bluuebunny/crossref_metadata_2025 huggingface dataset:
Applying biomass dynamic models to the southern horse mackerel stock (Atlantic waters of Iberian Peninsula). A comparison with VPA-based methods
Authors: Abaunza Pablo , Fariña A. Celso , Murta Alberto
Published: October 2008

The horse mackerel (Trachurus trachurus) fishery of the Northeast Atlantic, is currently subject to assessment and management in the ICES area. Assessment of the Southern horse mackerel (ICES Divisions VIIIc and IXa) is made with Virtual Population Analysis (VPA), using time series of catch-at-age data and catch-per-unit-of-effort (CPUE) from 1985 to present. The application of biomass-dynamic models to the assessment and catch prediction of this stock has never been attempted before. In this paper, a production model is applied to the Southern horse mackerel stock. To quantify uncertainty in parameter estimates, bootstrap confidence intervals were computed, which showed that estimates could be considered as reliable. The bootstrap standard deviations of Ft, r, MSY and FMSY were relatively small, despite the lack of trends in the available effort series. On the contrary, the catchability, q, showed a coefficient of variation of 74%. The current level of fishing mortality for 1998 was considered as unsustainable for the resource, being well above FMSY according to the biomass-dynamic models, and above Fpa according to the age-structured model. Both models were in close agreement on the time series of fishing mortality and in the perception of the state of the stock. Differences existed in the changes in stock biomass especially over the last years. Over this time period the age-structured model showed an increasing trend in biomass. The estimates of MSY and FMSY were in accordance with the precautionary approach philosophy. The biomass-dynamic model used here was usefully applied to the Southern horse mackerel stock, giving complementary information to the age-structured model, both in the perception of the state of the stock and in the definition of management targets.
An evaluation of management strategies for Atlantic tuna stocks
Authors: Kell L. T. , Die D. J. , Restrepo V. R. , Fromentin J. M. , Ortiz de Zarate V. , Pallares P.
Published: October 2008

International agreements for the International Commission for the Conservation of Atlantic Tunas (ICCAT) convention area imply that Atlantic tuna stocks should be managed by strategies based on maximum sustainable yield (MSY); however, there is concern whether this will actually ensure sustainability with sufficiently high probability consistent with the principals of the precautionary approach. Therefore, the performance of MSY management strategies based on current assessment procedures was evaluated using a computer simulation framework. The framework includes the data collection, assessment, prediction, and management processes, as well as the implementation of management regulations. It therefore provides an integrated way to evaluate the relative importance of and the interactions between each component of the system with regard to the overall success of the management strategy. The study elucidates guidelines about assessment and management that are general enough to be applied to all tunas in the Atlantic Ocean. It does so by comparing different hypotheses about management and assessment for three stocks (North Atlantic albacore, Atlantic bigeye and East Atlantic skipjack), which are representative of the variety encountered (i.e. from data rich to poor and tropical to temperate waters) in ICCAT stocks. Management performance was especially sensitive to the carrying capacity of the stock. The type of proxy used for MSY was more important to the success of the procedure than the frequency of assessment or the number of indices used in the assessment. Whilst the procedure was successful at achieving the management objectives for albacore, it was only partially successful for bigeye and was too conservative for skipjack.
The East Atlantic and Mediterranean bluefin tuna stock management: uncertainties and alternatives
Authors: Fromentin Jean-Marc
Published: October 2008

Although the Atlantic bluefin tuna has been studied for more than a century, the assessment of the East stock is characterised by a large amount of uncertainty. In 2000, this situation became so critical that quantitative stock assessment has been postponed. The first part of the present study aims to list the main difficulties that have led to the current situation and tries to discern between subjective and objective uncertainty. The former, which is due to an incomplete knowledge of the system and which has increased in the past few years, is mainly due to a decreasing quality of the catch and effort data, that has followed the establishment of a TAC. The latter source of uncertainty, which results from the underlying variability in stochastic processes, mainly relates, for this species, to spatial and temporal changes in stock size, growth and migration. The second part of this study presents the results of simulation modelling, which could be, in the meantime, an useful tool for short-term management of the East Atlantic and Mediterranean BFT stock.
Annual trends in catchability and fish stock assessments
Authors: Paul Marchal , Clara Ulrich , Knut Korsbrekke , Martin Pastoors , Brian Rackham
Published: October 2008

A key assumption of many fish stock assessment models is that catchability is constant over time. We assume here that trends in catchability may occur through fishing power creeping. The tuning fleets, which are prone to fishing power development, may be identified using the Hybrid method. A range of catchability trends, including values derived from the Hybrid method, is then implemented to standardise the fishing effort of some tuning fleets used in the stock assessments performed by XSA (eXtended Survivors Analysis). Stocks being assessed are the North Sea cod, saithe, plaice and sole. The performances of the new and traditional XSA assessments are compared using criteria based on the precision of catchability estimates, stationarity of Log-catchability residuals and retrospective patterns relative to fishing mortality, spawning stock biomass and recruitment estimates. The performances of the North Sea cod, plaice and sole assessments could be enhanced by accounting for an overall annual increase in the catchability of some of the tuning fleets. No significant trends could be detected in the catchability of the tuning fleets relative to the assessment of the North Sea saithe. By contrast with the traditional assessment, the spawning biomass of cod is expected not to have increased between 1997 and 1998, while the fishing mortality of sole is expected to have increased over the same period.
Effect of refuge supplement on Audouin's gull chick survival
Authors: Prieto Jordi , Jover Lluís , Ruiz Xavier
Published: October 2008

