Developments in Aquaculture and Fisheries Science, 2006
Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scall... more Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scallop) and Zygochlamys patagonica (Patagonic scallop), their fisheries, and experimental results that have significance in the future development of aquaculture. The fisheries supported by these two species are radically different from each other. The Tehuelche scallop is the target of small inshore fisheries in the gulfs of northern Patagonia, and involves dredging and commercial diving. In spite of the small volumes landed, these fisheries are of considerable significance for the local economies. The Patagonic scallop fishery is an industrial operation conducted by three or four factory trawlers that process the catch at sea. Catches in the order of 50,000 tons yr -1 now rank this species among the most important scallop fisheries in the World. The Tehuelche scallop is a simultaneous hermaphrodite and is iteroparous. The Tehuelche scallop may do quick and brief swimming movements as an escape response to the predators or other disturbances.
ABSTRACT The radular morphology of Zidona dufresnei was studied by optical and scanning electron ... more ABSTRACT The radular morphology of Zidona dufresnei was studied by optical and scanning electron microscopy. We analysed the variability among and within three populations distributed along the southwestern Atlantic Ocean coast, considering the hypothesis that the isolation among populations favours adaptive phenotypic variation, which is also expressed at the radular level. Populations selected for this study differ in their maximum individual size, growth rate, size and age at maturity, and fecundity. This study provides the first analysis of the interpopulational variability of the radula of Zidona dufresnei and the first description of its morphology. Zidonia dufresnei exhibited a rachiglossate radulae composed of rows of tricuspid teeth (radular formula: 0+R+0). No differences in tooth shape among populations and sexes were observed. However, significant interpopulational differences in the height of the rachidian cusp and total length of the radula were detected. Specimens from San Antonio Bay showed the lowest values for all radular variables. Positive significant relationships between total shell length and the height of the rachidian cusp and total length of the radula were found, while the number of rows remained relatively constant regardless of size. The larger morphotypes had a longer radula because of an increase in the height of the rachidian cusp. No sexual dimorphism was observed in any morphometric variables of the radula. The results suggest that populations distributed along the Argentine Sea are homogeneous for radular morphology, despite the differences in life history traits, which may be linked to a similarity in feeding habits across populations.
The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stre... more The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stresses increase, habitat amelioration by ecosystem engineers becomes more relevant. Moreover, the individual-and population-level traits of ecosystem engineers can affect their ability to reduce environmental stress. On the Patagonian shores of Argentina (SW Atlantic, 41°S), the intertidal community is exposed to harsh conditions. We predicted that in this severe environment, variation in the above-ground structure of the smooth cordgrass Spartina alterniflora should buffer the physical stress on the substrate through shading and reduction of wind and water flow energy, ultimately affecting the sediment properties and microphytobenthic biomass. To test this hypothesis, we experimentally manipulated cordgrass density at the edge and inner marsh of a S. alterniflora meadow during both summer and winter. In summer, evaporation and temperature were higher in clipped plots, while in winter, evaporation varied across densities and location treatments, with higher sediment water content in the inner marsh. No effect of S. alterniflora density or location were observed on sediment organic matter or chl a concentration, and mean sediment grain size was always smaller inside the marsh. In summer, extracellular polymeric substance (EPS) content was higher in clipped plots inside the marsh, however this did not differ from the other density treatments at this location. Overall, shading had weak effects on sediment properties and microphytobenthic biomass, and most observed differences were attributable to grain size. We speculate that the harsh conditions of this system overwhelm the ecosystem engineering effects of S. alterniflora, probably because of its relatively small aboveground biomass.
The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stre... more The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stresses increase, habitat amelioration by ecosystem engineers becomes more relevant. Moreover, the individual-and population-level traits of ecosystem engineers can affect their ability to reduce environmental stress. On the Patagonian shores of Argentina (SW Atlantic, 41°S), the intertidal community is exposed to harsh conditions. We predicted that in this severe environment, variation in the above-ground structure of the smooth cordgrass Spartina alterniflora should buffer the physical stress on the substrate through shading and reduction of wind and water flow energy, ultimately affecting the sediment properties and microphytobenthic biomass. To test this hypothesis, we experimentally manipulated cordgrass density at the edge and inner marsh of a S. alterniflora meadow during both summer and winter. In summer, evaporation and temperature were higher in clipped plots, while in winter, evaporation varied across densities and location treatments, with higher sediment water content in the inner marsh. No effect of S. alterniflora density or location were observed on sediment organic matter or chl a concentration, and mean sediment grain size was always smaller inside the marsh. In summer, extracellular polymeric substance (EPS) content was higher in clipped plots inside the marsh, however this did not differ from the other density treatments at this location. Overall, shading had weak effects on sediment properties and microphytobenthic biomass, and most observed differences were attributable to grain size. We speculate that the harsh conditions of this system overwhelm the ecosystem engineering effects of S. alterniflora, probably because of its relatively small aboveground biomass.
