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.

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

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

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

Odnos dužine i maksimalnog obujma za 24 riblje vrste u sjevernom Egejskom moru (istočno Sredozemno more)

The knowledge of morphological relationships and particularly of those concerning fish body girth (G) with total length (TL) is necessary in gear selectivity and specifically the technical measures to avoid capture of undersized individuals. This study concerns 24 marine species exploited by the small-scale coastal fleet in the Aegean Sea (eastern Mediterranean Sea), for 6 of which, the TL-G relationships are mentioned for the first time in the Mediterranean Sea and the adjacent seas. Samples were collected seasonally, from April 2016 to February 2017. The coefficients of the linear regression of body girth in three body positions, (Geye, posterior to the eye; Ghead at the posterior end of the operculum; Gmax at the maximum body depth), with the total length were estimated for each species and for the groups formatted when Geye, Ghead and Gmax were plotted against total length for all the species combined. Statistically significant differences among the three groups were detected (ANCOVA, P<0.001). Comparison of the total length-body girth relationships for 18 species previously studied in different geographic areas of the Mediterranean and the adjacent seas, showed differences mainly with the results from Portuguese waters for certain species populations. Based on the resulted equations, the maximum girth (G max) corresponding to the Minimum Conservation Reference Size (MCRS) and to the total length at maturity (L m) were calculated for each species. Identified mesh sizes respective to G max values were quite larger than the minimum legal mesh size for gillnets and the inner sheet of trammel nets, indicating that the relevant current fisheries regulations cannot meet the requirements for sustainable exploitation of fish resources.Poznavanje morfoloških odnosa, a posebno onih koji se tiču maksimalnog obujma tijela ribe (G) s ukupnom dužinom (TL) potrebito je za određivanje selektivnosti alata, a posebno za tehničke mjere za izbjegavanje hvatanja nedoraslih jedinki. Ova studija se odnosi na 24 morske vrste koje se iskorištavaju u priobalnoj ribolovnoj floti u Egejskom moru (istočno Sredozemno more), za 6 od kojih se TL-G odnosi prvi put spominju u Sredozemnom moru i susjednim morima. Uzorci su prikupljani sezonski, od travnja 2016. do veljače 2017. Koeficijenti linearne regresije obujma tijela u tri položaja tijela (G eye, posteriorno od oka; G head na stražnjem kraju operkuluma; Gmax na maksimalnoj visini tijela), s ukupnom duljinom procijenjene su za svaku vrstu i za skupine oblikovane kada su Geye, Ghead i Gmax ucrtani u odnosu na ukupnu duljinu za sve vrste zajedno. Utvrđene su statistički značajne razlike između tri skupine (ANCOVA, P<0,001). Usporedba odnosa ukupne duljine i obujma tijela za 18 vrsta koje su prethodno istraživane u različitim geografskim područjima Sredozemlja i susjednih mora, pokazala je razlike uglavnom s rezultatima iz portugalskih voda za određene populacije vrsta. Na temelju dobivenih jednadžbi izračunat je maksimalni obujam (Gmax) koji odgovara minimalnoj referentnoj veličini očuvanja (MCRS) i ukupnoj dužini pri zrelosti (Lm) za svaku vrstu. Identificirane veličine oka koje odgovaraju Gmax vrijednostima bile su dosta veće od minimalne zakonske veličine oka za mreže stajačice i unutarnju ploču troslojnih mreža, što ukazuje da relevantni trenutačni propisi o ribarstvu ne mogu ispuniti zahtjeve za održivo iskorištavanje ribljih resursa

Progress towards ending overfishing in the Northeast Atlantic

The reformed Common Fisheries Policy of the EU, in force since 2014, stipulates that overfishing by the fleets of its member states has to end latest in the year 2020. This study examines exploitation and status of 119 stocks fished by 20 countries in the Northeast Atlantic. In the year 2018, about 40% of the stocks were still subject to overfishing (F > Fmsy), about 34% of the stocks were outside safe biological limits (B < Bpa) and about 68% of the stocks were too depleted to produce maximum sustainable yields (B < Bmsy). Reduction in the number of overfished stocks has stalled, possible because of an agreement between the European Commission (EC) and the International Council for the Exploration of the Seas (ICES), its advisory body for total allowed catches (TACs), wherein the EC requests ICES to give TAC advice leading to overfishing for many stocks. As a result, it is unlikely that overfishing will end in the Northeast Atlantic in 2020

