bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallel, paedomorphic evolutionary processes of the bivalve-inhabiting hydrozoans (Leptomedusae, Eirenidae) deduced from the morphology, life cycle and biogeography, with special reference to taxonomic treatment of Eugymnanthea
Authors: Kubota Shin
Published: October 2008

It is hypothesized that bivalve-inhabiting hydroids originated from colonial, free-living eirenid hydrozoans, initially appearing as an Eutima species with solitary hydroids producing immature medusae with tentacles and manubrium, and also with derived characteristics of the marginal warts of the mature medusae as the remnants of the tentacular bulbs of the ancestral eirenid, and decreased number of statocysts. The derivate eumedusoid-producing Eugymnanthea evolved then. Deduced from the morphology, life cycles, and geographical distributions of this group and of all the known extant Eutima species, it is proposed that parallel, paedomorphic evolution took place in the marginal regions of the area of distribution of the ancestral-like Eutima at least in the northern hemisphere of both the Pacific and the Atlantic Oceans. Eugymnanthea appeared as a polyphyletic taxon as a result of the parallel evolution of different species of Eutima. It is pointed out that Eugymnanthea and Eutima are to be merged into a single genus in the future.
Deep-water Hydromedusae from the Lacaze-Duthiers submarine canyon (Banyuls, northwestern Mediterranean) and description of two new genera, Guillea and Parateclaia
Authors: Bouillon J. , Pagès F. , Gili J. M. , Palanques A. , Puig P. , Heussner S.
Published: October 2008

Several species of hydromedusae are reported from material collected by sediment traps placed in the Lacaze-Duthiers submarine canyon, off Banyuls (north-western Mediterranean). Two new taxa Guillea canyonincolae gen. nov. et sp. nov. and Parateclaia euromarge fam. nov., gen. nov. et sp. nov., are described. The existence of highly-specific hydromedusa populations in other Mediterranean canyons which appear to be related via geological history, topography, hydrographic and ecological features peculiar to each canyon, is discussed in relation to these new records.
On the homogeneity of the wave field in coastal areas as determined from ERS-2 and RADARSAT synthetic aperture radar images of the ocean surface
Authors: Ocampo-Torres F. J.
Published: October 2008

Spatial variations of the wave field in coastal waters were determined from images obtained by synthetic aperture radar (SAR) on board the European satellites ERS-1 and 2. The capabilities of RADARSAT SAR to provide useful information for evaluating the wave field variation in nearshore waters are explored. Besides the different polarization between ERS and RADARSAT SARs, range to velocity ratios, signal to noise ratios and the acquisition swath are important issues to take into consideration in comparing the performance of the radar systems. In situ data from a coastal region in the north-west of Baja California are used to validate some of the remote observations and to provide relevant ground truth. Particular aspects of wave phenomena in finite depth waters such as refraction, diffraction and groupiness are considered. An appropriate method for analysing the radar images is applied to describe wave features as they originate from a non-homogeneous process. Wave field characteristics and their spatial variations as resolved by RADARSAT SAR are relevant variables for applications such as beach erosion and coastal management. Inclusion of specific modules to retrieve this type of information should be considered for operational software packages for the use and application of ocean surface data from SAR images. The differences of the two radar systems did not affect their capabilities to observe the wave field in coastal regions.
Seasonal variability of the upper warmwatersphere in the Canary Basin
Authors: Ratsimandresy A. W. , Pelegrí J. L. , Marrero-Díaz A. , Hernández-Guerra A. , Martínez A.
Published: October 2008

Two years of periodic XBT data, along seven transects covering the Canary Basin, were examined to analyse the seasonal cycle of the upper layers of the warmwatersphere. This is characterised by seasonal storage/release of heat in the surface mixed layer and by the winter formation of a subsurface positive temperature anomaly. Its maximum value takes place in early winter and deepens to about 150 m in late spring, disappearing afterwards. We present a very simple argument, which illustrates how the evolution of the temperature anomaly is controlled both by the ocean-atmosphere heat exchange and by the shape of the North-Atlantic Central Water T-S relationship.
On the relevance of diapycnal mixing for the stability of frontal meanders
Authors: Rodríguez-Santana A. , Pelegrí J. L. , Sangrà P. , Marrero-Díaz A.
Published: October 2008