Journal of the Marine Biological Association of the United Kingdom, Apr 21, 2015
Growth rates and size-age at maturity are life history traits that combine in different ways to a... more Growth rates and size-age at maturity are life history traits that combine in different ways to achieve maximal fitness. The marine scavenger Buccinanops globulosus was used as a model to explore the variation on female size-age at maturity and reproductive effort among three populations characterized by different growth rates (slow, moderate and rapid). This species constitutes the target of an artisanal fishery in North Patagonia. Here, a suite of different estimators of size-age at maturity derived from gonad histological analysis and the study of females carrying egg capsules were obtained. Data were modelled using a logistic function and the maturity patterns were compared among populations. We found that female size and age at maturity were variable and site-specific. The fastest-growing population showed the lowest reproductive effort. Slow and rapid-growing females mature at different sizes but at the same age whereas moderate-growing females mature both at a different size and age (intermediate size and at earlier age). Thus, results obtained here are difficult to reconcile with a single reaction norm for a single genotype in the studied populations. Growth rate variation is not enough to explain the patterns described here. The information provided could be used for the establishment of fishery management actions, such as minimum landing size.
A cohort of juveniles Aequipecten tehuelchus was obtained on collectors placed in the San Matı́as... more A cohort of juveniles Aequipecten tehuelchus was obtained on collectors placed in the San Matı́as Gulf in the 1997–1998 reproductive season, and was cultivated in circular lantern nets or screened plastic trays. An additional trial using the “ear hanging” method was ultimately terminated due to formation of excessive biofouling on the shells, although some growth and survival data were obtained
ABSTRACT Feeding decisions under predation risk can be a key in the life of scavenger organisms, ... more ABSTRACT Feeding decisions under predation risk can be a key in the life of scavenger organisms, and tuned recognition of predation alarm cues and flexibility in the response are fundamental. The effect of injured conspecifics on the response behavior of the whelk Buccinanops globulosum to feeding opportunities was experimentally evaluated in a Patagonian Bay (40°45′S, 64°56′W, Argentina) in September 2010. The effect of sex, size, body condition, or starvation on anti-predatory behavior was assessed. The number of B. globulosum feeding on carrion was reduced by half when damaged conspecifics were present. Smaller, lighter, and starved individuals responded less to the presence of damaged conspecifics. These results indicate that, under natural conditions, feeding avoidance after detecting damaged conspecifics is a common and important anti-predatory strategy of B. globulosum and show that morphology and starvation are significant factors in the context of the trade-off between feeding and avoiding predation risk.
Journal of the World Aquaculture Society, Mar 1, 1995
Studies on larval settlement and growth of the commercial scallop Aeguipcten tehuelchus were carr... more Studies on larval settlement and growth of the commercial scallop Aeguipcten tehuelchus were carried out over a 2-yr period in San Matias Gulf, Argentina. Gonadal index was used to indicate spawning and spat collectors were deployed when spawning began. Artificial spat collectors (monofilament bags filled with thin shrub branches) were placed at a depth of 25 m in two areas of the Gulf during two seasons (1989-1990 and 1991-1992). Maximum settlement occurred by mid-February during the first season and by midJanuary in the second season. Larger numbers of spat were found in collectors placed near the sea bottom. After settlement, spat were removed and placed in cages for growout. Scallops reached the average commercial size (60 mm shell height) 16 mo later. Mortality rate during the entire period was 10%.