One of the main threats to Audouin´s gull (Larus audouinii) at Chafarinas Islands is predation on eggs and chicks by the yellow-legged gull (Larus cachinnans). During the 1999 and 2000 breeding seasons we tested the effects of supplementary refuge availability on chick survival. Well before the laying period, nine adjacent enclosures were erected inside Audouin´s gull´s breeding grounds and some of them were supplied with artificial refuges. Our results showed significantly greater chick survival in the enclosures with artificial refuges than in control ones. In 2000, an overall lower breeding success of Audouin´s gull and a dilution of the refuge effect were observed. These results were probably related to food-shortage that year. We suggest that, along with other factors, an increase in refuge availability may significantly enhance Audouin´s gull chick survival.
Growth of Audouin's gull chicks: the role of prehatch and posthatch factors
Authors: Villuendas Elena , Sarzo Blanca
Published: October 2008

We compared the growth rates of Audouin´s Gull (Larus audouinii) chicks from the Ebro Delta and Columbretes Islands. Chicks from the Columbretes Islands were reared in captivity and fed ad libitum. Wild chicks from the Ebro Delta weighed more than chicks hatched from Columbretes eggs but attained a lower weight at fledging. Chicks from Columbretes eggs hatched with a longer wing length but rates did not differ between samples during the early stages of growth. Eggs from the Ebro Delta were significantly larger than eggs from Columbretes. Hence, differences in growth appeared not to be related to differences in egg size (prehatch factor) but only in parental quality (posthatch factor) through the amount of food delivered to chicks. These differences could be due to the incapacity of parents to provide enough food during the last stages of chick development, in part because of reduced food availability at the Ebro Delta during the study period. Alternatively, differences could be attributed to a trade-off between present and future reproduction. Demographic consequences of reduced food availability for the 1993 Ebro Delta cohort should be explored in future work.
Recent changes in the summer distribution of the Balearic shearwater Puffinus mauretanicus off western France
Authors: Yésou Pierre
Published: October 2008

Surveys carried out in the 1980s showed that 8,000-10,000 Balearic shearwaters regularly gathered in inshore waters of central and northern Biscay, particularly off the coast of Vendée and in the Mor-Braz area, western France. This distribution, apparently linked to particular oceanographical conditions (thermal front), was strikingly overlapping with that of clupeid fish, particularly anchovies. Recent surveys (1999-2000) have shown that the species has become far less numerous in these "traditional" haunts. Conversely, its abundance has increased in the western Channel, some hundreds of kilometres to the North, during the 1990s. Reasons for this northward shift (e.g. changes in prey distribution due to fishing activities or water warming in Biscay) remain hypothetical and further study is needed.
Geographical patterns of seabird attendance to a research trawler along the Iberian Mediterranean coast
Authors: Abelló Pere , Arcos José Manuel , Gil Sola Luis
Published: October 2008

The attendance of seabirds to a research trawler along the Mediterranean coast of the Iberian Peninsula was monitored during six demersal surveys (MEDITS project). Cruises were performed in late spring during the period 1994-1999. Twenty seabird species were recorded, including both breeders and migrants. The four most common species behind the boat were local breeders, namely the Balearic shearwater Puffinus mauretanicus, Cory´s shearwater Calonectris diomedea, Audouin´s gull Larus audouinii and the yellow-legged gull Larus cachinnans. Most seabirds made use of trawler discards to some extent, with the exception of the Puffin Fratercula arctica. Geographically consistent patterns were identified in the six years surveyed. Seabirds were most abundant along the eastern coast of Iberia, especially off the Ebro Delta and around the Columbretes Islands, coinciding with one of the major areas of primary productivity and one of the largest trawling fleets in the western Mediterranean. The location of the main seabird colonies also influenced the distribution of breeders.
Predation on common tern eggs by the yellow-legged gull at the Ebro Delta
Authors: Hernández-Matías Antonio , Ruiz Xavier
Published: October 2008

