A review of length-weight relationships of fishes from Greek marine waters

This paper presents 649 length-weight relationships gathered from literature pertaining to 83 fish species, belonging to 34 families, throughout Greek marine waters. The value of the slope b ranged from 1.667 for Cepola macrophthalma to 3.707 for Mullus barbatus. The mean value of b was 2.989 (SD=0.339) and did not differ significantly from 3(t-test, p<0.05). The median value of b was 3.058 and 50% of the b values ranged between 2.900 and 3.186

Overlooked impacts and challenges of the new European discard ban

Discards are the portion of animal and plant material in the catch that is dumped back at sea. The Common Fisheries Policy plan proposed by the European Commission for 2014-2020 presents a controversial goal: to enforce the landing of fishing discards as a measure to encourage their reduction. This historical and political decision will shape the future of the fishing exploitation in European Seas. Discards generated by European fleets are not negligible, and its reduction is an ecological, socioeconomical and moral imperative. However, it must be achieved through the reduction in discards at source and the promotion of selective and non-destructive gears. We argue it is doubtful that this discard ban will result in an effective reduction of discards. The proposed measure may, in fact, negatively affect ecosystems at all levels of biological hierarchy by disregarding the Ecosystem-Based Approach to Fisheries and the Precautionary Principle. It could negatively impact several species by increasing fishing mortality, also commercial species if discards are not accounted in the total allowable catch. Communities preying on discards will likely be affected. The role discards currently play in the energy turnover of current ecosystems will be modified and should be fully evaluated. The landing of discards will likely generate new markets of fishmeal due to the growing demands for marine living resources. The ban will require substantial public investment to deal with technical problems on board and to control and enforce. Therefore, this measure should be only implemented after rigorous scientific and technical studies have been developed

Variability of physical factors relevant to fisheries production in the Mediterranean Sea, North Sea and Baltic Sea

Recent publications have shown that river runoff and wind mixing are two major environmental factors affecting productivity of fish populations in subtropical and tropical areas, as opposed to water temperature in colder waters. In the present paper, we compare the variability of seawater temperature, river runoff and wind mixing in three different seas: a subtropical sea (the Mediterranean) and two cold seas (the North Sea and the Baltic). Temperature variability decreased from colder to warmer areas. The highest temporal variability in the river runoff corresponded to rivers flowing into the Mediterranean, and the lowest corresponded to rivers flowing into the North Sea and the Baltic Sea. The variability in the wind mixing index (cube of the wind speed) depended on the area under consideration, and attained maximum values in the Cap Béar station (northwestern Mediterranean). The effect of these regional variability differences in environmental factors on fisheries production is briefly discussed.Investigaciones recientes demuestran que las descargas fluviales y los vientos son factores ambientales clave para la productividad de las poblaciones explotadas en zonas subtropicales y tropicales, mientras que en mares fríos la temperatura del agua constituye el factor ambiental más importante para la productividad pesquera. Este estudio compara las diferencias geográficas en la variabilidad temporal de tres factores físicos (temperatura del agua, aportes fluviales y velocidad del viento) en un mar subtropical (Mediterráneo) y dos mares fríos (Mar del Norte y Báltico). La variabilidad temporal de la temperatura del agua es mayor en los dos mares fríos que en el subtropical. Así mismo, los ríos que desembocan en el Mediterráneo presentan mayor variabilidad temporal en cuanto a los aportes fluviales que los ríos que desembocan en el Mar del Norte y el mar Báltico. La variabilidad temporal en el índice de mezcla del viento (velocidad del viento al cubo) es distinta según la zona que se considere, y es máxima en la estación de Cap Béar (Mediterráneo noroccidental). Finalmente, se discuten los efectos de esta variabilidad ambiental geográfica sobre las poblaciones explotadas.Instituto Español de Oceanografí

A century of trends in adult human height

Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5-22.7) and 16.5 cm (13.3-19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8-144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries

Global versus local changes in upwelling systems

Dans ce travail, nous analysons les principales caractéristiques des pêcheries marines grecques (composition des captures et densités) pour la période 1982-1989 ; les résultats sont discutés en termes de potentiel trophique des eaux maritimes grecques (abondance et productivité du phytoplancton et du zooplancton) et comparés à ceux obtenus dans d'autres zones (d'upwelling ou non). Des analyses multivariées (classification et hiérarchisation) sont faites sur les captures commerciales moyennes de 66 espèces (ou groupes d'espèces) de 16 zones de pêche appartenant à trois groupes : la zone S-SE de la mer Egée (et NW de la mer du Levantin), la mer Ionienne et la zone centrale de la mer Egée, et le N-NW de la mer Egée. La composition des captures diffère beaucoup d'une zone à l'autre. La capture moyenne de la zone S-SE de la mer Egée est dominée par les brochets et les bogues et, dans une moindre mesure, par les chinchards ; celle de la partie centrale de la mer Egée et de la mer Ionienne par les sardines, les chinchards, les bogues et les brochets ; et celle de la zone N-NW de la mer Egée par les anchois et les sardines. Les densités moyennes des captures de poissons pélagiques, démersaux et des captures totales diminuent entre 1982 et 1989 de 1,3, 0,83 et 2,13 t/km2 respectivement dans le N-NW de la mer Egée, à 0,25, 0,37 et 1,23 t/km2 dans le S-SE de la mer Egée, ces dernières valeurs se retrouvent aussi dans le mer Ionienne. De plus, un tel accroissement va de pair avec une décroissance de l'importance relative dans chacune des zones des espèces démersales. La densité des captures de poissons pélagiques dans la mer Ionienne et dans le S-SE de la mer Egée est de 3 à 150 fois plus faible que celle d'autres zones marines... (D'après résumé d'auteur

Intestine morphometrics of fishes: a compilation and analysis of bibliographic data

Background. The examination of morphological features related to feeding in fish, as well as their relation with body length, are of increasing scientific interest. In the present study, information on intestine (gut) morphometrics that appear in the relevant literature has been compiled, analysed, and discussed. Materials and methods. Search of gut-related bibliography was conducted, using online literature databaseson fish feeding and ecomorphology. The resulted data was tabulated. Relationships between mean, minimum, and maximum relative gut length (RGL) and intestine length weight index (ILW, Zihler’s index), as provided by the original author, with species’ fractional trophic levels (TROPHs; extracted from FishBase) were explored. Finally, using the relations between gut length (GL) and body length (L) provided by the original authors, regressions were reconstructed and compared based on species’ feeding habits and taxonomy. Results. The amount of information related to gut morphometrics referred to 498 species. The relations between GL and L referred to 71 species, but four species were omitted from the analyses. Mean, minimum, and maximum RLGand ILW values were negatively related (for all cases: P < 0.01) with TROPH. The GL–L regressions performed for 67 species revealed the presence of two major groups as herbivorous fishes and carnivorous fishes. Grouping according to species’ taxonomic order did not form any significant groupings. Conclusion. Existing information on intestine morphometrics is generally accumulated in a few scientific papers. All the analyses performed on the compiled data reinforced the pattern generally accepted that herbivores have longer intestines than carnivores. In addition, the influence of species’ evolutionary history on comparisons of gut length between species with different feeding habits was not verified. Finally, equations relating RGL and ILW to TROPH can be used for TROPH value estimates from morphological data that are easy to obtain, especially in the lack of species’ feeding habits data

Mouth allometry and feeding habits of some Mediterranean fishes

Background. Mouth characteristics are considered important yet restraining factors for food acquisition in fishes. Nevertheless, their relations with total length (TL) are not thoroughly examined. In the present study mouth characteristics were estimated for 61 fish species from the northern Aegean Sea and their relations with TL were established, and the relation of mouth area with feeding habits was tested. Materials and methods. TL, horizontal mouth opening (HMO), and vertical mouth opening (VMO) were measured in 61 species, and mouth area MA was estimated. Relations between mouth characteristics and TL were established using power regression, and the validity of the power model was tested, using Student’s t-test. In order to explore whether there is a grouping of species based on their feeding habits, the MA–TL regressions of all species were plotted together and the general regression lines per functional trophic group were compared using analysis of variance. Finally, the relative MA was estimated and related to trophic level. Results. All relations examined were statistically significant (P < 0.05), with only one exception (VMO–TL relation in Dentex dentex). The allometric model (for HMO–TL, MA–TL, and VMO–TL) was valid for the majority of species (52, 47, and 49 species, respectively), with positive allometry prevailing in the HMO–TL and MA–TL relations, and negative allometry in the VMO–TL relations. The analyses employed revealed that MA, for the same TL, increases faster in carnivores than in omnivores, and that in general carnivorous species tend to have larger mouths than omnivorous ones. Finally, there is a strong positive relation between relative MA and trophic level (P < 0.01). Conclusion. There is a strong relation of mouth characteristics to body length and feeding habits. These relations and the way that MA increases in relation to feeding habits could be attributed to structural changes in order for growing fish to meet their increased energetic demands. Establishing such relations is essential for estimating trophic levels of species, which are key parameters for ecosystem-based management models, when data on species’ feeding habits are not available