Experiments on fertilization (self-fertilization and cross-mating), embryonic density, larval fee... more Experiments on fertilization (self-fertilization and cross-mating), embryonic density, larval feeding, survival and larval settlement on natural substrata were carried out in order to identify some of the basic requirements of the early life history of Aequipecten tehuelchus reared under hatchery conditions.In self-fertilization, the main developmental stages were represented by the initial stages, mainly nonfertilized oocytes and embryos going through early
Abstract Time-series of fishing position, landings, satellite-derived sea-surface temperature and... more Abstract Time-series of fishing position, landings, satellite-derived sea-surface temperature and chlorophyll a concentrations were used to relate the spatial–temporal distribution of the Argentine hake Merluccius hubbsi with seasonal oceanographic processes in San Matías Gulf. Also, the seasonal effect of fishing on the hake population structure was analysed. During summer the fleet was concentrated over the area of the frontal system, obtaining the best catch-per-unit-effort (CPUE) of hake in relatively deep waters. In autumn, the dispersion of the fleet due to a reduction in CPUE coincided with the dissipation of the front, suggesting that the distribution and shoaling of the Argentine hake is associated with seasonal thermal structures. In spring, the thermal structure of the waters and the chlorophyll a blooms seem to modulate the timing of spawning of hake, which occurs mainly in October–November. In addition, the fleet captured a higher proportion of females in the gonadal recovery stage during warm months (November–April). While winter catches (May–October) consisted mainly of males, the intense summer fishing may result in a high impact on the female population. This information is relevant to design of spatial management tools intended to provide biological sustainability to the hake fishery.
The relationship between the pinnotherid crab Tumidotheres maculatus and its scallop host Aequipe... more The relationship between the pinnotherid crab Tumidotheres maculatus and its scallop host Aequipecten tehuelchus was studied over an annual cycle from November 1999 to November 2000, on a scallop bank in the NW sector of the San Matías Gulf, Argentina. T. maculatus was found within the mantle cavity of the scallop. The female crabs were larger than the males, and the proportion of females was always larger than that of males, in some months reaching 100%. Carapace lengths of the crabs varied from 1 to 16 mm. Most infested scallops contained a single crab. Infestation with one gravid female excluded the presence of other females. The level of infestation (prevalence) varied between 14.3 and 50.0%. No relationship was observed between the prevalence of the crabs and depths occupied by the scallops. As scallops grew, the weight gain of non-infested scallops was greater than those infested (ANCOVA; P < 0.01). Indices of meat yield (muscle, gonad) of individuals not infested with T. maculatus were greater than indices of infested scallops (ANOVA; P < 0.05), indicating a parasitic relationship. The effect of crab infestation on the scallop industry is discussed.
The fishery for the swimming crab Ovalipes trimaculatus in the southwestern Atlantic started in 2... more The fishery for the swimming crab Ovalipes trimaculatus in the southwestern Atlantic started in 2007, with an average catch of 64.36 t⋅y −1 during the period between 2008 and 2013. The fishery is under an open access regime and market demand exceeds the catch which raises concern about its future. It is also data-poor, which prevents researchers from using traditional assessment methods. The factors that limit the fishing effort were identified by analyzing the fishing operation, the decision making process of the fishers and CPUE. Changes in catch composition through space and time, and the distribution of the population along a depth gradient were also studied. Wind, recent yield and the price of crab were perceived by skippers as relevant factors when deciding to go fishing, but there was no relationship between these variables and monthly fishing effort. However, daily fishing effort depended on wind conditions. During the studied period (2008-2013) the CPUE of 2009 was the only one lower than the CPUE of 2008, and the number of fishing grounds as well as their respective area have not increased. The species depth distribution reaches 60 m deep, which is much deeper than the depths divers can reach (about 20 m), however the highest abundance of O. trimaculatus occurs at less than 30 m depth. The fishery did not show signs of depletion likely due to the combination of target species depth distribution and fleet characteristics limiting fishers' operability. This provides a unique opportunity to constrain fishing effort and avoid overcapacity, for example by banning larger vessels from the fishery.
Journal of the Marine Biological Association of the United Kingdom, Oct 1, 2007
Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap f... more Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap fishery plan was developed to provide information on the feasibility of their potential extraction. Sampling was carried out using an artisanal shellfish boat in the San Matías Gulf. Nine baited traps, three of each type (cubical, tubular-conical and tubular-pyramidal) were intercalated along a master line. The total number of crabs of each species caught was compared among lines (N=27), types of trap and soaking times (6, 24 and 48 h). A total of 137 traps of 243 traps employed caught crabs. More crabs were caught in the cubical traps than in the other types. Comparisons of numbers of crabs among lines allowed identification of areas having different relative abundances, with an average of 3.56 crabs per trap. The catch of Ovalipes trimaculatus was significantly greater in lines on the 10-m isobath. Two lines, on the 50-m isobath, showed the best results for Platyxanthus patagonicus. The total number of crabs per trap obtained during a soaking time of 6 h was significantly less than the number caught with longer soaking times. Only individuals exceeding 50 mm in carapace width were caught. The sizefrequency distributions differed significantly between sexes for the two species, with males larger than females. In O. trimaculatus, males made up 29% of the catch and the remainder was constituted of non-ovigerous females; mean carapace width was 92.93 mm for females and 105.93 mm for males. Forty per cent of P. patagonicus were males (mean carapace width: 99.33 mm). Females bearing eggs amounted to 45% of the total females. Females' mean carapace width was 90.58 mm. Based on the results obtained, preliminary suggestions for management of a potential fishery for these species are made within a precautionary approach.