The Ebro Delta holds a large seabird community, including a common tern (Sterna hirundo) local population of 3,085 pairs in 2000 which breeds scattered in several colonies. At El Canalot colony, 1,178 (1999) and 1,156 pairs (2000) of this species bred distributed in 32 and 38 sub-colonies respectively. These sub-colonies varied in size from 1 to 223 pairs and were placed near the main breeding colonies of yellow-legged gulls (Larus cachinnans) and Audouin´s gulls (L. audouinii), which are potential egg-predators of terns. We studied egg predation during 1999 (6 sub-colonies) and 2000 (27 sub-colonies). Overall, we found that 10.6% of the nests in 1999 and 16.7% in 2000 suffered partial or total egg predation, being total in 81.1% of the predatory events. Predation was significantly higher in small sub-colonies (< 11 pairs): 49.4% in 1999 and 75.5% in 2000. Only attacks from yellow-legged gulls were observed, and defence behaviour of terns was significantly more frequent against this gull species (40.5 hours of observation), suggesting that in most cases the egg predation recorded was due to this species. Probability of egg predation was significantly and negatively correlated with distance to the nearest yellow-legged gull sub-colony, although this relationship was no more significant after adjustment for sub-colony size. On the other hand, distance to the nearest Audouin´s gull sub-colony did not show any effect. Our results suggest that the impact of large gulls (at least yellow-legged gulls) upon smaller seabirds breeding in the area might be important, especially when they are breeding in small sub-colonies. Further studies are needed to analyse the general impact of large gulls upon the breeding populations of other colonial bird species in the area.
Distribution of Calanus spp. as determined using a genetic identification system
Authors: Lindeque Penelope K. , Harris Rober P. , Jones Malcolm B. , Smerdon Gary R.
Published: October 2008

The morphological similarity of Calanus species necessitates that the only unambiguous way of discriminating between the different species at any developmental stage is with molecular tools. We have developed a simple molecular technique to distinguish between the four species of Calanus copepods found in the North Atlantic (Calanus helgolandicus, C. finmarchicus, C. glacialis and C. hyperboreus) at any life stage. This system involves the PCR amplification of a region of the 16S rRNA gene, followed by Restriction Fragment Length Polymorphism (RFLP) analysis of the amplified product. This paper describes the application of the technique to a number of Calanus samples taken from a wide geographical range within the North Atlantic. Samples were acquired from sites ranging in latitude from the English Channel (50°N) to Tromsø (69°N), including many regions of co-occurrence. A comparison has been made between the distribution of Calanus as determined by molecular techniques and distributions established using traditional morphological identification. The molecular analysis has clearly shown extended areas of distribution and co-occurrence and has confirmed the intraspecific conservation of the restriction sites and therefore the reliability of the technique.
Deep macrobenthic communities from Nazaré Submarine Canyon (NW Portugal)
Authors: Cúrdia J. , Carvalho S. , Ravara A. , Gage J. D. , Rodrigues A. M. , Quintino V.
Published: October 2008

Macrofauna community structure within Nazaré Submarine Canyon is analysed and used to assess the potential effects of natural enrichment in this area subjected to accumulation of coastal sediments. A transect including three stations (2894, 3514 and 4141 m) was carried out in the Nazaré Submarine Canyon (NW Portugal) during a cruise of OMEX II programme (Ocean Margin Exchange), in the winter season of 1999. Although data was not collected in order to calculate sedimentation rates, sampling station at 2894 m is located in an area characterised by high levels of sedimentation, thus a high amount of organic matter is expected to be available for the local communities. Faunistic data are discussed in the context of the different features of the stations sampled. Multivariate analysis clearly separates the shallowest station from the other ones, which otherwise appear to be very similar. It also revealed a perceptible gradient along sediment depth at all stations, from shallow to deeper layers. Exceptionally depressed species richness and low evenness values were observed at the 2894 m station. The high number of individuals of a single species, Cossura sp. A, and the atypical diversity, dominance and evenness values obtained for this station support the hypothesis of community disturbance due to organic enrichment.
Metabolic CO2 production in the Mediterranean Sea: A case study for estimating carbon budget in the sea
Authors: La Ferla Rosabruna , Azzaro Maurizio
Published: October 2008

A synthesis of published metabolic CO2 production rates determined in the water column of the Eastern Mediterranean Sea from 1993 to 1999 is reported with the aim of furnishing an overall picture of the remineralization processes occurring in the basin. The trends of the remineralization are also interpreted with respect to the so-called Eastern Mediterranean Transient (EMT) event. This study augments the sparse data set of respiration measurements, from oceanographic surveys, and highlights the tight coupling between biological processes and circulation patterns. In the photic zone, the rates decreased from West to East as well as from North to South. In the aphotic zone, the C remineralization trend followed the traditional routes of intermediate and deep waters in the Eastern Mediterranean Basin, and underwent the important modifications into the depths as a consequence of the EMT impact.
Plankton biodiversity around the Salento Peninsula (South East Italy): an integrated water/sediment approach
Authors: Moscatello Salvatore , Rubino Fernando , Saracino Orestina D. , Fanelli Giovanni , Belmonte Genuario , Boero Ferdinando
Published: October 2008