This work examines the possible importance of shear-induced diapycnal mixing in controlling the evolution and stability of meanders in oceanic frontal jets. We first review the conditions necessary for vortex stability and investigate how these may be modified in the presence of diapycnal mixing. The procedure used is rather crude but provides a measure of the relative importance of diapycnal mixing. It consists in constructing a simplified equation for the radial velocity that retains the density tendency and examining under what circumstances this velocity may grow in time. Next, we use a simple two-dimensional isopycnic model to examine the intensity of diapycnal mixing in meanders. In the model the along-front velocity is in geostrophic balance and the ageostrophic contributions are an oscillating deformation field and diapycnal mass exchange. The horizontal deformation field increases the slope of the isopycnals in temporal scales typical of Gulf Stream meanders, causing a reduction of the gradient Richardson number, Ri. The diapycnal flux is calculated as the divergence of the density Reynolds flux, which is parameterized in terms of Ri. The results of the model show that diapycnal mixing increases during the frontogenetical stages, reaching density tendency values of the order of 10-4 kg m-3s-1 and convergence/divergence values of the order of 10-3 s-1. It turns out that diapycnal mixing in meanders may be intense enough to control the separation and slope of the isopycnals and to condition the possibility of barotropic instability.
Vertical velocities at an ocean front
Authors: Vélez-Belchí Pedro , Tintoré Joaquín
Published: October 2008

Simple scaling arguments conclude that the dominant motions in the ocean are horizontal. However, the vertical velocity plays a crucial role, connecting the active upper layer with the deep ocean. Vertical velocities are mostly associated with the existence of non-transient atmospheric wind forcing or with the presence of mesoscale features. The former are the well known upwelling areas, usually found at the eastern side of the oceans and characterised by upward vertical velocities. The latter have been observed more recently in a number of areas of the world´s oceans, where the vertical velocity has been found to be of the order of several tens of meters per day, that is, an order of magnitude higher than the largest vertical velocity usually observed in upwelling areas. Nevertheless, at present, vertical velocities cannot be measured and indirect methods are therefore needed to estimate them. In this paper, the vertical velocity field is inferred via the quasi-geostrophic omega equation, using density data from a quasi-permanent upper ocean front located at the northern part of the western Alborán gyre.
The ocean, our climate and the earth's health
Authors: Pelegrí J. L. , Alonso I. , Arístegui J.
Published: October 2008

The ocean is the major element controlling the long-term stability of the earth´s climate. It involves a complex pattern of interrelations between its physical, geological, chemical and biological components: the greater the complexity and diversity of these links the more robust is the stability of the system, and the healthier the earth. A set of papers that resulted from communications presented at a workshop held in Las Palmas on November 1998 emphasises the need for an interdisciplinary approach to the ocean.
Larval trophodynamics, turbulence, and drift on Georges Bank: A sensitivity analysis of Cod and Haddock
Authors: Werner Francisco E. , MacKenzie Brian R. , Perry R. Ian , Lough R. Gregory , Naimie Christopher E. , Blaton Brian O. , Quinlan John A.
Published: October 2008

Using an individual-based model approach we consider trophodynamic effects on the growth and survival of larval cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank during late winter/early spring. These studies represent an extension of results described in Werner et al. (1996; Deep-Sea Res. II), wherein the effect of turbulence-enhanced larval-prey contact rates increased the effective prey concentration resulting in growth of cod larvae consistent with observed rates in the field. We reformulated the feeding of the larvae to include existing relationships between maximum prey-length and larval-length and we examined: (i) larval search behaviour and its effect on encounter with prey, (ii) the ability of larvae to pursue and capture prey in a turbulent environment, and (iii) the effect of turbulence on the dispersion of larvae in the vertical. We find that search behaviour, the effect of turbulence on pursuit and capture, and vertical dispersion decrease the predicted larval growth rates compared to those observed in the earlier study. These results suggest that larval feeding behaviour, and especially the ability of larvae to pursue encountered prey, could be an important input to larval growth and survival models. The inclusion of turbulence in determining the position of passive larvae in the water column allows the larvae to sample the entire water column, contributing to a decrease in the variance of the size of the larvae over time. The ability of larvae to swim and aggregate in the vertical will be necessary to reproduce distributions observed in the field.
Gaia and the Mediterranean Sea
Authors: Hsü Kenneth J.
Published: October 2008