Journal of the Marine Biological Association of the United Kingdom, May 11, 2012
Population characteristics can be influenced by specific factors of the habitat and the natural v... more Population characteristics can be influenced by specific factors of the habitat and the natural variability of populations can confuse the effect related to protected environments. This study compares the demographic characteristics of Octopus tehuelchus in three coastal environments: two Marine Protected Areas (San Antonio Bay (SAB) and Islote Lobos (IL)) and a traditional fishing zone (El Fuerte (EF)). Weight-frequency distributions, sex-ratio and recruitment were monthly compared between the three intertidal zones. Octopus tehuelchus was smaller in IL, where fishing intensity is lower or null, and reached the largest sizes in the main fishing area of EF and within SAB (where there is no regulation and a mid-high fishing intensity). The sex proportion in SAB and EF was 1:1 all along the year. Although the proportion of mature females in IL was higher, the highest recruitment was observed in EF (the traditional fishing ground). These new data suggest that previous studies, which reported that Marine Protected Areas have positive effects for O. tehuelchus populations, can no longer be supported, and highlight the importance of understanding and quantifying the magnitude and range of natural variability in each environment when assessing the effectiveness of Marine Protected Areas.
Fil: Avaca, Maria Soledad. Universidad Nacional del Comahue. Centro de Investigacion Aplicada y T... more Fil: Avaca, Maria Soledad. Universidad Nacional del Comahue. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni". - Provincia de Rio Negro. Ministerio de Agricultura, Ganaderia y Pesca. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni". - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni"; Argentina
Journal of the Marine Biological Association of the United Kingdom, Aug 11, 2015
Understanding the variables (biotic or abiotic) controlling coastal communities is the main goal ... more Understanding the variables (biotic or abiotic) controlling coastal communities is the main goal of ecology research and it is crucial to predict how communities will evolve under the increasing pressure on coastal systems by human activities. The general aims of this study were to assess the variables affecting the distribution of the fast-growing spongeHymeniacidoncf.perlevis, and to evaluate if physical stressful conditions have an influence in the relationship betweenHymeniacidonand the sea lettuceUlva lactuca. Specifically, the aims were to evaluate the abundance patterns ofHymeniacidonandUlvaand to assess the relationship ofUlvaand physical variables on the abundance ofHymeniacidonat both intertidal and subtidal.HymeniacidonandUlvashowed opposite abundance patterns.Hymeniacidonwas more abundant in sites withoutUlva, and negatively correlated withUlvaabundance at both heights. IntertidalHymeniacidonabundance was not correlated with physical variables, but subtidalHymeniacidonwas.
Over the last two decades, an increasing interest has arisen in the responses of primary producer... more Over the last two decades, an increasing interest has arisen in the responses of primary producers to global-change drivers and, more recently, in the need to consider how those various drivers may interact. To understand how Corallina officinalis (hereafter Corallina) can be affected by future changing conditions, we investigated the short-term direct effects of co-occurring increased nutrient loads, solar radiation, and lower pH, assessing how these clustered drivers affected Corallina's overall physiological performance in a harsh Patagonian coastal environment. To describe the seasonal trend of the physiological parameters in the field, we sampled subtidal Corallina to determine their net oxygen production (NOP), pigments, and carbonate content (CC). Furthermore, we conducted seasonal 10-days experiments, simulating the conditions predicted for the year 2100 by the IPCC (RCP 8.5) —manipulating pH, nutrients, and irradiance—along with the current conditions. The pigments and carotenoids/chlorophyll-a ratio were, in general, constant in the field over the seasons; but the NOP and CC dropped in spring, when the carotenoids peaked. After the experiment, the highest carotenoid/chlorophyll-a ratio was registered in summer under both the currentand the predictedconditions and in winter under the predictedcondition. This lower physiological status was also reflected in almost all other variables. Thus, Corallina may display an acclimatation strategy to cope with high ultraviolet-radiation levels by adjusting its pigment composition to avoid photoinhibition. An understanding of how Corallina, as a habitat-forming species, will respond to future global-change may provide clues about the extent of effects on the ecosystem functions and services.
