late autumn 2009 and summer 2010, recording acoustic, biological, and hydrographic data. We described acoustic layers, migratory behavior, sampled species, and water masses processes. Acoustic modeling of gas-bearing organisms was employed to explain differences between acoustic estimates and sampled abundances. The influence of environmental variables on the vertical distribution and migration pattern of these organisms was analyzed. The thermocline depth was related to the preferred depth for migrating myctophids, while nonmigrant species dwelled in the oxygen minimum zone of the water column both in late autumn and summer periods.
Argentinean hake, Merluccius hubbsi, is one of the most important fishery resources of the South-... more Argentinean hake, Merluccius hubbsi, is one of the most important fishery resources of the South-western Atlantic Ocean, but its spawning biomass decreased in the last fifteen years, mainly due to the increased fishing pressure. It is widely accepted that to understand recruitment variability is necessary to study the factors that determine survival of early stages of development. Nutritional condition indexes have been widely used to determine starvation in wild larvae. In the present investigation, condition of M. hubbsi larvae was estimated employing field collected material by means of RNA/DNA index. This is the first attempt to use this index in this species. The change in the RNA/DNA index showed a clear ontogenetic pattern: increasing from preflexion to postflexion stages, showing an apparent decrease at the end of postflexion stage and a conspicuous increase once transformation stage was achieved. This pattern could be indicating that the transition between postflexion and transformation stages might represent a critical phase along larval development. RNA/DNA index also showed significant differences between areas from the spawning grounds characterized by different chlorophyll a concentration and abundance of potential prey. The study of nutritional condition represents a useful tool for identifying favorable nursery areas, providing valuable information for a comprehensive management of a population subject to overfishing.
The growth and age of the lanternfish Ceratoscopelus maderensis from the western Mediterranean Se... more The growth and age of the lanternfish Ceratoscopelus maderensis from the western Mediterranean Sea (December 2009) was estimated throughout its entire lifespan, using otoliths (sagitta) of 59 individuals, from of 3.5 mm (larva) to of 64 mm (mature adult) standard length (SL). Sagittal otoliths were analyzed by means of light microscope in larvae. The examination of several sagitta from transforming and juvenile-adult stages was also accomplished by means of scanning electron microscopy (SEM) to determine otolith microstructure in those zones that were under the light microscopic resolution threshold. Serial photographs of each sagitta were mounted to count increment rings over the entire development of the specimens, and subsequently, estimate individual ages, under the assumption that the microincrements are formed by daily deposition (proven in other studies on myctophids). Maximum radius followed a significantly positive linear regression with body length. Three characteristic zo...
In the NW Mediterranean Sea, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) ar... more In the NW Mediterranean Sea, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) are the most important small pelagic fish in terms of biomass and commercial interest. Round sardinella (Sardinella aurita) and Sprat (Sprattus sprattus) are also present in this region. This paper provides a general insight into the ecology of these species through a revision of the information available in an environmental context and in relation to exploitation features. Spawning habitats of the two main species, anchovy and sardine, are clearly differentiated based on water mass characteristics reducing the overlapping between their early developmental stages. Larval distribution is also related to major productivity mechanisms of the respective spawning seasons. In spite of the different environmental regimes in which larvae of these species develop, growth rates are fairly similar. Trophic modeling highlights the important ecological role of small pelagic fish in North Western Mediterranean ecosystems. This review points out the gaps in knowledge necessary to understand the dynamics of small pelagic fish in the region and to progress towards a precautionary and adaptive management.
