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

Growth and Gonad Changes in Stony Sea Urchin, Paracentrotus Lividus (Lamark, 1816) Fed Artificially Formulated Feed and Benthic Macrophyte Diet

This study reported the efficiency of artificially formulated feed and benthic macrophyte diet on growth and gonad development of cultured stony sea urchin, Paracentrotus lividus (Lamark, 1816). An initial sample of 720 individual urchins was gathered in coastal area of SE Adriatic, near Dubrovnik, Croatia and for the purposes of the experiment, was held in a flow-through system. Sea urchin were fed four test diets A, B, C and D. Diet A consisted of seaweeds collected in the natural habitat of sampled sea urchin, artificial diets B, C, and D contained a different ratio of ingredients. The feed mixtures differed in respect to corn meal content; B (22%), C (30%) and D (35%) as well as the distribution of fish meal content; B (15%), C (5%) and D (0%). Prior to the commencement of feeding, sea urchins in all groups were starved for 15 days. During the period of starvation, recorded total urchin weight, gonadosomatic index (GSI) and gonad weight values for all experimental groups, showed a declining trend except in the control group, where they stayed the same. After 30 days, the declining trend of morphometric values was recorded for treatment A and the control group. During the two months of the intensive feeding conditions in the regimes with artificially prepared feed, B, C and D a growing trend was recorded for all morphometric values, and it was particularly evident in the treatment C. In the last month of the experiment, a significant decline in the GSI and gonad weight values were observed for the groups, A and the control. The differences among the artificially formulated feeds expressed through increase of GSI and gonad mass values revealed that the best among them was artificial feed C whose variance in consistence of essential nutritional components fits between prepared feeds B and D. Based on the results of our study we conclude that the artificially formulated feed is adequate food for sea urchins in a controlled environment, especially when it contains a smaller animal protein component (5- 10%) and a larger share of plant components (over 90%)

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

A Comparison of Traditional and Locally Novel Fishing Gear for the Exploitation of the Invasive Atlantic Blue Crab in the Eastern Adriatic Sea

The Atlantic Blue Crab Callinectes sapidus has been recognized as invasive in the Mediterranean Sea, where it now provides a significant contribution to artisanal fisheries. In this study, we compared the efficiency, selectivity, and productivity of American wire crab traps and traditional fyke nets for the capture of Blue Crabs in a study conducted from June to December 2019 in the Parila Lagoon (River Neretva Estuary, Croatia). A total of 7707 specimens were caught in 15 wire traps, comprising 6959 males and 749 females. The total catch using 50 traditional fyke traps was 1451 crabs, of which 1211 were males and 240 were females. In general, wire crab traps showed a higher capture selectivity and economic performance compared to fyke nets. The catch per unit effort (CPUE) was 102.76 kg for the American wire crab trap and 5.96 kg for the traditional fyke net. The CPUE of gravid female Blue Crabs was lower for the wire traps than the fyke nets. Herein, the utility of crab traps as selective fishing gear for the capture of Blue Crabs, and management tools for control of the reproductive and recruitment phases of the crab, are discussed, with the perspective of future exploitation of the species as a commercially valuable shellfish product in the Mediterranea

Dozrijevanje i novačenje olige, Atherina boyeri Risso 1810(Pisces: Atherinidae) na ušću Male Neretve (jugoistočni Jadran, Hrvatska)