The microplankton community was studied at 9 sites (29 sampling stations) along the Salento Peninsula (SE Italy). Integrated samplings from both the water column (to collect active stages), and sediments (to collect resting stages), were carried out. More than 400 taxa were recognised in total. As for phytoplankton, 64 taxa were new records from the area. In particular, 16 of them were found only as resting stages in the sediments. A harbour, a coastal lake, and a submerged cave were investigated to understand the role of confined or sheltered environments in the accumulation of resting stages. The harbour and the lake were found to be biodiversity reservoirs, due to the abundance of resting stages in their sediments. Only few species were found both in the water column, as plankton, and in the sediments, as resting stages. Furthermore, the most abundant species in the water column were not equally dominant as resting stages in the sediments. This suggests that species other than those observed in the plankton during the present work (i.e., those found as dominant among resting stages in the sediments) dominated the plankton in the past. Furthermore, they could dominate the future plankton, with multiannual cycles, starting from sediment reservoirs. The search for resting stages in the sediment, thus, is useful to discover temporarily rare species, because species persist in the sediments as resting stages for longer periods than those spent as active stages in the plankton.
Mediterranean and Atlantic deep-sea fish assemblages: differences in biomass composition and size-related structure
Authors: Massutí Enric , Gordon John D.M. , Morata Joan , Swan Sarah C. , Stefanescu Constantí , Merrett Nigel R.
Published: October 2008

Data obtained over a period of twenty years from 214 bottom trawls, towed on a single warp at depths between 402 and 1993 m in the western Mediterranean (Algerian and Balearic basins) and eastern North Atlantic (Rockall Trough and Porcupine Seabight), allowed a standardised comparison of density, biomass composition and size-related structure for both the whole fish fauna and for the most common species found within the deep-sea fish assemblages. All four areas are characterised by distinctly different and well-documented oceanographic conditions, biogeographical affinities and fishing exploitation. The results showed clear differences between the Atlantic and the Mediterranean deep-sea fish fauna, not only in density, species richness and composition, but also in the structure of the biomass that constitutes these assemblages. These differences are discussed in relation to environmental conditions and fishing pattern, which have determined the adaptive responses of both individual species and the whole ecosystem.
Deep-sea Mediterranean biology: the case of Aristaeomorpha foliacea (Risso, 1827) (Crustacea: Decapoda: Aristeidae)
Authors: Politou Chrissi-Yianna , Kapiris Konstantinos , Maiorano Plorzia , Capezzuto Francesca , Dokos John
Published: October 2008

Data on the distribution, abundance and biological parameters of the giant red shrimp Aristaeomorphafoliacea were collected during a research survey in deep waters (600-4000 m) of the Mediterranean Sea at three locations: the Balearic Sea, the western Ionian and the eastern Ionian in early summer 2001. The shrimp was mainly found in the shallower zone (< 1000 m) of the eastern Ionian Sea. Few specimens were caught in the deeper waters of this region, with 1100 m being the lower limit of its distribution. This is the maximum depth reported for the species in the Mediterranean. At the other two locations, the species was scarcely caught and only in the shallowest zone (< 1000 m). In the area and depth zone of high abundance, 5 modal groups for females and 3 for males were distinguished using the Bhattacharya method. The recruitment seems to take place at the shallowest stations (600 m). More than 50% of adult females were in advanced maturity stages. The striking abundance differences of the species between the western and eastern locations may be explained by the different exploitation level of the deep waters (almost null in the eastern Ionian Sea and extensive more westwards). However, the distribution and biological characteristics of A.foliacea indicate a higher vulnerability to over-fishing comparing to the other commercial co-occurring deep-water shrimp Aristeusantennatus.
Body fish size tendencies within and among species in the deep-sea of the western Mediterranean
Authors: Moranta Joan , Palmer Miquel , Massutí Enric , Stefanescu Constantí , Morales-Nin Beatriz
Published: October 2008

Data collected south-west of the Balearic Islands (Western Mediterranean) on two cruises, Quimera-I (October, 1996) and Quimera-II (May, 1998), were used to establish general ecological patterns in deep-sea fish assemblages. A total of 39 trawls were taken at depths between 400 and 1714 m. Fish assemblages were analysed in terms of species composition, ecological parameters and biomass spectra. Differences in species composition between cruises and depth (Upper slope: 400-800 m, Middle slope: 801-1400 m and Lower slope: 1401-1714 m depth) were evaluated using multivariariate analysis. The most important feature was the existence of a biomass peak at intermediate depths. Moreover, the analysis of the biomass spectra indicated the absence of large individuals at the shallower depth interval considered. To determine the causes of the biomass peak on the middle slope four hypothesis were explored: (1) species richness is higher on the middle slope; (2) the fish assemblage from the middle slope can be characterised by the highest abundance (number of fish/area); (3) species found on the middle slope are larger (the species assemblage is built up by larger species); and (4) there is a trend for the specimens of several species to be larger at the middle slope. The data gathered support that the biomass peak is better explained by the existence of abundance peaks of medium and large-sized species, and by the presence of some of the largest individuals of other large-sized species, in both cases related to specific depth size trends which do not always follow a bigger-deeper trend.
Chondrichthyes species in deep waters of the Mediterranean Sea
Authors: Sion Letizia , Bozzano Anna , D’Onghia Gianfranco , Capezzuto Francesca , Panza Michele
Published: October 2008