The present paper reports on temporalmesoscale (weeks) changes in physical and biological couplin... more The present paper reports on temporalmesoscale (weeks) changes in physical and biological coupling in the cross-frontal area off the coast of Catalonia in Spain (NW Mediterranean) during the spring transition period. The effect of short-term physical variability on the spatio-temporal heterogeneity of phytoplankton biomass and in the area of overlap of the larvae of fish species dwelling on the shelf
Mesopelagic fishes experience an extreme body transformation from larvae to adults. The identific... more Mesopelagic fishes experience an extreme body transformation from larvae to adults. The identification of the larval stages of fishes from the two orders Myctophiformes and Stomiiformes is currently based on the comparison of morphological, pigmentary and meristic characteristics of different developmental stages. However, no molecular evidence to confirm the identity of the larvae of these mesopelagic species is available so far. Since DNA barcoding emerged as an accurate procedure for species discrimination and larval identification, we have used the cytochrome c oxidase 1 or the mitochondrial 12S ribosomal DNA regions to identify larvae and adults of the most frequent and abundant species of myctophiforms (family Myctophidae) and stomiiforms (families Gonostomatidae, Sternoptychidae and Phosichthyidae) from the Mediterranean Sea. The comparisons of sequences from larval and adult stages corroborated the value of the morphological characters that were used for taxonomic classification. The combination of the sequences obtained in this study and those of related species from GenBank was used to discuss the consistency of monophyletic clades for different genera. Pairwise nucleotide distances were notably higher inter-than intraspecifically, and were useful to discern between congeners such as Cyclothone braueri and C. pygmaea, Hygophum benoiti and H. hygomii, Lampanyctus crocodilus and L. pusillus, and Notoscopelus bolini and N. elongatus.
Assay protocols for RNA and DNA in crude plankton extracts using the fluorochrome SYBR Green II a... more Assay protocols for RNA and DNA in crude plankton extracts using the fluorochrome SYBR Green II are developed here. The method is based on the fluorescence in 3 aliquots: the first measures RNA after DNA digestion; the second measures DNA after RNA digestion; and the third measures residual fluorescence after digestion of both DNA and RNA. This residual fluorescence measurement is critical for accurate calculations of the nucleic acids. Optimisation of the assay conditions are described: fluorochrome concentration, buffer composition, fluorescence stability, temperature and duration of nuclease incubation. In the optimised procedure, the assays are performed in 5 mM Tris buffer (containing 0.9 mM CaCl 2 •2H 2 O and 0.9 mM MgCl 2 •6H 2 O, pH 8.0); DNase and RNase incubations are conducted at 37ºC for 20 min; the fluorochrome is added to all assays at a final concentration of 3.5x10-4 and readings are done within the 10-60 min period following the SYBR Green II addition. The study evidenced the importance of the residual fluorescence after nuclease digestion, which is especially taken into account in the calculation of the nucleic acid concentrations. Finally, the variability of the fluorescent response to different RNA and DNA standards is examined; from the performed tests, calculations are based on rRNA from calf liver and DNA from calf thymus standards. The accompanying paper (Berdalet et al., 2005) describes the development of the extraction protocol, as well as the application of both protocols in measuring RNA/DNA ratios in natural plankton samples, and a comparison with ethidium bromide based methods.
The larval growth and development of the European hake, Merluccius merluccius, was studied from f... more The larval growth and development of the European hake, Merluccius merluccius, was studied from field larvae. Larvae were collected in the northwestern Mediterranean on three cruises carried out during the peak spawning months (November 1998, September 1999 and November 1999). Like other species of the genus, these larvae are characterised by a well-developed anterior part of the body, head and trunk region. Nevertheless, yolk sac larvae are much more slender than larvae at notochordal flexion stages. In the present study we analysed the allometric relationships between several body measurements and body length. This is the first attempt to infer larval growth of Merluccius merluccius by means of sagittal otolith analysis. Our results show the change in the otolith shape from a lenticular otolith in early larvae to an almond-shaped otolith in larger larvae. Otolith diameter showed a power relation with larval size, with no significant differences between seasons. In spite of the sea surface temperature differences between the three periods of larval collection, the early growth estimates showed no significant differences. This was explained by the similarity in the temperature at the depths at which the larvae are located. Absolute growth rates in length were estimated by relating daily growth increments in otoliths and larval size (standard length). When using the whole larval size range the values obtained were similar to those found for other Merluccius species. Nevertheless, the present data evidenced that growth for larvae younger than 12 days is very low, showing a significant increase thereafter. This indicates that length is probably not the best parameter for describing the growth of hake larvae in the first days of life, as allometric analysis suggested.