The Earth is a self-organizing system liking a living organism. Lovelock proposed Gaia as a metaphor to designate the check and balance ofterrestrial temperatures: the Earth is never too hot so that the ocean could boil, and the Earth is never too cold that the ocean could freeze from top to bottom. Hsü proposed that Gaia is endothermic because the life on Earth has been alternate successions of air-conditioners and heaters which evolved and deactivate or reinforce the terrestial greenhouse of carbon dioxide in atmosphere. When Earth was heating up too much, the air-conditioneers, such as anaerobic bacteria, cyanobacteria, skeletal organisms and trees, and finally calcareous plankton, went to work to bring the terrestrial temperature down. When the Earth was freezing at times of continental glaciation, heaters went to work, such as methanogenic bacteria, Ediacaran faunas, tundra and desert plants, and now Homo sapiens. Gaia has to have other organs to keep the self-organizing system vital. This paper presents a postulate that the Miocene Mediterranean Sea acted as Gaia´s kidney. The steady influx of dissolved ions and debris into the ocean causes inevitable increase of ocean´s salinity. The fossil and geochemicl records indicate that the ocean has never been too saline nor too brackish for the survival of normal marine organisms: the salinity ranged from about 32 to 36 pro mil during the last billion years. Ocean-drilling cruises to the Mediterranean discovered a very large salt formation, deposited during some 5 million years ago when the Mediterranean dried up. A study of the geochemical balance of the oceans indicates that the deposition of very large salt bodies in isolated basins such as the Miocene Mediterranean every 100 million years or so. The saline giants have the function of Gaia´s kidney. With periodical removals of the salt ions and the heavy metals from seawater, the world´s ocean have been rendered forever habitable. Gaia has to have a kidney. The desiccation of the Mediterranean is the evidence of a functioning kidney. Earlier kidney functions were performed during the deposition of the Cretaceous (South Atlantic), Jurassic (Gulf of Mexico), Permo-Triassic (Europe), Devonian (Canada),.Cambrian/Precambrian (Gondwana) saline giants.
Sources and fates of silicon in the ocean: the role of diatoms in the climate and glacial cycles
Authors: Dugdale R. C. , Wilkerson F. P.
Published: October 2008

Diatoms with their fast growth rates and obligate requirement for Si have a unique relationship to the oceanic Si cycle with the potential for controlling the nutrient and CO2 environment of large important areas of the ocean. The new production of diatoms based on both new nitrogen and Si sources is described using a Si-pump based upon the differential regeneration of the two elements. This approach, applied to the eastern equatorial Pacific, showed diatoms to respond as in a Si-limited chemostat, to the low source Si(OH)4 in the Equatorial UnderCurrent. Increased Si(OH)4 results in increased diatom productivity, suppression of non-diatom populations and decreased surface pCO2. The deficiency in source concentrations of Si(OH)4 results from low Si(OH)4:NO3 water originating in the vicinity of the Antarctic Polar Front, a consequence of the extraordinary trapping of Si by the Southern Ocean. In glacial periods this trapping is reduced several fold and likely results in increased Si(OH)4 export to the north, and increased Si(OH)4 production and deposition at the equatorial Pacific which can be expected to reduce surface pCO2. The connections between the eastern equatorial Pacific export production and Southern Ocean Si trapping may provide a major biogeochemical feedback system with implications for contemporary and paleoclimatology.
Thermohaline feedback loops and Natural Capital
Authors: Sawyer Hopkins Tom
Published: October 2008

Human interference now represents an inextricable component of all major ecosystems. Whether this is through top-down overharvesting of ecosystem production or bottom-up alteration (deliberate or inadvertent) of the abiotic conditions, the planet´s ecosphere is in a vicious degradation cycle. For our economy to shift from exploiting to sustaining the natural systems, the solution, if there is to be one, will involve incorporation of the value of natural capital into the economic and political feedback loop. For the science sector, this will involve developing methodologies to evaluate the nonlinear and behavioral dynamics of entire systems in ways that can be coupled with economic models. One essential characteristic of systems science involves the interactions between internal components and external systems. Thermohaline circulations and their feedback loops illustrate a class of such interactive pathways. Examples from the Arctic, Mediterranean, and the US East Coast along with some of their associated ecological impacts are reviewed. Understanding how thermohaline interactions provide stability to the marine biotic environment and under what conditions this stability could be destabilized is a fundamental step toward evaluating the non-linear response of marine systems to anthropogenic stress.
The sedimentary record of dinoflagellate cysts: looking back into the future of phytoplankton blooms
Authors: Dale Barrie
Published: October 2008

Marine systems are not as well understood as terrestrial systems, and there is still a great need for more primary observations, in the tradition of the old-time naturalists, before newer methods such as molecular genetics and modeling can be fully utilized. The scientific process whereby the smaller, detailed building blocks of observation are ultimately linked towards better understanding natural systems is illustrated from my own career experience, especially with regard to the dinoflagellates and plankton blooms. Some dinoflagellates produce a fossilizable resting stage (cyst) in their life cycle, and dinoflagellate cysts have become one of the most important groups of microfossils used in geological exploration (e.g. oil and gas). This has stimulated both paleontological and biological research producing detailed building blocks of information, currently scattered throughout the respective literature. Here, I attempt to bring together the present day perspective, from biology, with the past, from paleontology, as the most comprehensive basis for future work on the group. This shows the cysts to be the critical link needed for focusing future molecular genetics studies towards a more verifiable view of evolutionary pathways, and it also suggests new integrated methods for studying past, present, and future blooms. The large, rapidly growing field of harmful algal bloom studies is producing many different building blocks, but plankton blooms as episodic phenomena are still poorly understood. This is largely due to the general lack of long-term datasets allowing identification of the changing environmental factors that permit certain species to bloom at unpredictable intervals of time. Cysts in sediments are useful environmental indicators today, e.g. reflecting aspects of climate and pollution, and provide information directly relevant to some dinoflagellate blooms. They therefore may be used for obtaining retrospective information from the sedimentary record on the history of blooms, in turn suggesting information relevant for future blooms and the way we study them.
A case for tolerance in marine ecology: let us not put out the baby with the bathwater
Authors: Arntz Wolf E. , Gili Josep-Maria
Published: October 2008