Developments in Aquaculture and Fisheries Science, 2006
Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scall... more Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scallop) and Zygochlamys patagonica (Patagonic scallop), their fisheries, and experimental results that have significance in the future development of aquaculture. The fisheries supported by these two species are radically different from each other. The Tehuelche scallop is the target of small inshore fisheries in the gulfs of northern Patagonia, and involves dredging and commercial diving. In spite of the small volumes landed, these fisheries are of considerable significance for the local economies. The Patagonic scallop fishery is an industrial operation conducted by three or four factory trawlers that process the catch at sea. Catches in the order of 50,000 tons yr -1 now rank this species among the most important scallop fisheries in the World. The Tehuelche scallop is a simultaneous hermaphrodite and is iteroparous. The Tehuelche scallop may do quick and brief swimming movements as an escape response to the predators or other disturbances.
ABSTRACT The radular morphology of Zidona dufresnei was studied by optical and scanning electron ... more ABSTRACT The radular morphology of Zidona dufresnei was studied by optical and scanning electron microscopy. We analysed the variability among and within three populations distributed along the southwestern Atlantic Ocean coast, considering the hypothesis that the isolation among populations favours adaptive phenotypic variation, which is also expressed at the radular level. Populations selected for this study differ in their maximum individual size, growth rate, size and age at maturity, and fecundity. This study provides the first analysis of the interpopulational variability of the radula of Zidona dufresnei and the first description of its morphology. Zidonia dufresnei exhibited a rachiglossate radulae composed of rows of tricuspid teeth (radular formula: 0+R+0). No differences in tooth shape among populations and sexes were observed. However, significant interpopulational differences in the height of the rachidian cusp and total length of the radula were detected. Specimens from San Antonio Bay showed the lowest values for all radular variables. Positive significant relationships between total shell length and the height of the rachidian cusp and total length of the radula were found, while the number of rows remained relatively constant regardless of size. The larger morphotypes had a longer radula because of an increase in the height of the rachidian cusp. No sexual dimorphism was observed in any morphometric variables of the radula. The results suggest that populations distributed along the Argentine Sea are homogeneous for radular morphology, despite the differences in life history traits, which may be linked to a similarity in feeding habits across populations.
The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stre... more The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stresses increase, habitat amelioration by ecosystem engineers becomes more relevant. Moreover, the individual-and population-level traits of ecosystem engineers can affect their ability to reduce environmental stress. On the Patagonian shores of Argentina (SW Atlantic, 41°S), the intertidal community is exposed to harsh conditions. We predicted that in this severe environment, variation in the above-ground structure of the smooth cordgrass Spartina alterniflora should buffer the physical stress on the substrate through shading and reduction of wind and water flow energy, ultimately affecting the sediment properties and microphytobenthic biomass. To test this hypothesis, we experimentally manipulated cordgrass density at the edge and inner marsh of a S. alterniflora meadow during both summer and winter. In summer, evaporation and temperature were higher in clipped plots, while in winter, evaporation varied across densities and location treatments, with higher sediment water content in the inner marsh. No effect of S. alterniflora density or location were observed on sediment organic matter or chl a concentration, and mean sediment grain size was always smaller inside the marsh. In summer, extracellular polymeric substance (EPS) content was higher in clipped plots inside the marsh, however this did not differ from the other density treatments at this location. Overall, shading had weak effects on sediment properties and microphytobenthic biomass, and most observed differences were attributable to grain size. We speculate that the harsh conditions of this system overwhelm the ecosystem engineering effects of S. alterniflora, probably because of its relatively small aboveground biomass.
The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stre... more The magnitude of the outcome of ecosystem engineering is context-dependent; as environmental stresses increase, habitat amelioration by ecosystem engineers becomes more relevant. Moreover, the individual-and population-level traits of ecosystem engineers can affect their ability to reduce environmental stress. On the Patagonian shores of Argentina (SW Atlantic, 41°S), the intertidal community is exposed to harsh conditions. We predicted that in this severe environment, variation in the above-ground structure of the smooth cordgrass Spartina alterniflora should buffer the physical stress on the substrate through shading and reduction of wind and water flow energy, ultimately affecting the sediment properties and microphytobenthic biomass. To test this hypothesis, we experimentally manipulated cordgrass density at the edge and inner marsh of a S. alterniflora meadow during both summer and winter. In summer, evaporation and temperature were higher in clipped plots, while in winter, evaporation varied across densities and location treatments, with higher sediment water content in the inner marsh. No effect of S. alterniflora density or location were observed on sediment organic matter or chl a concentration, and mean sediment grain size was always smaller inside the marsh. In summer, extracellular polymeric substance (EPS) content was higher in clipped plots inside the marsh, however this did not differ from the other density treatments at this location. Overall, shading had weak effects on sediment properties and microphytobenthic biomass, and most observed differences were attributable to grain size. We speculate that the harsh conditions of this system overwhelm the ecosystem engineering effects of S. alterniflora, probably because of its relatively small aboveground biomass.
