Biología reproductiva de la alacha (Sardinella aurita) en el Mediterráneo NE

The reproductive biology of round sardinella, Sardinella aurita Valenciennes, 1847, was studied for the first time in the north-eastern Mediterranean Sea. Round sardinella has gained much attention lately because of its biomass increase, which might be the result of climatic changes occurring across the Mediterranean Sea. Monthly samples were collected on board commercial purse-seiners for two complete year cycles (September 2000 to August 2002). Round sardinella is a gonochoristic fish. The overall female to male ratio was not statistically different (P=0.34) from unity, although it varied monthly and with the length of the fish. The seasonal changes in the gonadosomatic index and the macroscopic characteristics of gonads showed that round sardinella in the northern Aegean spawns between May and July. Male round sardinella reach first sexual maturity at a smaller total length than females (155.0 and 168.3 mm respectively). Mean absolute fecundity (FA) increased exponentially with body length (FA=0.0949xL4.22) and weight (FA=511.19xW1.02), with an average of ~21,000 oocytes produced per spawning female. Relative fecundity (FR) ranged between 242 and 681 oocytes/g of body weight (average: 445 oocytes/g). The frequency distribution of oocytes showed that round sardinella produces a single batch of oocytes. In general, the reproductive characteristics of round sardinella in the north-eastern Mediterranean Sea differed when compared to stocks from other areas of its distribution.La biología reproductiva de la alacha, Sardinella aurita Valenciennes, 1847 fue estudiada por primera vez en el Mediterráneo NE. Esta especie ha sido recientemente motivo de atención debido a su incremento de biomasa, que podría ser debido a cambios climáticos en el Mediterráneo. Se obtuvieron muestras mensuales a bordo de barcos de pesca con artes de cerco durante dos ciclos anuales completos (Septiembre de 2000-Agosto de 2002). La alacha es una especie gonocorista. Globalmente, la proporción de sexos no fue estadísticamente (P=0.34) diferente de la unidad. Los cambios estacionales en el índice gonadosomático y en las características macroscópicas de las gónadas mostraron que la época de puesta de la alacha en el norte del mar Egeo tiene lugar entre Mayo y Julio. Los machos de la alacha alcanzaron la madurez sexual a una talla total inferior a la de las hembras (155.0 y 168.3 mm, respectivamente). La fecundidad media absoluta (FA) se incrementó exponencialmente con la talla (FA=0.0949×L4.22) y peso (FA=511.19×W1.02), con una media de ~21,000 oocitos producidos por hembra madura. La fecundidad relativa (FR) osciló entre 242 y 681 oocitos/g de peso corporal (promedio: 445 oocitos/g). La distribución de frecuencias de los oocitos mostró que la alacha produce una única cohorte de oocitos. En general, las carácterísticas reproductivas de la alacha del Mediterráneo NE son distintas de las observadas en poblaciones de otras áreas de su distribución.

Age at maturity of Mediterranean marine fishes

In this review we collected data on the age at maturity (tm) and maximum reported age (tmax) for 235 stocks of Mediterranean marine fishes, belonging to 82 species, 37 families, 12 orders and 2 classes (Actinopterygii and Elasmobranchii). Among Actinopterygii (mean tm ± SD = 2.20 ± 1.43 y, n = 215), tm ranged from 0.3 y, for the common goby Pomatoschistus microps, to 12 y, for dusky grouper Epinephelus marginatus, while among Elasmobranchii (mean tm ± SD = 5.94 ± 2.47 y, n = 20), tm ranged between 2.7 y, for brown ray Raja miraletus, and 12 y for picked dogfish Squalus acanthias. Overall, the tmax ranged between 1 y, for transparent goby Aphia minuta, and 70 y, for wreckfish Polyprion americanus. The mean tmax of Actinopterygii (tmax ± SD = 10.14 ± 9.42 y) was lower than that of Elasmobranchii (tmax ± SD = 14.05 ± 8.47 y). The tm exhibited a strong positive linear relation with tmax for both Actinopterygii (logtm = 0.58 ´ logtmax – 0.25, r2 = 0.51, P < 0.001) and Elasmobranchii (logtm = 0.67 ´ logtmax – 0.006, r2 = 0.51, P = 0.007). The mean tm/tmax did not differ significantly with sex within Actinopterygii (ANOVA: F = 0.27, P = 0.60, n = 90; females: mean ± SD = 0.276 ± 0.143; males: mean ± SD = 0.265 ± 0.138) and Elasmobranchii (ANOVA: F = 1.44, P = 0.25, n = 10; females: mean ± SD = 0.499 ± 0.166; males: mean ± SD = 0.418 ± 0.133). Finally, the dimensionless ratio tm/tmax was significantly lower (ANOVA: F = 31.04, P < 0.001) for Actinopterygii (mean ± SD = 0.270 ± 0.135, n = 180) than for Elasmobranchii, (mean ± SD = 0.458 ± 0.152, n = 20), when stocks with combined sexes were excluded from the analysis