After working in marine ecological research and lecturing at universities for several decades, the authors are aware that almost none of the concepts and paradigms established at the time they were students or in the decades before have survived unchanged up to the present day. This appears quite natural taking into account the enormous progress made by marine science due to refined methods, extended range of research e.g. into the deep sea and the polar regions, increased number of researchers and funding, and greatly improved and accelerated exchange of scientific results. What is striking, however, against this background is the almost messianic fervour with which many of our professional guild (and not only the younger ones lacking experience) call for the immediate “abolishment” or “dismissal” of old ideas because their creators were wrong in thinking the way they did. In these authors` opinion, there is a basic misunderstandig about the role of ecological concepts in scientific argumentation. Very few concepts are so foolish that they can be dismissed entirely without any loss; the vast majority contain some truth that may fit at least certain situations, and may thus serve as a brickstone in constructing ecological theory. An attempt will be made to expand on that point in this contribution. What is more important: many of the concepts nowadays considered (partially?) erroneous have stimulated scientific discussion enormously, in some cases up to the present day and have, by their mere existence, guaranteed that ecological work was found necessary to continue in the respective fields. Finally, observing the tremendous pace at which ecological progress is being made these days in some disciplines and at the same time, the degree of uncertainty we are - despite all efforts - still facing in others, it is not difficult to anticipate that many of the new ideas replacing the old concepts nowadays will end up shortly on the garbage dump of science history as well. So tolerance should be the motto: let us not put out the baby with the bathwater! Give the old concepts their credit, look eagerly for alternatives and try to provide the best possible evidence for your results, but be modest. There may be various solutions to one ecological problem, and the way to handle this situation is differentiation, not abolishment.
Marine diversity: the paradigms in patterns of species richness examined
Authors: Gray John S.
Published: October 2008

The two central paradigms of marine diversity are that there is a latitudinal cline of increasing species richness from poles to tropics and that species richness increases with depth to a maximum around 2,000 m and thereafter decreases. However, these paradigms were based on data collected in the late 1950´s and early 1960´s. Here I show that the 1960´s data, are not representative and thus the paradigms need re-examination. New data from coastal areas in the northern hemisphere record species richness as high as the highest recorded in the deep-sea. Whilst this suggests that the cline of increasing diversity from shallow to deep-sea does not exist, however, the database for the deep sea is not sufficient to draw such a conclusion. The basic problem with the data from the 1960s is that samples were taken on ecological scales and yet they are used to answer evolutionary questions. The questions that such data were to answer were why do the tropics have higher species richness than polar regions or why do deep-sea sediments have more species than coastal sediments? Evolutionary questions need data from much larger spatial areas. Recently, data representative of large scales have been collected from coastal areas in the northern hemisphere and show that there is a cline of increasing species richness from the Arctic to the tropics, but there does not yet seem to be a similar cline in the southern hemisphere. A number of hypotheses have been proposed for the observed patterns in biodiversity. In terrestrial ecology the energy-productivity hypothesis has gained wide acceptance as an explanation for the latitudinal gradient. Here I examine this and other hypotheses critically. Finally an analysis of research priorities is made. Assessment is urgently needed of the spatial scales and dynamics of species richness from point samples to assemblages, habitats and landscapes, especially in coastal areas and in the tropics, where the threats to biodiversity are greatest. New technologies are available, such as side-scan sonar, acoustics, and under-water digital video cameras but as yet have been relatively little used. Conservation of marine biodiversity must be based on sound theory, yet marine diversity studies lag well behind those of terrestrial habitats.
Formation and fate of marine snow: small-scale processes with large- scale implications
Authors: Kiørboe Thomas
Published: October 2008