Journal of the Marine Biological Association of the United Kingdom, Apr 21, 2015
Growth rates and size-age at maturity are life history traits that combine in different ways to a... more Growth rates and size-age at maturity are life history traits that combine in different ways to achieve maximal fitness. The marine scavenger Buccinanops globulosus was used as a model to explore the variation on female size-age at maturity and reproductive effort among three populations characterized by different growth rates (slow, moderate and rapid). This species constitutes the target of an artisanal fishery in North Patagonia. Here, a suite of different estimators of size-age at maturity derived from gonad histological analysis and the study of females carrying egg capsules were obtained. Data were modelled using a logistic function and the maturity patterns were compared among populations. We found that female size and age at maturity were variable and site-specific. The fastest-growing population showed the lowest reproductive effort. Slow and rapid-growing females mature at different sizes but at the same age whereas moderate-growing females mature both at a different size and age (intermediate size and at earlier age). Thus, results obtained here are difficult to reconcile with a single reaction norm for a single genotype in the studied populations. Growth rate variation is not enough to explain the patterns described here. The information provided could be used for the establishment of fishery management actions, such as minimum landing size.
A cohort of juveniles Aequipecten tehuelchus was obtained on collectors placed in the San Matı́as... more A cohort of juveniles Aequipecten tehuelchus was obtained on collectors placed in the San Matı́as Gulf in the 1997–1998 reproductive season, and was cultivated in circular lantern nets or screened plastic trays. An additional trial using the “ear hanging” method was ultimately terminated due to formation of excessive biofouling on the shells, although some growth and survival data were obtained
ABSTRACT Feeding decisions under predation risk can be a key in the life of scavenger organisms, ... more ABSTRACT Feeding decisions under predation risk can be a key in the life of scavenger organisms, and tuned recognition of predation alarm cues and flexibility in the response are fundamental. The effect of injured conspecifics on the response behavior of the whelk Buccinanops globulosum to feeding opportunities was experimentally evaluated in a Patagonian Bay (40°45′S, 64°56′W, Argentina) in September 2010. The effect of sex, size, body condition, or starvation on anti-predatory behavior was assessed. The number of B. globulosum feeding on carrion was reduced by half when damaged conspecifics were present. Smaller, lighter, and starved individuals responded less to the presence of damaged conspecifics. These results indicate that, under natural conditions, feeding avoidance after detecting damaged conspecifics is a common and important anti-predatory strategy of B. globulosum and show that morphology and starvation are significant factors in the context of the trade-off between feeding and avoiding predation risk.
Journal of the World Aquaculture Society, Mar 1, 1995
Studies on larval settlement and growth of the commercial scallop Aeguipcten tehuelchus were carr... more Studies on larval settlement and growth of the commercial scallop Aeguipcten tehuelchus were carried out over a 2-yr period in San Matias Gulf, Argentina. Gonadal index was used to indicate spawning and spat collectors were deployed when spawning began. Artificial spat collectors (monofilament bags filled with thin shrub branches) were placed at a depth of 25 m in two areas of the Gulf during two seasons (1989-1990 and 1991-1992). Maximum settlement occurred by mid-February during the first season and by midJanuary in the second season. Larger numbers of spat were found in collectors placed near the sea bottom. After settlement, spat were removed and placed in cages for growout. Scallops reached the average commercial size (60 mm shell height) 16 mo later. Mortality rate during the entire period was 10%.
Experiments on fertilization (self-fertilization and cross-mating), embryonic density, larval fee... more Experiments on fertilization (self-fertilization and cross-mating), embryonic density, larval feeding, survival and larval settlement on natural substrata were carried out in order to identify some of the basic requirements of the early life history of Aequipecten tehuelchus reared under hatchery conditions.In self-fertilization, the main developmental stages were represented by the initial stages, mainly nonfertilized oocytes and embryos going through early
Abstract Time-series of fishing position, landings, satellite-derived sea-surface temperature and... more Abstract Time-series of fishing position, landings, satellite-derived sea-surface temperature and chlorophyll a concentrations were used to relate the spatial–temporal distribution of the Argentine hake Merluccius hubbsi with seasonal oceanographic processes in San Matías Gulf. Also, the seasonal effect of fishing on the hake population structure was analysed. During summer the fleet was concentrated over the area of the frontal system, obtaining the best catch-per-unit-effort (CPUE) of hake in relatively deep waters. In autumn, the dispersion of the fleet due to a reduction in CPUE coincided with the dissipation of the front, suggesting that the distribution and shoaling of the Argentine hake is associated with seasonal thermal structures. In spring, the thermal structure of the waters and the chlorophyll a blooms seem to modulate the timing of spawning of hake, which occurs mainly in October–November. In addition, the fleet captured a higher proportion of females in the gonadal recovery stage during warm months (November–April). While winter catches (May–October) consisted mainly of males, the intense summer fishing may result in a high impact on the female population. This information is relevant to design of spatial management tools intended to provide biological sustainability to the hake fishery.