Data collected during the DESEAS survey carried out in three areas of the Mediterranean Sea (Balearic Sea, western and eastern Ionian Sea) were used to describe the distribution and abundance of chondrichthyes species at depths between 600 and 4000 m. A total of 8 chondrichthyes species were recorded, 5 of them in the Balearic Sea, 4 in the western Ionian and 6 in the eastern Ionian. A decrease in abundance with depth was observed in each species with the exception of Centroscymnuscoelolepis. The most abundant species were Galeus melastomus and Etmopterusspinax. The depth range of some species was updated. G. melastomus was caught down to 1500 m, exhibiting a smaller-deeper pattern in females, while E.spinax was captured down to 2200 m with a bigger-deeper trend. Mature females of these two sharks were found between 600 and 1500 m. A wide size-range was shown in both species. C.coelolepis was only collected in the Balearic Sea down to 2800 m. The presence of a pregnant female was sampled from a depth of 1500 m. The distribution of the species is discussed in the context of the present knowledge of the Mediterranean ichthyofauna.
Distribution of meiobenthos at bathyal depths in the Mediterranean Sea. A comparison between sites of contrasting productivity
Authors: Tselepides Anastasios , Lampadariou Nikolaos , Hatziyanni Eleni
Published: October 2008

In order to study the distribution of meiobenthos (Metazoa and Foraminifera) at bathyal depths along a west-east productivity gradient in the Mediterranean Sea, stations along the continental slopes of the Balearic Sea, west Ionian and east Ionian Seas were sampled during the DESEAS Trans-Mediterranean Cruise in June-July 2001. Standing stock of total meiobenthos differed considerably among the sampling stations, with marked differences occurring between sampling depths and sites. At 600 m depth, meiobenthic abundances were slightly higher over the Balearic continental slope, whereas at the deeper stations (800 m and 1500-1700 m), abundances were significantly higher in the west Ionian Sea. Significant relationships were found between the abundances of major groups and the chloroplastic pigments, indicating that food availability is a major factor controlling the distribution of meiobenthos. Apart from the overall differences in productivity between the western and eastern Mediterranean Sea, local hydrographic features and topographic differences greatly influence the spatial variability of the environmental parameters within each sub-basin and thus the distribution of meiobenthos in the bathyal zone.
The limit of the sea: the bathyal fauna of the Levantine Sea
Authors: Galil Bella S.
Published: October 2008

In the present study, the fish, molluscs, crustaceans and echinoderms collected at depths between 734 and 1558 m during a series of cruises conducted between 1988 and 1999 off the coast of Israel, supplemented by a photographic survey carried out southwest of Cyprus at a depth of 2900 m, were analysed. The main objectives were to determine the faunal composition of the bathybenthic assemblages in the southeastern Levantine Sea, and to compare them with the western Mediterranean assemblages in order to elucidate whether general trends in their bathymetric distribution and population density may be related to environmental/geographic factors. Considering the sampling effort, the diverse gear used and the extended period of sampling, we may assume that the low number of species and specimens recorded actually reflects a low-diversity, low-density deep water fauna. The faunal scarcity may cause a different parcelling of the populations which is reflected in bathymetric distributions that in many cases extend to greater depths than in the Western Mediterranean. The Levantine bathybenthos is composed of autochthonous, self-sustaining populations of opportunistic, eurybathic species that have settled there following the last sapropelic event.
Deep-sea decapod crustaceans in the western and central Mediterranean Sea: preliminary aspects of species distribution, biomass and population structure
Authors: Company Joan B. , Maiorano Porzia , Tselepides Anastasios , Politou Chrissi Yianna , Plaity Wanda , Rotllant Guiomar , Sardá Francisco
Published: October 2008

Three deep-sea areas in the Mediterranean Sea were sampled using a bottom otter trawl during the DESEAS oceanographic survey carried out from early June to early July 2001, covering an area in the western Mediterranean from 600 to 2800 m in depth and two areas in the central Mediterranean, the western and eastern Ionian Sea from 600 to 4000 m in depth. Decapod crustaceans were one of the dominant megafaunal groups, together with fishes, in terms of both biomass and abundance. A total of 2799 decapod specimens belonging to 32 species were collected. Abundance and biomass of the decapod crustaceans decreased with depth. For depths below 1000 m, a decrease in total decapod biomass was recorded from west to east. From the data reported in this study and data from the available literature, decapod crustaceans display differential depth distributions in the different areas. For the most abundant species, size and sex distributions versus depth gradient were examined to compare intraspecific population structures between the sampling areas. Despite differences, among areas, in the species biomass compositions by depth strata and differences in their overall bathymetric ranges of distribution, intraspecific population structures of the most abundant species seem to follow similar trends for size and sex distribution versus depth gradient between the western and central areas. This might be an indication that the individual species structure their populations according to a similar basic pattern regardless of differences in local environmental features. The results have been discussed in the general context of the environmental features encountered by the species in each of the sampling areas.
Visibility as a factor in the copepod-planktivorous fish relationship
Authors: Rudi Strickler J. , Udvadia Ava J. , Marino John , Radabaugh Nick , Ziarek Josh , Nihongi Ai
Published: October 2008