Marine snow aggregates are believed to be the main vehicles for vertical material transport in the ocean. However, aggregates are also sites of elevated heterotrophic activity, which may rather cause enhanced retention of aggregated material in the upper ocean. Small-scale biological-physical interactions govern the formation and fate of marine snow. Aggregates may form by physical coagulation: fluid motion causes collisions between small primary particles (e.g. phytoplankton) that may then stick together to form aggregates with enhanced sinking velocities. Bacteria may subsequently solubilise and remineralise aggregated particles. Because the solubilization rate exceeds the remineralization rate, organic solutes leak out of sinking aggregates. The leaking solutes spread by diffusion and advection and form a chemical trail in the wake of the sinking aggregate that may guide small zooplankters to the aggregate. Also, suspended bacteria may enjoy the elevated concentration of organic solutes in the plume. I explore these small-scale formation and degradation processes by means of models, experiments and field observations. The larger scale implications for the structure and functioning of pelagic food chains of export vs. retention of material will be discussed.
MEDITS-based information on the deep water red shrimps Aristaeomorpha foliacea and Aristeus antennatus (Crustacea: Decapoda: Aristeidae)
Authors: Cau Angelo , Carbonell Aina , Follesa Maria Cristina , Mannini Alessandro , Orsi Relini Lidia , Politou Chrissi Yianna , Ragonese Sergio , Rinelli Paola
Published: October 2008

The application of statistical models on a time series of data arising from the MEDITS International Trawl Survey, an experimental demersal resources survey carried out during six years (1994-1999) in the same season of the year (late spring - early summer) using the same fishing gear in a large part of the Mediterranean, has allowed for a study to compare, for the first time, the space-time distribution, abundance, and size structure of the two Aristeids Aristaeomorpha foliacea and Aristeus antennatus throughout most of the Mediterranean Sea. This research has shown a large variability among the six reference areas, that were arbitrarily defined within the basin. In particular the two shrimps do not seem to present any correlation or yield continuity in the years. The same lack of homogeneity was also observed in the time trend of the abundances and frequencies of each of the two species. These data seem to confirm the intrinsic variability of the species, the cause of which is still unknown and undocumented. Nevertheless, a longitudinal gradient of catches has been observed where A. antennatus is more abundant in the west and A. foliacea in the east of the basin.
Biogeography of epibenthic crustaceans on the shelf and upper slope off the Iberian Peninsula Mediterranean coasts: implications for the establishment of natural management areas
Authors: Abelló Pere , Carbonell Aina , Torres Pedro
Published: October 2008

The patterns of occurrence and bathymetric distribution of epibenthic crustaceans on the continental shelf and upper slope down to a depth of 800 m are analysed based on data gathered during six demersal trawl surveys performed annually in spring along the Mediterranean coasts of the Iberian Peninsula (from the Straits of Gibraltar to Cape Creus) between 1994 and 1999. A total of 598 valid hauls has been studied providing a total of 108 species of decapods, two stomatopods, one euphausiid, one mysid and one isopod. The study area has been subdivided into seven sectors according to their geomorphological characteristics, and the patterns of occurrence and abundance by depth have been analysed separately for each of the sectors. Detailed data on bathymetric distribution are presented for each species. Two main biogeographical areas can be discerned along the study area, which can approximately be separated at Palos Cape: the Alborán Sea to the southwest, and the northwestern Mediterranean (Levantine and Catalan Seas) northwest of Palos Cape. The continental shelf in the Alborán Sea (the most western area of the Mediterranean) is extremely narrow whereas it is much wider in the northwestern Mediterranean. The influence of Atlantic waters entering the Mediterranean is particularly strong in the Alborán Sea which shows a particularly high species richness of Atlantic affinity. Within the context of the western Mediterranean Sea, the Alborán Sea region shows important faunistic characteristics such that it might be considered as a possible separate natural management area for demersal fisheries.
Cephalopod assemblages caught by trawling along the Iberian Peninsula mediterranean coast
Authors: González María , Sánchez Pilar
Published: October 2008

The cephalopod fauna collected in five MEDITS-ES trawl surveys carried out on the Iberian Mediterranean coast was analysed. Hauls, which were carried out in spring between 1994 and 1998, numbered 480. A total of 34 cephalopod species, grouped in 11 families, was found at depths of between 25 and 786 m. Species and samples assemblages were analysed with the Bray-Curtis similarity index. From the physical parameters studied (depth, temperature and bottom type) only depth showed a positive correlation with cephalopod distribution. Three main cephalopod communities were defined: the shelf community (< 150 m), the middle slope community (> 480 m) and a group of cephalopods which were widely distributed more abundantly on the lower continental shelf-upper slope (150-480 m). SIMPER analysis revealed that Loligo (Alloteuthis) media was the main indicator species of the shelf group, Eledone cirrhosa was the indicator species of the lower shelf upper slope group and Todarodes sagittatus of the middle slope community. The 150-480 m stratum was considered a transitional zone, representing an overlapping region for shelf and slope faunas.
A procedure to evaluate the effect of lag-time in studying length structure and growth rate of young fish: the case of Phycis blennoides Brunnich, 1768 (Osteichthyes: Gadiformes) in the Central Mediterranean
Authors: Ragonese Sergio , Fiorentino Fabio , Rinelli Paola , Greco Silvestro
Published: October 2008