The relationship between the pinnotherid crab Tumidotheres maculatus and its scallop host Aequipe... more The relationship between the pinnotherid crab Tumidotheres maculatus and its scallop host Aequipecten tehuelchus was studied over an annual cycle from November 1999 to November 2000, on a scallop bank in the NW sector of the San Matías Gulf, Argentina. T. maculatus was found within the mantle cavity of the scallop. The female crabs were larger than the males, and the proportion of females was always larger than that of males, in some months reaching 100%. Carapace lengths of the crabs varied from 1 to 16 mm. Most infested scallops contained a single crab. Infestation with one gravid female excluded the presence of other females. The level of infestation (prevalence) varied between 14.3 and 50.0%. No relationship was observed between the prevalence of the crabs and depths occupied by the scallops. As scallops grew, the weight gain of non-infested scallops was greater than those infested (ANCOVA; P < 0.01). Indices of meat yield (muscle, gonad) of individuals not infested with T. maculatus were greater than indices of infested scallops (ANOVA; P < 0.05), indicating a parasitic relationship. The effect of crab infestation on the scallop industry is discussed.
The fishery for the swimming crab Ovalipes trimaculatus in the southwestern Atlantic started in 2... more The fishery for the swimming crab Ovalipes trimaculatus in the southwestern Atlantic started in 2007, with an average catch of 64.36 t⋅y −1 during the period between 2008 and 2013. The fishery is under an open access regime and market demand exceeds the catch which raises concern about its future. It is also data-poor, which prevents researchers from using traditional assessment methods. The factors that limit the fishing effort were identified by analyzing the fishing operation, the decision making process of the fishers and CPUE. Changes in catch composition through space and time, and the distribution of the population along a depth gradient were also studied. Wind, recent yield and the price of crab were perceived by skippers as relevant factors when deciding to go fishing, but there was no relationship between these variables and monthly fishing effort. However, daily fishing effort depended on wind conditions. During the studied period (2008-2013) the CPUE of 2009 was the only one lower than the CPUE of 2008, and the number of fishing grounds as well as their respective area have not increased. The species depth distribution reaches 60 m deep, which is much deeper than the depths divers can reach (about 20 m), however the highest abundance of O. trimaculatus occurs at less than 30 m depth. The fishery did not show signs of depletion likely due to the combination of target species depth distribution and fleet characteristics limiting fishers' operability. This provides a unique opportunity to constrain fishing effort and avoid overcapacity, for example by banning larger vessels from the fishery.
Journal of the Marine Biological Association of the United Kingdom, Oct 1, 2007
Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap f... more Crab species had not been exploited until recently in the San Matías Gulf. An experimental trap fishery plan was developed to provide information on the feasibility of their potential extraction. Sampling was carried out using an artisanal shellfish boat in the San Matías Gulf. Nine baited traps, three of each type (cubical, tubular-conical and tubular-pyramidal) were intercalated along a master line. The total number of crabs of each species caught was compared among lines (N=27), types of trap and soaking times (6, 24 and 48 h). A total of 137 traps of 243 traps employed caught crabs. More crabs were caught in the cubical traps than in the other types. Comparisons of numbers of crabs among lines allowed identification of areas having different relative abundances, with an average of 3.56 crabs per trap. The catch of Ovalipes trimaculatus was significantly greater in lines on the 10-m isobath. Two lines, on the 50-m isobath, showed the best results for Platyxanthus patagonicus. The total number of crabs per trap obtained during a soaking time of 6 h was significantly less than the number caught with longer soaking times. Only individuals exceeding 50 mm in carapace width were caught. The sizefrequency distributions differed significantly between sexes for the two species, with males larger than females. In O. trimaculatus, males made up 29% of the catch and the remainder was constituted of non-ovigerous females; mean carapace width was 92.93 mm for females and 105.93 mm for males. Forty per cent of P. patagonicus were males (mean carapace width: 99.33 mm). Females bearing eggs amounted to 45% of the total females. Females' mean carapace width was 90.58 mm. Based on the results obtained, preliminary suggestions for management of a potential fishery for these species are made within a precautionary approach.