... of Cape hakes (Macpherson et aI., 1991) and other demersal species (Macpherson and Gordoa, 19... more ... of Cape hakes (Macpherson et aI., 1991) and other demersal species (Macpherson and Gordoa, 1992). ... paradoxus), the most valuable demersal resource in the region since 1965 (De Villiers, 1985 ... and resulted in a redistribution of South African fishing effort and an increase in ...
This study analyses the distribution and diet overlap of the early stages of sardine and hake off... more This study analyses the distribution and diet overlap of the early stages of sardine and hake off the Catalan coast during the autumn spawning period. Data on horizontal and vertical distributions of eggs and larvae, the larval size structure in the overlapping zones ...
This paper describes the suitability of a closed recirculation system to study the development of... more This paper describes the suitability of a closed recirculation system to study the development of fish larvae in a strictly controlled environment, where only feeding was varied (fed, starved, delayed and late fast treatments). The system served both as an incubator and hatchery. The time variation of physical and chemical parameters together with survival and growth of reared sea bass larvae (Dicentrarchus labrax) were studied over the first month of life. The recirculation design allowed for the maintenance of levels of ammonia, nitrite and nitrate below those cited as responsible for mortality or decreased feeding ability in other marine fish larvae. Almost no larval mortality occurred in the fed larvae from day 9 after hatching. The starved group of larvae showed a sharp decline in survival after 16 days of food deprivation. Larvae for which feeding was delayed until day 13 ceased dying 4 days after food was supplied. Fast feeding on days 24 and 25 had no effect on larval survival. Growth in length was similar during the first 2 weeks of larval life regardless of feeding treatment. Two days of late fast had no effect on larval growth. Growth patterns of fed larvae in this study were similar to those reported for larvae reared in flow through systems. We believe that survival and growth of the reared larvae was a direct function of diet, and that the type of rearing system did not adversely affect these parameters. The rearing design and the results obtained suggest that future nutritional studies of field-collected larvae will benefit from this kind of rearing experiment.
... Sci. 8: 173-181 1989 EARLY LIFE HISTORY AND SPAWNING OF GENYPTERUS CAPENSIS (SMITH, 1849) IN ... more ... Sci. 8: 173-181 1989 EARLY LIFE HISTORY AND SPAWNING OF GENYPTERUS CAPENSIS (SMITH, 1849) IN THE SOUTHERN BENGUELA SYSTEM MP. ... Aan die Weskus vind kuitskiet net plaas in daardie maande wanneer opwelling minder hewig is (Junie-Desember). 173 ...
Scientia Marina és successora de la revista Investigación Pesquera, una revista de ciències marin... more Scientia Marina és successora de la revista Investigación Pesquera, una revista de ciències marines publicada des de 1955 per l'Institut de Ciències del Mar de Barcelona (CSIC). Des dels inicis, la revista va donar cobertura a articles dels diversos camps de les ciències marines, tot i que en els primers anys hi dominaven els treballs sobre temes pesquers o espècies d'interès comercial, d'acord amb la primera denominació de la revista. Ben aviat, però, els articles publicats van abraçar molts altres àmbits de la recerca marina. Aquest va ser un dels motius pels quals l'any 1989 es decidí canviar el nom de la revista per adaptar-Primeres Jornades Catalanes de Revistes Científiques
Canadian Journal of Fisheries and Aquatic Sciences, 2014
The distributions of micronekton layers in the Balearic Sea (western Mediterranean) were investig... more The distributions of micronekton layers in the Balearic Sea (western Mediterranean) were investigated by acoustic methods. Two multidisciplinary surveys were carried out in late autumn 2009 and summer 2010, recording acoustic, biological, and hydrographic data. We described acoustic layers, migratory behavior, sampled species, and water masses processes. Acoustic modeling of gas-bearing organisms was employed to explain differences between acoustic estimates and sampled abundances. The influence of environmental variables on the vertical distribution and migration pattern of these organisms was analyzed. The thermocline depth was related to the preferred depth for migrating myctophids, while nonmigrant species dwelled in the oxygen minimum zone of the water column both in late autumn and summer periods.