The question we treat in this contribution is whether or not planktivorous fish can use the motion pattern of planktonic copepods to distinguish these animals from other suspended particles in the water. A targeted overview of the predator-prey relationship is followed by a first report of experiments performed in our laboratory where fish selected between two virtual targets on a TV screen, each target showing a different swimming pattern. The results suggest that fish can perceive temporal visual patterns and select their preferred target after two to ten seconds observing the two moving targets. Implications of these preliminary results are discussed and hypotheses for further research formulated.
Chronobiology: implications for marine resource exploitation and management
Authors: Naylor Ernest
Published: October 2008

Chronobiology began as a curiosity-driven science and now impacts significantly on the science of medicine through medical rhythm research and chronotherapeutics. However, whilst it has long been evident that rational exploitation and management of living organisms and their environments require detailed biological understanding, incorporation of the time-base of living systems into such activities has been slow. Evidence suggests that marine management and conservation strategies, whether directed towards the environment or fisheries, are only slowly taking account of the time-scales of endogenously controlled rhythmic animal behaviour as a basis from which to achieve their objectives. Similarly, in commercial aquaculture practices, there is a need for greater evaluation of the role of photoperiod manipulation and optimization of feeding regimes against the background of the endogenous rhythmicity of the organisms concerned. Correct synchronization of an organism’s endogenous biological oscillators, of tidal and/or daily to annual periodicities, is fundamental to its optimal physiological performance and survival.
Lessons in modularity: the evolutionary ecology of colonial invertebrates
Authors: Hughes Roger N.
Published: October 2008

Benthic colonial invertebrates share with higher plants a modular construction and a sessile adult life. Both types of organism show parallel evolutionary responses to common selective forces, but in contrast to the long-established focus on plants, comparable study of colonial invertebrates has developed relatively recently, largely owing to the application of new techniques in image processing and molecular biology. Species whose life cycles are readily completed under laboratory conditions and whose colonies are easily propagated from cuttings provide powerful models for experimentally investigating fundamental evolutionary problems, including metabolic allometry, the manifestation of ageing and the origin of allorecognition systems. Free of the confounding influences of behavioural manipulation and costs of copulation, colonial invertebrates whose water-borne sperm fertilize retained eggs lend themselves well to the experimental study of cryptic female choice, sperm competition and sexual conflict. In these respects, it will be productive to adopt and extend theoretical frameworks developed for flowering plants to guide experimental investigation of modular animals. Since mate choice occurs at the cellular level in modular animals, reproductive isolation is uncorrelated with morphology and cryptic speciation is likely to be widespread.
Marine microbial ecology in a molecular world: what does the future hold?
Authors: Caron David A.
Published: October 2008

Advances in genetic and immunological approaches during the last few decades have transformed medicine and biomedical research. The human genome and the genomes of numerous model organisms are now fully sequenced. Initial exploitation of this wealth of genetic information has begun to revolutionize research on these species, and the applications derived from it. Progress in understanding the ecology of microorganisms (including marine taxa) has followed closely on the heels of these advances, owing to the tremendous benefit afforded by major technological advances in biomedicine. Through the application of these novel approaches and new technologies, marine microbial ecology has moved from a minor footnote within marine biology and biological oceanography during the 1950s and ‘60s to the focus of much of our present interest in the ocean. During the intervening half-century we have learned a great deal regarding the overall abundances, distributions and activities of microorganisms in the sea. Recognition of the extraordinary diversity of marine microbes, the predominant role that they play in global biogeochemical processes, and the potential for natural or engineered microbial products to benefit humankind, has placed marine microbes in the spotlight of both scientific and popular attention. Our fascination with these minute denizens of the ocean is not likely to wane anytime soon. Recent studies have indicated that we still know relatively little about the breadth of microbial diversity in marine ecosystems. In addition, many (most?) of the predominant marine microbial forms in nature have not yet been brought into laboratory culture. Thus, our knowledge is still rudimentary with respect to the spectra of biochemical, physiological and behavioral abilities of these species, and the study of marine microbes will remain a major focus of investigations in marine science well into the foreseeable future. As a large cadre of researchers moves headlong into this work, we can expect many new discoveries and more paradigm shifts regarding the composition and function of marine microbial communities.
Influence of biotic and abiotic sediment factors on abundance and biomass of harpacticoid copepods in a shallow Antarctic bay
Authors: Veit-Köhler Gritta
Published: October 2008