Progress towards ending overfishing in the Northeast Atlantic

The reformed Common Fisheries Policy of the EU, in force since 2014, stipulates that overfishing by the fleets of its member states has to end latest in the year 2020. This study examines exploitation and status of 119 stocks fished by 20 countries in the Northeast Atlantic. In the year 2018, about 40% of the stocks were still subject to overfishing (F > Fmsy), about 34% of the stocks were outside safe biological limits (B < Bpa) and about 68% of the stocks were too depleted to produce maximum sustainable yields (B < Bmsy). Reduction in the number of overfished stocks has stalled, possible because of an agreement between the European Commission (EC) and the International Council for the Exploration of the Seas (ICES), its advisory body for total allowed catches (TACs), wherein the EC requests ICES to give TAC advice leading to overfishing for many stocks. As a result, it is unlikely that overfishing will end in the Northeast Atlantic in 2020

Estimation of selectivity parameters for target and bycatch fishes of the trammel net fisheries in the northern Aegean Sea (eastern Mediterranean Sea)

The size selectivity of trammel nets was investigated in the northern Aegean Sea using 10 different inner-panel mesh sizes ranging from 16 to 70 mm nominal mesh size (bar length). Selectivity estimates were made for the eight most abundant target and bycatch fish species, namely black scorpionfish, Scorpaena porcus Linnaeus, 1758; annular seabream, Diplodus annularis (Linnaeus, 1758); red mullet, Mullus barbatus Linnaeus, 1758; surmullet, Mullus surmuletus Linnaeus, 1758; round sardinella, Sardinella aurita Valenciennes, 1847; European hake, Merluccius merluccius (Linnaeus, 1758); greater weever, Trachinus draco Linnaeus, 1758; and blotched picarel, Spicara flexuosum Rafinesque, 1810, which accounted for 51.5% by number and 42.7% by weight of the fish caught with trammel nets in the sea trials. The SELECT method was used to estimate the selectivity parameters. Five different selectivity functions (i.e., normal scale, normal location, gamma, log-normal, and bi-normal) were applied with the bi-normal function providing the best fit as it had the lowest deviance value for all species and the lowest values for the dispersion parameter (D/df). The mesh size of 16 mm in most of the cases retained specimens below the size at first maturity (Lm). The mesh size of 19 mm seems more appropriate for red mullet, surmullet, and blotched picarel, the mesh size of 22 mm for annular seabream and round sardinella, while for European hake and black scorpionfish, the mesh size larger than 26 mm would be more appropriate

Risk assessment of Golani’s round herring (Etrumeus golanii) in the Greek seas (northeastern Mediterranean Sea)

Greek waters are the recipient of several alien species, mainly through natural dispersal following invasion and establishment of non-indigenous species (NIS) in neighboring areas, making their monitoring and mitigating their effects of paramount importance. The European Union legislation framework toward alien species invasions considers risk assessments as the top of the spear for a first assessment of NIS and their potential to become invasive or not. The Union List has already included top priority species, with very few marine species. Golani’s round herring (Etrumeus golanii) is a species of round herrings in the family Dussumieriidae, a Lessepsian migrant and belonging to a group of NIS in the Mediterranean basin that are less studied. Its distribution range is mainly limited in the southeastern Mediterranean Sea, while in the Greek seas, it has not yet been observed in the north Aegean and Ionian seas, probably due to temperature and oceanographical reasons. Its presence in the basin is recorded by commercial fisheries landings in several countries (especially purse-seiners), indicating a potentially positive effect on commercial fisheries. A risk assessment of E. golanii in Greek waters was carried out in this work, based on the Risk Assessment Scheme developed by the GB Non-Native Species Secretariat (GB Non-Native Risk Assessment—GBNNRA). An overall semi-quantitative summary of risk, in terms of likelihood of events and magnitude of impacts, was facilitated for several attributors, including confidence levels for each one. The assessment highlighted a very likely possibility of introduction in the Greek seas from neighboring countries, as well as successful establishments of populations with high confidence levels. A moderate magnitude of impact regarding its further spread was deemed, while a minor one was indicated in terms of native species pressure and a minimal one in terms of economic costs and public health. Overall, E. golanii was not characterized as an invasive alien species (IAS) and local communities could benefit from its presence (commercial fisheries); however, further studies focusing on its reproduction and spawning grounds should be implemented