Autohtoni nasadi mekušaca: strategijsko upravljanje, zaštita, obnavljanje i eksploatacija

It is no secret that commercially important oyster beds are declining or fluctuating sharply all over the world. In Chesapeake Bay (USA) from 1985-1990 there was a sharp decline in production from 700,000 - 800,000 kg to 4,000 - 5,000 kg. In Australia production has declined since World War II to 45% of earlier levels. The same has occurred in the Mediterranean: according to F.A.O. (1997) European oyster stocks increased from 1950-1990, but by 1995-2000 they had declined almost linearly to about one-half earlier amounts. In addition, other Molluscs are considered to represent “concave downward” declining stocks (F.A.O., 1997). The main producing countries in the East Mediterranean for the European flat oyster are Italy (46.1%), Greece (4.4%), Turkey (2.2%), and Croatia (1.5%). For other species, the main producing countries are Italy (69.0%), Greece (16.0%), Turkey (2.2%), and Croatia (3.7%). The Adriatic, with considerable river input and a high degree of eutrophication, is important for mollusc production. The main question, however, is how stable and sensitive this industry is. Starting from the main issue that the natural stocks decline the need for the elaboration of a strategic management plan for the native mollusc beds is imperative. Strategic planning is an important tool for any sector when we need to do more than react to events as they unfold. Strategic planning involves a realistic assessment of the external environment and the factors bearing on it, now and in the future. Arising from this analysis, various “strategies” can be determined which will enable overall objectives to be met. The framework of a strategic management plan includes discussion and measures on issues such as property rights, policy issues affecting water quality and quality assurance, other aspects of government administration, generic promotion and R&D. Issues affecting business structure, the specific production technology employed, brand development and related aspects of marketing, are more likely to reflect the goals of individual businesses, although there may be a role for voluntary collective action (but not mandatory, or industry-wide action) in some circumstances. Strategic planning for the development of mollusc industry is not strictly a scientific or a administration problem to solve. It is a multi-parametric and multi-sectoral problem and as in any similar case, our inability to handle multi-parametric problems results to plans with limited results or more frequently, to disasters.Općenito je poznato da su nasadi kamenica posvuda u svijetu izloženi većim oscilacijama ili su u opadanju. U SAD-u, Chesapeake Bay, u razdoblju od 1985. do 1990. zabilježeno je znatno opadanje u proizvodnji sa 700 - 800.000 kg godišnje na 4.000 - 5.000 kg godišnje. U Australiji proizvodnja je u padu od Drugog svjetskog rata, i iznosi 45%. Slično je i na Mediteranu: prema godišnjaku FAO (1997.) europski stokovi kamenica pokazivali su rast u razdoblju 1950.-1990., nakon toga opadanje je linearnog oblika pa od 1995. do 2000. iznosi 45-50%. Što se tiče proizvodnje ostalih pripadnika skupine školjkaša, smatra se da su stokovi u opadanju te prate “konkavno silazeću” putanju (FAO, 1997.). Glavni proizvođači europske plosnate kamenice na istočnom Mediteranu su: Italija (46,1%), Grčka (4,4%), Turska (2,2%) i Hrvatska (1,5%). Glavne zemlje proizvođači skupine mekušaca su: Italija (69,0%), Grčka (16,0%), Turska (2,2%) i Hrvatska (3,7%). Površina Jadranskog mora, sa značajnim dotokom slatke vode i visokim stupnjem eutrofikacije, bitno je područje za proizvodnju mekušaca. Ključno je pitanje pritom koliko je ova industrija osjetljiva i stabilna

Autohtoni nasadi mekušaca: strategijsko upravljanje, zaštita, obnavljanje i eksploatacija