The joint analysis of data from different programs represents a good opportunity to improve knowledge about the condition of any exploited populations. This note investigates the influence of lag-time in sample characteristics (growth rate and recruitment) by following a simple and quick exploratory procedure. In order to illustrate this approach, the Greater Fork-beard (Phycis blennoides Brunnich, 1768), a species with discrete recruitment pattern and available to the capture process in the first years of life, was considered . The length-frequency distributions (LFD), obtained during five spring (MEDITS - International) and successive autumn (GRUND - Italian) bottom trawl surveys, conducted from 1994 to 1998, in the Strait of Sicily and Southern Tyrrhenian Sea (Mediterranean) were analysed. The procedure was divided into three steps. Firstly, the LFD were analysed in order to estimate the mean length of the first component in each survey. Secondly, for each survey, the difference between the standardized mean lengths of the first components in the LFD of the two areas was compared with the corresponding lag-time in order to assess any systematic temporal effect in recruitment periodicity. Thirdly, for each area, the absolute and instantaneous growth rates between the spring and autumn surveys of the same year were computed on the base of the lag-time, to evaluate any difference in growth rate between the areas. The results show that the earlier the surveys begin in the Strait of Sicily, the smaller is the difference in mean length. Since the growth rates between the two areas are practically indistinguishable, the higher mean lengths observed in samples from the Strait of Sicily mainly reflect the lag-time. The reference mean growth rate found (1.03 and 0.93 cm per month in the Strait of Sicily and Southern Tyrrhenian Sea, respectively) agreed with the literature. In spring, the recruits of 0 group represent up to 90% of the whole trawl catch, and the smallest length class observed (4.5-5.0 cm) is close to the size of transition from the pelagic to the demersal one. The proposed exploratory procedure shows that systematic differences between the two investigated sub-areas in mean size and growth rate suggested by actual data are strongly reduced after having included the lag-time in the analysis.
APPENDIXES. Appendix 1. List of scientists involved in cruises and data generation and elaboration Appendix 2. List of published articles based on MEDITS-generated data and material
Authors: Abelló P. , Bertrand J. A. , Gil de Sola L. , Papaconstantinou C. , Relini G. , Souplet A.
Published: October 2008

Not available
Distribution of Mullus barbatus and M. surmuletus (Osteichthyes: Perciformes) in the Mediterranean continental shelf: implications for management
Authors: Tserpes George , Fiorentino Fabio , Levi Dino , Cau Angelo , Murenu Matteo , Zamboni Ada , Papaconstantinou Costas
Published: October 2008

The present work attempts to study the spatio-temporal distribution of Mullus barbatus and M. surmuletus in the Mediterranean Sea by using a time series of data from an international bottom trawl survey that covered a wide area of the Mediterranean Sea. The experimental surveys were accomplished annually from 1994 to 2000 on approximately 1000 pre-defined sampling stations distributed in 15 major areas. Selection of stations was based on a depth-stratified random sampling scheme that included five depth strata: 10-50, 50-100, 100-200, 200-500 and 500-800 m. The examined species were found throughout the studied region, mostly in depths down to 200 m. Abundance differences among major areas were found to be statistically significant and were attributed to the different exploitation patterns, as well as the different abiotic and biotic conditions prevailing in each area. Although both species undergo high fishing pressure, results did not demonstrate any decreasing trends in their abundance indices suggesting the existence of a good stock-recruitment relationship over the studied period. However, the dominance of young fish that has been found, makes the stocks highly vulnerable to recruitment changes; hence protection of spawning and nursery areas seems to be essential for their conservation.
Scientific knowledge of biological processes potentially useful in fish stock predictions
Authors: Köster Friedrich W. , Schnack Dietrich , Möllmann Christian
Published: October 2008

Based on an extensive review of available knowledge, several sources of information have been identified as potentially useful in fish stock predictions. They refer to a variety of biological processes of importance for stock dynamics, e.g. growth, maturation and egg production as well as early and juvenile life stage survival and subsequent recruitment, for which examples are given. Environmental variables impacting these processes were derived, ranging from simple statistical exploratory analyses to complex process studies for various stocks in different sea areas. Causal relationships are understood to varying degrees and in several cases the identified variables may only be taken as proxies for processes not investigated in detail yet. Besides the explanatory power of relevant variables, their predictability and related predictive time frames are of major importance for a potential application in stock predictions. These criteria in particular may hamper implementation in the foreseeable future in several cases. However, the information may still be highly relevant for a) hindcasting stock developments that are so far not fully understood, b) defining stock projection scenarios for simulation of different fishery management strategies under varying environmental conditions and considering species interactions and c) elucidating areas of future research to further enhance our predictive capabilities.
Recruitment of Baltic cod and sprat stocks: identification of critical life stages and incorporation of environmental variability into stock-recruitment relationships
Authors: Köster Friedrich W. , Hinrichsen Hans-Harald , Schnack Dietrich , John Mike A. St. , Mackenzie Brian R. , Tomkiewicz Jonna , Möllmann Christian , Kraus Gerd , Plikshs Maris , Makarchouk Andrej , Aro Eeri
Published: October 2008