Journal of the Marine Biological Association of the United Kingdom, May 11, 2012
Population characteristics can be influenced by specific factors of the habitat and the natural v... more Population characteristics can be influenced by specific factors of the habitat and the natural variability of populations can confuse the effect related to protected environments. This study compares the demographic characteristics of Octopus tehuelchus in three coastal environments: two Marine Protected Areas (San Antonio Bay (SAB) and Islote Lobos (IL)) and a traditional fishing zone (El Fuerte (EF)). Weight-frequency distributions, sex-ratio and recruitment were monthly compared between the three intertidal zones. Octopus tehuelchus was smaller in IL, where fishing intensity is lower or null, and reached the largest sizes in the main fishing area of EF and within SAB (where there is no regulation and a mid-high fishing intensity). The sex proportion in SAB and EF was 1:1 all along the year. Although the proportion of mature females in IL was higher, the highest recruitment was observed in EF (the traditional fishing ground). These new data suggest that previous studies, which reported that Marine Protected Areas have positive effects for O. tehuelchus populations, can no longer be supported, and highlight the importance of understanding and quantifying the magnitude and range of natural variability in each environment when assessing the effectiveness of Marine Protected Areas.
Fil: Avaca, Maria Soledad. Universidad Nacional del Comahue. Centro de Investigacion Aplicada y T... more Fil: Avaca, Maria Soledad. Universidad Nacional del Comahue. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni". - Provincia de Rio Negro. Ministerio de Agricultura, Ganaderia y Pesca. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni". - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Centro Nacional Patagonico. Centro de Investigacion Aplicada y Transferencia Tecnologica en Recursos Marinos "Almirante Storni"; Argentina
Journal of the Marine Biological Association of the United Kingdom, Aug 11, 2015
Understanding the variables (biotic or abiotic) controlling coastal communities is the main goal ... more Understanding the variables (biotic or abiotic) controlling coastal communities is the main goal of ecology research and it is crucial to predict how communities will evolve under the increasing pressure on coastal systems by human activities. The general aims of this study were to assess the variables affecting the distribution of the fast-growing spongeHymeniacidoncf.perlevis, and to evaluate if physical stressful conditions have an influence in the relationship betweenHymeniacidonand the sea lettuceUlva lactuca. Specifically, the aims were to evaluate the abundance patterns ofHymeniacidonandUlvaand to assess the relationship ofUlvaand physical variables on the abundance ofHymeniacidonat both intertidal and subtidal.HymeniacidonandUlvashowed opposite abundance patterns.Hymeniacidonwas more abundant in sites withoutUlva, and negatively correlated withUlvaabundance at both heights. IntertidalHymeniacidonabundance was not correlated with physical variables, but subtidalHymeniacidonwas.
Over the last two decades, an increasing interest has arisen in the responses of primary producer... more Over the last two decades, an increasing interest has arisen in the responses of primary producers to global-change drivers and, more recently, in the need to consider how those various drivers may interact. To understand how Corallina officinalis (hereafter Corallina) can be affected by future changing conditions, we investigated the short-term direct effects of co-occurring increased nutrient loads, solar radiation, and lower pH, assessing how these clustered drivers affected Corallina's overall physiological performance in a harsh Patagonian coastal environment. To describe the seasonal trend of the physiological parameters in the field, we sampled subtidal Corallina to determine their net oxygen production (NOP), pigments, and carbonate content (CC). Furthermore, we conducted seasonal 10-days experiments, simulating the conditions predicted for the year 2100 by the IPCC (RCP 8.5) —manipulating pH, nutrients, and irradiance—along with the current conditions. The pigments and carotenoids/chlorophyll-a ratio were, in general, constant in the field over the seasons; but the NOP and CC dropped in spring, when the carotenoids peaked. After the experiment, the highest carotenoid/chlorophyll-a ratio was registered in summer under both the currentand the predictedconditions and in winter under the predictedcondition. This lower physiological status was also reflected in almost all other variables. Thus, Corallina may display an acclimatation strategy to cope with high ultraviolet-radiation levels by adjusting its pigment composition to avoid photoinhibition. An understanding of how Corallina, as a habitat-forming species, will respond to future global-change may provide clues about the extent of effects on the ecosystem functions and services.
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Papers by Maite Narvarte