Argentinean hake, Merluccius hubbsi, is one of the most important fishery resources of the South-... more Argentinean hake, Merluccius hubbsi, is one of the most important fishery resources of the South-western Atlantic Ocean, but its spawning biomass decreased in the last fifteen years, mainly due to the increased fishing pressure. It is widely accepted that to understand recruitment variability is necessary to study the factors that determine survival of early stages of development. Nutritional condition indexes have been widely used to determine starvation in wild larvae. In the present investigation, condition of M. hubbsi larvae was estimated employing field collected material by means of RNA/DNA index. This is the first attempt to use this index in this species. The change in the RNA/DNA index showed a clear ontogenetic pattern: increasing from preflexion to postflexion stages, showing an apparent decrease at the end of postflexion stage and a conspicuous increase once transformation stage was achieved. This pattern could be indicating that the transition between postflexion and transformation stages might represent a critical phase along larval development. RNA/DNA index also showed significant differences between areas from the spawning grounds characterized by different chlorophyll a concentration and abundance of potential prey. The study of nutritional condition represents a useful tool for identifying favorable nursery areas, providing valuable information for a comprehensive management of a population subject to overfishing.
The growth and age of the lanternfish Ceratoscopelus maderensis from the western Mediterranean Se... more The growth and age of the lanternfish Ceratoscopelus maderensis from the western Mediterranean Sea (December 2009) was estimated throughout its entire lifespan, using otoliths (sagitta) of 59 individuals, from of 3.5 mm (larva) to of 64 mm (mature adult) standard length (SL). Sagittal otoliths were analyzed by means of light microscope in larvae. The examination of several sagitta from transforming and juvenile-adult stages was also accomplished by means of scanning electron microscopy (SEM) to determine otolith microstructure in those zones that were under the light microscopic resolution threshold. Serial photographs of each sagitta were mounted to count increment rings over the entire development of the specimens, and subsequently, estimate individual ages, under the assumption that the microincrements are formed by daily deposition (proven in other studies on myctophids). Maximum radius followed a significantly positive linear regression with body length. Three characteristic zo...
In the NW Mediterranean Sea, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) ar... more In the NW Mediterranean Sea, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) are the most important small pelagic fish in terms of biomass and commercial interest. Round sardinella (Sardinella aurita) and Sprat (Sprattus sprattus) are also present in this region. This paper provides a general insight into the ecology of these species through a revision of the information available in an environmental context and in relation to exploitation features. Spawning habitats of the two main species, anchovy and sardine, are clearly differentiated based on water mass characteristics reducing the overlapping between their early developmental stages. Larval distribution is also related to major productivity mechanisms of the respective spawning seasons. In spite of the different environmental regimes in which larvae of these species develop, growth rates are fairly similar. Trophic modeling highlights the important ecological role of small pelagic fish in North Western Mediterranean ecosystems. This review points out the gaps in knowledge necessary to understand the dynamics of small pelagic fish in the region and to progress towards a precautionary and adaptive management.