Sastav sakupljenih ličinki riba i njihova prostorna grupiranost tijekom ljetnog razdoblja u sjevernom Egejskom moru

Fish larvae were collected in two surveys, carried out at the beginning of July 2002 and 2003 in Kavala Gulf (northern Aegean Sea) aimed at studying ichthyoplankton species assemblages and station groupings. The similarity dendrograms revealed the existence of four species assemblages associated with three station groups in 2002 and five species assemblages associated with four station groups in 2003. These groupings were confirmed by non-metric multidimensional scaling (NMDS) analysis. Analysis of similarity showed that the station groups were significantly different for 2002 (global R=0.748; P<0.001) and 2003 (global R=0.931; P<0.001). High dissimilarity between species assemblages as obtained from dendrograms and NMDS analyses was also recorded for 2002 (global R=0.834; P<0.001) and 2003 (global R=0.767; P<0.001). The assemblage structure was mainly determined by the most abundant and frequently occurring larvae, especially the European anchovy (Engraulis encrasicolus), and was largely influenced by the reproductive traits and spatial distribution of adult fish. Differences among station groupings were also determined by the spatial occurrence and abundance of each taxon.Riblje ličinke su prikupljene tijekom dvaju istraživanja koja su provedena početkom srpnja 2002. i 2003. godine u zaljevu Kavala (sjeverni dio Egejskog mora) s ciljem utvrđivanja strukture ribljih vrsta i postojanih populacija. Sličnost dendograma otkrila je postojanje četiri populacije povezane s tri skupine u 2002. godini i pet populacija povezanih s četiri stalne skupine u 2003. godini. Te skupine su potvrđene pomoću ne-metričke analize višedimenzionalnih skala (NMDS). Analiza je pokazala da su grupe stalnih populacija bile značajno različite za 2002. godinu (globalno R = 0,748; P <0,001) i 2003 (globalno R = 0,931; P <0,001). Visoki stupanj različitosti između grupacija dobivenih od dendograma i NMDS analize također je zabilježena za 2002. godinu (globalno, R = 0,834; P <0,001) i 2003 (globalno, R = 0,767; P <0,001). Skupna struktura uglavnom je bila određena prema najrasprostranjenijim i učestalim ličinkama, posebice brgljuna (Engraulis encrasicolus), te je uvelike bila pod utjecajem reprodukcijskih obilježja i prostornom raspodjelom odraslih riba. Razlike između utvrđenih grupacija također su određene s obzirom na prostorno pojavljivanje i brojnost svake svojte

What’s on the (publication fee) menu, who pays the bill and what should be the venue?

We address the cost of access to knowledge and its ethical implications in ‘true’, ‘pseudo’ and ‘hybrid’ OA journals

A quantitative evaluation of a qualitative risk assessment framework: Examining the assumptions and predictions of the Productivity Susceptibility Analysis (PSA)

Qualitative risk assessment frameworks, such as the Productivity Susceptibility Analysis (PSA), have been developed to rapidly evaluate the risks of fishing to marine populations and prioritize management and research among species. Despite being applied to over 1,000 fish populations, and an ongoing debate about the most appropriate method to convert biological and fishery characteristics into an overall measure of risk, the assumptions and predictive capacity of these approaches have not been evaluated. Several interpretations of the PSA were mapped to a conventional age-structured fisheries dynamics model to evaluate the performance of the approach under a range of assumptions regarding exploitation rates and measures of biological risk. The results demonstrate that the underlying assumptions of these qualitative risk-based approaches are inappropriate, and the expected performance is poor for a wide range of conditions. The information required to score a fishery using a PSA-type approach is comparable to that required to populate an operating model and evaluating the population dynamics within a simulation framework. In addition to providing a more credible characterization of complex system dynamics, the operating model approach is transparent, reproducible and can evaluate alternative management strategies over a range of plausible hypotheses for the system

Trendovi iskorištavanja živih bogatstava Sredozemnog i Crnog mora

The exploitation trends of Mediterranean and Black Sea fisheries stocks were examined using the total annual catches, the variability of the mean trophic level of the catch and fishing-in-balance index for the period 1970-2010. Overall catches increased rapidly to their maximum levels by the late 1980s and then declined and remained rather stable at around 75% of their highest levels. The mean trophic level of the catches followed a similar pattern to the overall catches with constant (except for 2005-2007) but steady decline since the late 1980s. The annual catches of 2636 stocks were also analysed for the period 1970-2010 and classified into exploitation categories according to the catch-based method of stock classification. In 2010, about 22% of the stocks were depleted, 40% were overexploited, 24% were fully exploited while undeveloped/developing fisheries were confined to 14%. All analyses indicate that the Mediterranean and Black Sea fisheries are gradually contracting to unsustainable levels.Trendovi iskorištavanja živih bogatstava Sredozemnog i Crnog mora su analizirani pomoću ukupnih godišnjih ulova, varijabilnosti prosječne trofičke razine ulova te uravnoteženosti ribolovnog indeksa za razdoblje 1970.-2010. U kasnim 1980-im ukupni ulov se naglo povećao do svoje maksimalne moguće razine, a zatim je došlo do pada te je ostao prilično stabilan na razini od oko 75% od svoje najveće razine. Prosječne trofičke razine ulova slijede sličan obrazac ukupnih ulova s konstantnim (osim za razdoblje 2005.-2007.) i stalnim padom od kraja 1980-ih godina. Godišnji ulovi 2636 iskorištavanih stockova također su analizirani za razdoblje od 1970. do 2010. godine i podijeljeni prema eksploatacijskim kategorijama. U 2010. godini oko 22% zaliha živih bogatstava je bilo iscrpljeno, 40% se prekomjerno iskorištavalo, a 24% je doseglo maksimalnu razinu iskorištavanja. Sve analize upućuju na to da je iskorištavanje živih bogatstava Sredozemnog i Crnog mora doseglo maksimalne vrijednosti, pa čak u nekim slučajevima i do neodržive razine