This study presents data of the first investigation on benthic harpacticoid copepods in Potter Cove, King George Island, Antarctica (62°14’S, 58°40’W) with special emphasis on spatial distribution and relation to environmental factors. In addition to the individual numbers that are normally given, the biovolume of the meiobenthic copepods was measured. It showed great variety due to changes in abundance and habitat preferences of the different species along the two studied transects in the inner cove and at the cove entrance. The distribution of the two species Pseudotachidius jubanyensis and Scottopsyllus (S.) praecipuus was studied in detail; their body volumes are given for developmental stages and adults, and their importance for the total biovolume at the different stations is discussed. Statistical analyses (Spearman rank, canonical correspondence analysis) indicate that the biovolume of harpacticoid copepods was related more to total organic matter than to the carbon:nitrogen ratio and chloroplastic equivalents or even grain size and depth. While P. jubanyensis was strongly connected to depth and to a lesser extent to small grain sizes, S. (S.) praecipuus showed a preference for sites with low chloroplastic equivalent values, but neither of them was related to total organic matter.
The shallow-water Asellota (Crustacea: Isopoda) from the Beagle Channel: Preliminary taxonomic and zoogeographical results
Authors: Lía Doti Brenda , Roccatagliata Daniel , Zelaya Diego Gabriel
Published: October 2008

The shallow-water Asellota from the Beagle Channel were investigated, based on material collected at four localities in 2001-2002. A total of 3,124 asellotes were sorted, and three new species and 12 new records of distribution were reported. The Paramunnidae showed the highest species diversity and abundance (11 species and 1,463 specimens). The present research raises the number of species known from the Beagle Channel to 23; of these, 16 were previously reported from the Magellan Straits, representing 69% of similarity. Based on the present results and published data, the faunistic affinities for the shallow-water Asellota was 30% between the Magellan region and the Scotia Arc, and 26% between the Magellan region and the Antarctic Peninsula.
Distribution, reproductive and energetic conditions of decapod crustaceans along the Scotia Arc (Southern Ocean)
Authors: Lovrich Gustavo A. , Romero M. Carolina , Tapella Federico , Thatje Sven
Published: October 2008

Studies on decapod distribution patterns and reproductive and energetic conditions were carried out along the islands and shallows of the Scotia Arc (Southern Ocean) during the RV “Polarstern” LAMPOS expedition (ANT XIX/5) between April and May 2002. A clear biogeographic zonation was found. The Subantarctic Magellan-South Atlantic decapod fauna consisting of both “natant” (caridean) and “reptant” (astacidean, anomuran, and brachyuran) decapods appeared along the northern branch of the Scotia Arc to South Georgia, where Subantarctic and Antarctic faunas were found overlapping. An impoverished caridean shrimp fauna was found along the islands of the southern branch, from the South Sandwich Islands to the Antarctic Peninsula. Differences in the reproductive traits of the two most abundant species were detected. The reproductive cycle of Notocrangon antarcticus at South Georgia was more advanced than that at the South Orkney Islands, probably due to temperature differences between the two locations. Although the oogenesis and the reproductive cycle of Munida subrugosa seem to be in phase at Burdwood Bank and in the Beagle Channel, the oocyte number is probably lower at the former location. A new index was used to measure the energy devoted to reproduction by relating the energy contents of the egg mass/ovary plus hepatopancreas and the energy content of the whole body. This index revealed that the energy investment in reproduction was (1) independent of the sampling location, (2) species-specific, and (3) larger in caridean shrimps than in galatheid crabs.
On the distribution of decapod crustaceans from the Magellan Biogeographic Province and the Antarctic region
Authors: Boschi Enrique E. , Gavio María A.
Published: October 2008

The distribution of decapod crustaceans in the southernmost areas of South America and the Antarctic is assessed considering the Magellan Biogeographic Province instead of the antiboreal region. Possible associations between decapod crustaceans from the Magellan Biogeographic Province and those from the Antarctic region are analysed. Species records were assigned to seven geographic regions that were clustered using multivariate analyses based on species presence/absence and Bray-Curtis similarity. The results showed two well-established clusters, one of which included the Pacific and Atlantic areas of the Magellan Province, the southern tip of South America and the Kerguelen Arc islands, with the highest similarity between the southern tip and the Atlantic area. Another cluster was well separated and included the Antarctic and South Georgia with the highest similarity index. Earlier studies and results obtained here suggest that the faunas of southern Chile and southern Argentina are biogeographically related. There is a low level of association among decapod species from the circum-Antarctic region and the Magellan Province.
Constraints and trade-offs in climate-dependent adaptation: energy budgets and growth in a latitudinal cline
Authors: Pörtner Hans O. , Storch Daniela , Heilmayer Olaf
Published: October 2008