The recruitment processes of Baltic cod and sprat were analysed and critical periods were identified by addressing the major impact factors on individual early life history stages separately and relating observed abundance data between successive stages. For cod, recruitment appeared to be dependent on egg survival, with low oxygen concentration in dwelling depths and predation by clupeids as the major causes for egg mortality. Surviving egg production and larval abundance were weakly correlated, whereas larval abundance was significantly related to year class strength. This indicated that the period between the late egg and the early larval stage is critical for cod recruitment. A potential variable identified to affect this life stage was prey availability for larvae. For sprat, early and late egg stage production as well as late egg stage production and larval abundance were significantly related. However, year class strength was largely independent of larval abundance. Thus, the period between the late larval and early juvenile stage appeared to be critical for sprat recruitment. Potential variables identified to affect this life stage were ambient temperature and wind stress. Environmental factors showing statistically significant covariance with the survival of one of these critical life stages were incorporated into stock-recruitment models for individual spawning areas separately and for the Central Baltic combined.
Comparing survey and assessment data: Consequences for stock evaluation of Northeast Arctic Greenland halibut
Authors: Thomas Albert Ole , Høines Åge S.
Published: October 2008

Based on VPA-estimates of abundance, survey data and commercial catch statistics of Northeast Arctic Greenland halibut (Reinhardtius hippoglossoides Walbaum), the paper describes trends by year-class and age in the distribution of Greenland halibut between surveyed and not-surveyed areas. Changes in the distribution of I-group around 1990 to areas beyond the Svalbard surveys has previously been described and related to temperature changes in the Spitsbergen Current. This paper shows that this displaced distribution of the 1989-94 year-classes persisted up to age 7. The results indicate that the displacement was an extraordinary situation and other similar distribution shifts have not occurred during the last 30 years or more. Further, the shift co-occurred with extreme levels of the 137 year long time series of the index of the North-Atlantic Oscillation (NAO). The results are discussed in relation to stock management and climate change.
Early estimates of recruitment of the Belt Sea cod stock
Authors: Oeberst Rainer , Bleil Martina
Published: October 2008

The Belt Sea cod stock produced very different year class abundances from 1993 to 1999. After the strong year class 1994 a poor year class 1995 followed. Stronger year classes were observed again in 1996 and in 1997. Comparative analyses of the maturity development of female cods, of the fecundity and of the year class abundance demonstrated the following: The maturity development of female cods from November to March was very different in the years investigated. However, the analyses showed that an early or late beginning of the maturity development did not give any indications concerning the new year class abundance. The year class strength of Belt Sea cod is mainly determined by the portions of female cod having a maturity stage of more than II at the beginning of the main spawning season in March. A trawl survey during the beginning of the spawning season for estimating the portions of active female spawners can be used for assessing the actual potential population fecundity and arriving at a first estimate of the new year class abundance with acceptable accuracy. These data are available before the spawning season of the Belt Sea cod is finished. The large variations of the portions of active female spawners are influenced by the abundance and the spatial distribution of the main prey component age group 1 herring and by the temperature conditions during the prespawning period.
On the prediction of short term changes in the recruitment of North Sea cod (Gadus morhua) using statistical temperature forecasts
Authors: Planque Benjamin , Fox Clive J. , Saunders Mark A. , Rockett Paul
Published: October 2008

Empirical evidence supports the hypothesis of a general relationship between sea temperature and recruitment of cod stocks across the North Atlantic, as well as between recruitment and the size of the spawning population. In the North Sea, cod year-class strength is inversely related to sea surface temperature during the first half of the year. This stock is currently at a low level, and the future trajectory of the stock biomass will be strongly influenced by recruitment levels. In the present study we investigate the possible use of observed and modelled sea surface temperature (SST) to increase the accuracy and/or time horizon of recruitment forecasts for this stock. We show that the statistical model developed for forecasting spring temperature has good skill (35% skill, with a standard error of 0.36°C) when predictions are made in late January. Within the frame of the current fish stock assessment working group we incorporate SST observations and January forecasts and simulate short-term recruitment projections. The resulting model accounts for a greater fraction of the variance in recruitment (42%) than that obtained without temperature (17%). In operational mode, the model allows forecasting 1.5 years in advance but the accuracy of predicted recruitment remains low. This example indicates that we have not yet reached a point where environmental information can be used with great benefit for the management of North Sea cod. However, a similar strategy may yield greater benefits if developed for other stocks for which environmental effects are better understood and/or account for a larger fraction of the variability in recruitment, for species with a shorter generation time and species for which recruitment forecast is critical to management (e.g. anchovy), and in areas where environmental prediction capabilities may be greater either in accuracy or in lead time.
Physical influences on the stock dynamics of plaice and sole in the North Sea
Authors: Wegner Gerd , Damm Ulrich , Purps Martin
Published: October 2008