Editorial note on reproductive biology of fishes

Fish reproductive biology (onset and duration of spawning, sex ratio, maturity stages, length and age at maturity, and fecundity) is important in fisheries research, stock assessment, and management. In this editorial note, we provide some criteria and recommendations on issues of fish reproductive biology, which may be useful in research planning, data analysis and presentation, as well as in manuscript preparation

Editorial note on weight–length relations of fishes

Weight-length relations of fishes are useful for estimation of biomass from length observations, e.g., in fisheries or conservation research. Here we provide some guidance to authors of such papers, in order to facilitate the publication and review process

Comunidades zooplanctónicas estivales en relación con parámetros ambientales en el golfo de Kavala, norte del mar Egeo

Shallow coastal areas are ecosystems with high productivity. Although the eastern part of the Mediterranean Sea is oligotrophic, the shallow coastal waters of the northern Aegean, such as Kavala Gulf, are productive due to the influence of the Black Sea water and the presence of freshwater input from three rivers. The aim of this work was to determine the structure of zooplankton communities in Kavala Gulf in the summer of 2002 and 2003 and to investigate their relation to environmental variables. Zooplankton communities were characterized by the presence of common coastal Cladocera, such as Penilia avirostris, small pelagic Copepoda, such as the calanoida Acartia clausi and the cyclopoida Oithona plumifera, and Tunicata, such as Oikopleura, Fritillaria and Doliolidae. The abundances corresponded to the peak of the warm period and were significantly greater in 2002 because of a P. avirostris bloom, which seemed to have better exploited the environmental sources favouring its dominance in the area. Overall, the structure of summer mesozooplankton communities in Kavala Gulf follows the pattern exhibited by mesozooplankton communities in other Greek coastal areas of the northern Aegean Sea.Las aguas costeras poco profundas son ecosistemas con alta productividad. Aunque el mar Mediterráneo oriental es oligotrófico, las aguas costeras poco profundas al norte del mar Egeo, como el golfo de Kavala, son productivas debido a la influencia de aguas provenientes del mar Negro y a los aportes de agua dulce procedentes de tres ríos. El objetivo de este trabajo fue determinar la estructura de las comunidades de zooplancton en el golfo de Kavala durante los veranos de 2002 y 2003, e investigar su relación con variables ambientales. Las comunidades de zooplancton se caracterizaron por la presencia de cladóceros costeros comunes, como Penilia avirostris, pequeños copépodos pelágicos, tales como el calanoide Acartia clausi y el ciclopoide Oithona plumifera, y tunicados como Oikopleura, Fritillaria y Doliolidae. Las abundancias correspondieron al pico del periodo cálido y fueron significativamente mayores en 2002 debido a una proliferación de P. avirostris, que parece que supo explotar mejor las condiciones ambientales favoreciendo su dominio en la zona. En general, la estructura de las comunidades de mesozooplancton de verano en el golfo de Kavala siguen el patrón exhibido por las comunidades de mesozooplancton en otras areas costeras griegas al norte del mar Egeo

A Bayesian population model to estimate changes in the stock size in data poor cases using Mediterranean bogue (Boops boops) and picarel (Spicara smaris) as an example

The paper presents an effort to build a biologically realistic, age structured Bayesian model for the stock assessment of data poor fisheries where only aggregated catch data is available. The model is built using prior information from other areas and ecologically or taxonomically similar species. The modeling approach is tested with data poor fisheries on the Cyclades islands in Greek archipelago. The two most important species in the area are selected: bogue (Boops boops) and picarel (Spicara smaris). Both are hermaphroditic. The only data available is the total catch from 1950 to 2010. Information was gathered about natural mortality, recruitment, growth, body size, fecundity, and sex ratio. There were significant problems in finding reliable prior information and a uniform prior was used for fishing mortality. The models at their present stage are not used to give management advice. The biological characteristics of the species in that area should be further studied. However, the posteriors of biological parameters reflect the best available knowledge on these species and they could be used in future studies or in simpler biomass dynamics models as priors