It is no secret that commercially important oyster beds are declining or fluctuating sharply all over the world. In Chesapeake Bay (USA) from 1985-1990 there was a sharp decline in production from 700,000 - 800,000 kg to 4,000 - 5,000 kg. In Australia production has declined since World War II to 45% of earlier levels. The same has occurred in the Mediterranean: according to F.A.O. (1997) European oyster stocks increased from 1950-1990, but by 1995-2000 they had declined almost linearly to about one-half earlier amounts. In addition, other Molluscs are considered to represent “concave downward” declining stocks (F.A.O., 1997). The main producing countries in the East Mediterranean for the European flat oyster are Italy (46.1%), Greece (4.4%), Turkey (2.2%), and Croatia (1.5%). For other species, the main producing countries are Italy (69.0%), Greece (16.0%), Turkey (2.2%), and Croatia (3.7%). The Adriatic, with considerable river input and a high degree of eutrophication, is important for mollusc production. The main question, however, is how stable and sensitive this industry is. Starting from the main issue that the natural stocks decline the need for the elaboration of a strategic management plan for the native mollusc beds is imperative. Strategic planning is an important tool for any sector when we need to do more than react to events as they unfold. Strategic planning involves a realistic assessment of the external environment and the factors bearing on it, now and in the future. Arising from this analysis, various “strategies” can be determined which will enable overall objectives to be met. The framework of a strategic management plan includes discussion and measures on issues such as property rights, policy issues affecting water quality and quality assurance, other aspects of government administration, generic promotion and R&D. Issues affecting business structure, the specific production technology employed, brand development and related aspects of marketing, are more likely to reflect the goals of individual businesses, although there may be a role for voluntary collective action (but not mandatory, or industry-wide action) in some circumstances. Strategic planning for the development of mollusc industry is not strictly a scientific or a administration problem to solve. It is a multi-parametric and multi-sectoral problem and as in any similar case, our inability to handle multi-parametric problems results to plans with limited results or more frequently, to disasters.Općenito je poznato da su nasadi kamenica posvuda u svijetu izloženi većim oscilacijama ili su u opadanju. U SAD-u, Chesapeake Bay, u razdoblju od 1985. do 1990. zabilježeno je znatno opadanje u proizvodnji sa 700 - 800.000 kg godišnje na 4.000 - 5.000 kg godišnje. U Australiji proizvodnja je u padu od Drugog svjetskog rata, i iznosi 45%. Slično je i na Mediteranu: prema godišnjaku FAO (1997.) europski stokovi kamenica pokazivali su rast u razdoblju 1950.-1990., nakon toga opadanje je linearnog oblika pa od 1995. do 2000. iznosi 45-50%. Što se tiče proizvodnje ostalih pripadnika skupine školjkaša, smatra se da su stokovi u opadanju te prate “konkavno silazeću” putanju (FAO, 1997.). Glavni proizvođači europske plosnate kamenice na istočnom Mediteranu su: Italija (46,1%), Grčka (4,4%), Turska (2,2%) i Hrvatska (1,5%). Glavne zemlje proizvođači skupine mekušaca su: Italija (69,0%), Grčka (16,0%), Turska (2,2%) i Hrvatska (3,7%). Površina Jadranskog mora, sa značajnim dotokom slatke vode i visokim stupnjem eutrofikacije, bitno je područje za proizvodnju mekušaca. Ključno je pitanje pritom koliko je ova industrija osjetljiva i stabilna

Razmnožavanje kozice Penaeus (Melicertus) kerathurus u zaljevu Amvrakikos, zapadna Grčka

The reproduction of the karamote prawn, Penaeus (Melicertus) kerathurus (Forskål 1775), was studied for the native population in Amvrakikos Gulf (Ionian Sea; western Greece). Sampling was carried out on a monthly basis between June 1999 and May 2001. The results showed that the shrimp Penaeus (Melicertus) kerathurus reproduction period spans between late April and late September. The size-at-maturity was estimated at a size of 45.23 mm carapace length (or 156.2 mm in total length). The smallest mature female in the samples was found to have 30 mm CL or 113.95 mm TL. Maximum gonadosomatic index (GSI) was estimated to be 9.62% for female shrimps at stage IV gonad maturity stage. The population gonadosomatic index peaks in May with an average value of 6.895%. Potential fecundity was estimated to be 154600 of oocytes per g of gonad tissue at the stage IV (mature female). Monthly sex ratios (males/females) were found greater than 1 throughout the year with maximum values reaching 2.5. A new life cycle pattern is proposed for this particular population.Razmnožavanje kozice, Penaeus (Melicertus) kerathurus (Forskål, 1775), je istraživano na populacijama iz prirodne sredine na području zaljeva Amvrakikos (Jonsko more, zapadna Grčka). Uzorkovanje je obavljeno svakog mjeseca u razdoblju između lipnja 1999. godine i svibnja 2001. godine. Rezultati istraživanja pokazuju da se kozica mrijesti u razdoblju travanj-rujan. Veličina pri kojoj kozica dosiže spolnu zrelost iznosi 45.23 mm dužina karapaksa (156.2 mm ukupna dužina). Utvrđena je najmanja spolno zrela ženka u uzorku pri dužini 30 mm dužina karapaksa (113.95 mm ukupna dužina). Najveća izračunata vrijednost gonadosomatskog indeksa iznosi 9.62% za ženke pri stadiju IV zrelosti gonada. Gonadosomatski indeks za čitavu populaciju ima svoj maksimum u svibnju pri srednjoj vrijednosti od 6.895%. Izračunati potencijalni fekunditet iznosi 154600 oocita po gramu tkiva gonada pri stadiju IV (zrela ženka). Mjesečni omjer spolova (mužjak/ženka) ima vrijednosti veće od 1 tijekom cijele godine uz maksimalnu vrijednost 2.5. Iznesen je i predložak obrasca novog životnog ciklusa populacije na istraživanom području