The present paper reports on temporalmesoscale (weeks) changes in physical and biological couplin... more The present paper reports on temporalmesoscale (weeks) changes in physical and biological coupling in the cross-frontal area off the coast of Catalonia in Spain (NW Mediterranean) during the spring transition period. The effect of short-term physical variability on the spatio-temporal heterogeneity of phytoplankton biomass and in the area of overlap of the larvae of fish species dwelling on the shelf
Mesopelagic fishes experience an extreme body transformation from larvae to adults. The identific... more Mesopelagic fishes experience an extreme body transformation from larvae to adults. The identification of the larval stages of fishes from the two orders Myctophiformes and Stomiiformes is currently based on the comparison of morphological, pigmentary and meristic characteristics of different developmental stages. However, no molecular evidence to confirm the identity of the larvae of these mesopelagic species is available so far. Since DNA barcoding emerged as an accurate procedure for species discrimination and larval identification, we have used the cytochrome c oxidase 1 or the mitochondrial 12S ribosomal DNA regions to identify larvae and adults of the most frequent and abundant species of myctophiforms (family Myctophidae) and stomiiforms (families Gonostomatidae, Sternoptychidae and Phosichthyidae) from the Mediterranean Sea. The comparisons of sequences from larval and adult stages corroborated the value of the morphological characters that were used for taxonomic classification. The combination of the sequences obtained in this study and those of related species from GenBank was used to discuss the consistency of monophyletic clades for different genera. Pairwise nucleotide distances were notably higher inter-than intraspecifically, and were useful to discern between congeners such as Cyclothone braueri and C. pygmaea, Hygophum benoiti and H. hygomii, Lampanyctus crocodilus and L. pusillus, and Notoscopelus bolini and N. elongatus.
Assay protocols for RNA and DNA in crude plankton extracts using the fluorochrome SYBR Green II a... more Assay protocols for RNA and DNA in crude plankton extracts using the fluorochrome SYBR Green II are developed here. The method is based on the fluorescence in 3 aliquots: the first measures RNA after DNA digestion; the second measures DNA after RNA digestion; and the third measures residual fluorescence after digestion of both DNA and RNA. This residual fluorescence measurement is critical for accurate calculations of the nucleic acids. Optimisation of the assay conditions are described: fluorochrome concentration, buffer composition, fluorescence stability, temperature and duration of nuclease incubation. In the optimised procedure, the assays are performed in 5 mM Tris buffer (containing 0.9 mM CaCl 2 •2H 2 O and 0.9 mM MgCl 2 •6H 2 O, pH 8.0); DNase and RNase incubations are conducted at 37ºC for 20 min; the fluorochrome is added to all assays at a final concentration of 3.5x10-4 and readings are done within the 10-60 min period following the SYBR Green II addition. The study evidenced the importance of the residual fluorescence after nuclease digestion, which is especially taken into account in the calculation of the nucleic acid concentrations. Finally, the variability of the fluorescent response to different RNA and DNA standards is examined; from the performed tests, calculations are based on rRNA from calf liver and DNA from calf thymus standards. The accompanying paper (Berdalet et al., 2005) describes the development of the extraction protocol, as well as the application of both protocols in measuring RNA/DNA ratios in natural plankton samples, and a comparison with ethidium bromide based methods.
The larval growth and development of the European hake, Merluccius merluccius, was studied from f... more The larval growth and development of the European hake, Merluccius merluccius, was studied from field larvae. Larvae were collected in the northwestern Mediterranean on three cruises carried out during the peak spawning months (November 1998, September 1999 and November 1999). Like other species of the genus, these larvae are characterised by a well-developed anterior part of the body, head and trunk region. Nevertheless, yolk sac larvae are much more slender than larvae at notochordal flexion stages. In the present study we analysed the allometric relationships between several body measurements and body length. This is the first attempt to infer larval growth of Merluccius merluccius by means of sagittal otolith analysis. Our results show the change in the otolith shape from a lenticular otolith in early larvae to an almond-shaped otolith in larger larvae. Otolith diameter showed a power relation with larval size, with no significant differences between seasons. In spite of the sea surface temperature differences between the three periods of larval collection, the early growth estimates showed no significant differences. This was explained by the similarity in the temperature at the depths at which the larvae are located. Absolute growth rates in length were estimated by relating daily growth increments in otoliths and larval size (standard length). When using the whole larval size range the values obtained were similar to those found for other Merluccius species. Nevertheless, the present data evidenced that growth for larvae younger than 12 days is very low, showing a significant increase thereafter. This indicates that length is probably not the best parameter for describing the growth of hake larvae in the first days of life, as allometric analysis suggested.
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Papers by M. Olivar