Characteristics of temperature-dependent metabolic adaptation as well as their implications for associated changes in energy budgets are analysed based on comparisons of fish and invertebrates from various latitudinal clines in northern and southern hemispheres and on integrated ecological and physiological approaches. To identify putative “bottlenecks” of adaptation and for a general cause and effect understanding, the temperature sensitivity of growth as a key energy budget component is investigated, considering underlying processes at population, whole animal and cellular levels. Available data support the hypothesis that natural selection favours individuals for energy efficiency and maximised growth, but is subject to constraints of limited energy availability and temperature. According to emerging relationships between energy turnover, temperature variability and thermal tolerance, the notion that selection should favour a certain metabolic rate according to mean temperature is too simplistic. Within the energy budget, savings in maintenance costs set free energy for growth, visible as growth increments at a low standard metabolic rate. Such energy savings are maximised at the permanently low temperature of the Antarctic. However, some variability persists as pelagic lifestyles in the Antarctic are fuelled by higher metabolic rates at the expense of reduced growth. Temperature variability in the cold, as in the Subarctic, causes a rise in maintenance costs at the expense of growth, but in favour of exercise and thus foraging capacity. Such transitions in energy cost between sub-polar and polar areas are not visible in the southern hemisphere, where there is less temperature variability. However, these patterns—as well as many of the underlying mechanisms—still remain incompletely investigated, especially with respect to the suggested hierarchy in energy allocation to energy budget components.
Somatic energy content and histological analysis of the gonads in Antarctic fish from the Scotia Arc
Authors: Vanella Fabián Alberto , Calvo Jorge , Morriconi Elba Rosa , Aureliano Daniel Ramón
Published: October 2008

Histological characteristics of the gonads and the energy contents of axial muscle, liver and gonads of Antarctic notothenioid fish collected during the LAMPOS (Latin American Polarstern Study) survey in April 2002 were analysed. Ovaries and testes were staged following histological maturity criteria. Oocyte diameters frequency were established and fecundity values were estimated. The energetic values (kJ/g) of different organs were determined using a microcalorimetric bomb. Ovaries of Chaenocephalus aceratus showed a generalised atretic process. The gonadal histology of Champsocephalus gunnari, Pseudochaenichthys georgianus and Chionodracus rastrospinosus suggests that their spawnings take place in autumn. Gobionotothen gibberifrons and Lepidonotothen larseni females were in the process of maturation, with the ovaries of the former containing yolked and atretic oocytes together. Ovaries of Lepidonotothen kempi showed old postovulatory follicles, which provided evidence of previous spawning. Gonads from both sexes of Dissostichus eleginoides were immature. Absolute and relative fecundity were lower in Channichthyidae than in Nototheniidae. The energy contents of the different organs analysed were: liver > gonads > axial muscle. The highest energy density value (kJ/g wet body mass) was found in Dissostichus eleginoides.
Influence of temperature, habitat and body mass on routine metabolic rates of Subantarctic teleosts
Authors: Vanella Fabián Alberto , Calvo Jorge
Published: October 2008

Subantarctic notothenioids are exposed to wider variations in temperature than those encountered in the Antarctic Ocean, the ancestral environment of the group. In this study the influence of temperature on the routine metabolic rate of Subantarctic teleosts was described and the results were compared with routine metabolic rates of species with different geographical distributions, exploring the concept of Metabolic Cold Adaptation (MCA). Oxygen consumption (VO2R) was determined as an estimate of the routine metabolic rate for the following Subantarctic notothenioids: Paranotothenia magellanica, Patagonotothen sima, Eleginops maclovinus, Harpagifer bispinis and the eelpout Austrolycus depressiceps. In all studied species and tested temperatures, body mass and VO2R showed a positive correlation. A drop in the temperature from 10 to 2°C produced a significant reduction of VO2R values with a Q10 (10-2) varying between 4.69 and 9.54. VO2R values were related to species habitat: pelagic species reached the highest values of VO2R, while sluggish species had the lowest ones. We can conclude that the metabolic rates of these species of Subantarctic fish do not show MCA at the investigated temperatures.
Muscle growth in Antarctic and Subantarctic notothenioid fishes
Authors: Fernández Daniel Alfredo , Calvo Jorge , Johnston Ian Alistair
Published: October 2008

The suborder Notothenioidei comprises 122 species divided into 8 families, with members of 6 of the families living outside Antarctic waters. The Antarctic species underwent an extensive radiation from a small demersal ancestor to occupy different ecological niches and levels in the water column. The axial muscle of Antarctic and some Subantarctic notothenioids is unusual in containing very large diameter muscle fibres and a low muscle fibre number. Maximum fibre diameters are greater than 500 mm in many species. There is no indication of systematic differences in fibre number, fibre type composition, ATPase activity, time of cessation of fibre recruitment (hyperplasia) and swimming performance between Antarctic and Subantarctic species. Instead, fibre number is significantly decreased in species belonging to the most derived families relative to the more basal families (a trend that also correlates with an increase in the diameter of the fibres). The length of the cell cycle of the muscle fibres shows cold compensation in the Antarctic species H. antarcticus relative to the closely related Subantarctic one (H. bispinis). Feeding after a starvation period results in a strong stimulation of the proliferation of muscle fiber progenitors in H. bispinis. Similar studies have not yet been performed on any Antarctic species.