A review of the literature on influences of physical factors on plaice and sole stresses the prominent role of water temperature in all life stages of the species. For plaice, e.g., water temperatures on the spawning grounds are inversely correlated with year-class strength, and growth depends primarily on temperatures. In many instances, however, direct and indirect effects are hard to disentangle and to quantify for use in models, e.g. for stock assessment and prediction (SAP). Hydrodynamic circulation influences the egg and larvae distributions. Existing models reveal the drift variability to be of the same magnitude as year to year variations of larval abundance just before immigration. An improved modelling of the processes could combine recent circulation and transport models incorporating physical/biological properties of the eggs and larvae. It is suggested that future research focuses on this approach. The course of irradiation during spring and its influence on mortality of the 0-groups of both species in the nursery deserves further studies if it is to be useful for SAP.
Embedding sea surface temperature anomalies into the stock recruitment relationship of red mullet (Mullus barbatus L. 1758) in the Strait of Sicily
Authors: Levi D. , Andreoli M. G. , Bonanno A. , Fiorentino F. , Garofalo G. , Mazzola S. , Norrito G. , Patti B. , Pernice G. , Ragonese S. , Giusto G. B. , Rizzo P.
Published: October 2008

In the Strait of Sicily, red mullet (Mullus barbatus L. 1758) is one of the most important resources for the bottom trawlers exploiting the shelf fishing grounds. At present, the younger age groups (groups 0-1) represent most of the catches. In order to give more effective advice for fisheries management in the area, this paper is aimed at further investigating the stock-recruitment relationship for red mullet by including environmental information. Indices of the mean abundance of red mullet older than 1 year (spawners) and younger (recruits) were obtained from autumn trawl survey samples by analyzing the length-frequency distributions. Sea surface temperature (SST), expressed as the average monthly anomalies over the period from May to September (referring to 1961-90 climatology), was considered as a proxy for oceanographic processes affecting recruitment. An exploratory analysis was performed using three stock-recruitment relationships (Cushing, Ricker and Beverton-Holt), with and without the effect of SST. The best fit (R2=0.80) was obtained with a Ricker modified curve (lnR = ln(70.17113) + lnS - 0.063812S + 0.060544(S ⋅ E)), including SST anomalies in July and August as a masking factor. Results showed that, for a given spawning stock level, higher recruitment levels corresponded to warmer than average SST in early life stages.
Trends in various biological parameters of the European sardine, Sardina pilchardus (Walbaum, 1792), in the Eastern Mediterranean Sea
Authors: Voulgaridou Pinelopi , Stergiou Konstantinos I.
Published: October 2008

In this study we present the longest time series available concerning various biological parameters of sardine in Greek waters. Biweekly samples were collected within a single day in clusters from random collections of the total landed catch derived from different vessels operating in the Northwest Aegean Sea, between July 1996 and June 2000. Total length (TL) was measured for 51.246 individuals. In addition, for a sub-sample of 50 individuals per sampling period, gross body weight and gonad weight were also measured to the nearest 0.1 and 0.01 g respectively. The analysis of the biweekly length-frequencies showed that the dominant length classes ranged between 130 and 160 mm TL. The mean biweekly TL decreased significantly (r=-0.525, P
Modelling and forecasting monthly swordfish catches in the Eastern Mediterranean
Authors: Stergiou Konstantinos I. , Tserpes George , Peristeraki Panagiota
Published: October 2008

In this study, we used the X-11 census technique for modelling and forecasting the monthly swordfish (Xiphias gladius) catches in the Greek Seas during 1982-1996 and 1997 respectively, using catches reported by the National Statistical Service of Greece (NSSG). Forecasts built with X-11 were also compared with those derived from ARIMA andWinter’s exponential smoothing (WES) models. The X-11 method captured the features of the study series and outperformed the other two methods, in terms of both fitting and forecasting performance, for all the accuracy measures used. Thus, with the exception of October, November and December 1997, when the corresponding absolute percentage error(APE) values were very high (as high as 178.6%) because of the low level of the catches, monthly catches during the remaining months of 1997 were predicted accurately, with a mean APE of 12.5%. In contrast, the mean APE values of the other two methods for the same months were higher (ARIMA: 14.6%; WES: 16.6%). The overall good performance of X-11 andthe fact that it provides an insight into the various components (i.e. the seasonal, trend-cycle and irregular components) of the time series of interest justify its use in fisheries research. The basic features of the swordfish catches revealed by the application of the X-11 method, the effect of the length of the forecasting horizon on forecasting accuracy and the accuracy of the catches reported by NSSG are also discussed.