Distribution and population structure of the red shrimp (

The distribution and population structure of the red shrimp, Aristeus antennatus, were investigated for an unexploited fishing ground in the Greek Ionian Sea (middle-eastern Mediterranean). A total of 8618 specimens, 7273 females and 1345 males was caught during a 12-month survey, from January to December 1997, at depths ranging from 400 to 800 m. Monthly size frequency distributions were analysed using different techniques, resulting in estimates of growth and mortality. Carapace lengths (cephalothoracic lengths, CL) ranged between 12 and 62 mm for females and 9 and 45 mm for males. The mean size of specimens exhibited statistically significant differences in relation to sex and months. Recruitment of both sexes occurred in mid-winter (January). Only the mean size of females seemed to increase with depth. Estimation of the von Bertalanffy growth parameters revealed high k values and a life expectancy of 4 and 5 years for males and females, respectively. A high percentage of specimens bore spermatophores during May and August, indicating that these months were peak breeding periods. Natural mortality rates ranged from 0.55 to 0.70 for females and from 0.62 to 0.79 for males, depending on the method used. Based on its biology and population dynamics, it appears that the red shrimp population in the study area has the potential to support a viable fishery

Estructura y diversidad de las asociaciones de peces demersales: el papel de la pesquería

Seasonal experimental trawl surveys were carried out in the Northern Aegean and Thracian seas (NE Mediterranean, Greece), from summer 1990 to autumn 1993, during which a total of 172 fish species were caught. In these areas, fishing pressure is very high, since approximately 50% of the Greek otter trawl fleet operates there, producing more than 57% of the total demersal landings. Different statistics were used to assess spatial structure, seasonal changes and diversity of the demersal fish assemblages on the continental shelf and upper slope. The following measures were applied to the species abundance matrix: species diversity, species richness, evenness and dominance. The analysis of 501 bottom trawls revealed that, in general, species diversity, richness and evenness decreased with water depth, with the highest values at depths 200 m. The effect of depth on the diversity patterns observed was always significant, while seasonal trends were similar with those described for the overall diversity characteristics in each area. Classification and ordination methods showed the existence of 4 groups associated with the continental shelf and upper slope in each area. Classification of the top ranking species at each group and area revealed that commercially important species were dominant in the shallowest zone (Se realizaron pescas de arrastre experimentales en los mares Egeo septentrional y de Tracia (NE Mediterráneo, Grecia) desde el verano de 1990 al otoño de 1993, durante las cuales se capturó un total de 172 especies de peces. En estas áreas, la presión pesquera es muy elevada, puesto que aproximadamente el 50% de la flota griega de arrastre con puertas faena allí, produciendo más del 57% del total de desembarcos de especies demersales. Se utilizaron diferentes estadísticos para evaluar la estructura espacial, los cambios estacionales y la diversidad de las asociaciones de peces demersales en la plataforma continental y parte superior del talud. Se estimaron los siguientes parámetros a partir de la matriz de abundancia específica: diversidad específica, riqueza específica, uniformidad y dominancia. El análisis de 501 pescas de arrastre reveló que, en general, la diversidad específica, la uniformidad y la dominancia decrecían con la profundidad del agua, con valores máximos a profundidades 200 m. El efecto de la profundidad en las pautas de diversidad observadas fue siempre significativo, mientras que las tendencias estacionales fueron similares a las descritas para todas las características de la diversidad en cada área. Los métodos de clasificación y ordenación mostraron la existencia de 4 grupos asociados con la plataforma continental y parte superior del talud de cada área. La clasificación de las primeras especies por abundancia en cada grupo y área reveló que las especies importantes desde el punto de vista comercial eran dominantes en la zona más somera

Juvenile cephalopods collected in the midwater macroplankton over a trench in the Aegean Sea (Northeastern Mediterranean)

A total of 45 cephalopods, comprising 8 identified species and 1 unidentified early juvenile, were collected during a single cruise in the mesobathyal basins of the North Aegean Sea. Horizontal hauls were carried out at depths of 250, 500, 750, and 1000 m. Cephalopods were most frequent at 250 m. The following cephalopod taxa were identified: Heteroteuthis dispar, Histioteuthis reversa, Histioteuthis bonnellii, Pyroteuthis margaritifera, Chiroteuthis veranyi, Ancistrocheirus lesueuri. Octopus salutii, Octopus vulgaris, and one unidentified early juvenile onychoteuthid. Heteroteuthis dispar was the most common species. Chiroteuthis veranyi and Ancistrocheirus lesueuri are new records for the Aegean Sea and the latter also for the Eastern Mediterranean

Notes on Brachioteuthis riisei (Steenstrup, 1882) and Onychoteuthis banksi (Leach, 1817)(Cephalopoda: Teuthoidea) found in the Aegean Sea

The occurrence of Brachioteuthis riisei and Onychoteuthis banksi in the region of Argosaronikos (Aegean Sea) is reported in this note. Both species were collected by the experimental bottom trawl net used in the framework of the International Bottom Trawl Survey in the Mediterranean (MEDITS). A single individual of Brachioteuthis riisei was caught in June 1997, between 380-418 m of depth. It was a fully mature female with a mantle length of 66 mm, representing the largest individual ever caught in the Mediterranean and the first one recorded in the Aegean Sea. Five specimens of Onychoteuthis banksi were found in June 1997 and June 1998 at depths ranging between 685 and 760 m. All specimens were immature their size ranging from 55 to 107 mm DML. This is the first finding of the species in the Aegean Sea and the Eastern Mediterranean (east of 23¡ E)