Characteristics of maturation and recruitment of the sand smelt, Atherina boyeri, from the Mala Neretva River estuary in the southeastern Adriatic, Croatia in 2001/2, are presented. The average gonadosomatic index (GSI) during a 12-month period was 1.59% for females and 2.1% for males. The highest value was in April, 5.4% for females and 4.7% for males. The smallest mature female was 5.2 cm total length. Fifty percent of the females were mature at 7.75 cm total length. New juveniles began to recruit in June and July and later appeared in fewer numbers. In general, the GSI was lower than in other sand smelt populations. The reasons are difficult to determine but might be partly explained by the high and unpredictable temperature and salinity variations in the researched area that have led to previously described disturbances of the sand smelt life cycle, as in feeding and a high incidence of spinal deformities.Prikazane su karakteristike dozrijevanja i novačenja olige, Atherina boyeri na ušću Male Neretve, na srednjem dijelu istočne obale Jadrana, Hrvatska u 2001 i 2002. Prosječni gonadosomatski indeks tijekom 12-mjesečnog razdoblja za ženke je iznosio 1,59%, a za mužjake 2,1%. Najveća vrijednost je bila u travnju, za ženke 5,4%, a za mužjake 4,7%. Najmanja zrela ženka je zabilježena pri ukupnoj dužini 5,2 cm, a 50% ženki je bilo zrelo pri ukupnoj dužini 7,75 cm. Nova mlađ se počinje novačiti u lipnju i srpnju, a pojavljuje se i kasnije, ali u manjem broju. Vrijednosti GSI su uglavnom manje nego kod ostalih istraživanih populacija olige. Teško je zaključiti koji je razlog, ali djelomično se može objasniti velikim i nepredvidljivim kolebanjima temperature i slanosti, kod kojih su već opisani različiti poremećaji životnog ciklusa olige na istraživanom području, u ishrani i visokoj učestalosti deformacija kralješnice

Reproduktivna strategija kokotića, Lepidotrigla dieuzeidei Blanc and Hureau, 1973 iz jugoistočnog dijela Jadranskog mora

This study provides the first data on the reproductive biology of the spiny gurnard Lepidotrigla dieuzeidei. A total of 1027 individuals were collected monthly from September 2011 to August 2012. The total length of the individuals in the sample ranged from 7.46 cm to 14.62 cm with a female to male ratio of 1 to 0.59. Positive allometric growth was observed for both females (b=3.07) and males (b=3.08). Variations of condition factor were similar in both sexes with mean values of 1.07 for females and 1.01 for males. The fish L. dieuzeidei had a long spawning period extending from November to July based on monthly values of gonadosomatic index. Histological analysis showed that this fish was multiple synchronous developments of ovaries with multiple spawning events. The ovaries were always represented with a group of primary oocytes and a diverse population of vitel-logenic oocytes, each specially recruited during the final stages of maturation in uniform or uneven phases. Batch fecundity was estimated gravimetrically using the hydrated oocyte method and was estimated to be around 558 to 10.230 oocytes per female. L. dieuzeidei is an important by-catch species and data from this study represent a valuable contribution to stock management.Ovo istraživanje donosi prve podatke o reproduktivnoj biologiji kokotića, Lepidotrigla dieuzei-dei. Ukupno je prikupljeno 1027 jedinki, uzorkovano je mjesečno od rujna 2011. do kolovoza 2012. Ukupna duljina jedinki bila je u rasponu od 7,46 cm do 14,62 cm s omjerom spolova ženke:mužjaci 1:0,59. Pozitivan alometrijski rast zabilježen je i kod ženka (b = 3,07) i kod mužjaka (b = 3,08). Promjene indeksa kondicije bile su slične kod oba spola sa srednjim vrijednostima od 1,07 za ženke i 1,01 za mužjake. Temeljem mjesečnih vrijednosti gonadosomatskog indeksa utvrđeno je da kokotić ima dugo razdoblje mriješćenja, od studenog do srpnja. Histološka analiza pokazala je multipli sinkroni razvoj jajnika s više razdoblja mriješćenja. U jajnicima su uvijek bile zastupljene skupine primarnih oocita i raznovrsni stadiji vitelogenih oocita, koji su regrutirani u posljednjim stadijima sazrijevanja u jednoličnim ili neravnomjernim fazama. Fekunditet je procijenjen gravimetrijski primjenom metode hidratiziranih oocita i iznosi oko 558 do 10230 oocita po ženki. Kokotić je važna vrsta u prilovu i podatci iz ovog istraživanja predstavljaju značajan doprinos upravljanja stockom

THE BASIS OF COASTAL FISHERY MANAGEMENT FOR SMALL FISHING COMMUNITIES: THE CASE OF THE SHRIMP (PENAEUS KERA THURUS) FISHERY IN WESTERN GREECE

The fishery for Penaeus kerthurus in western Greece illustrates key features of the balance that must be struck to manage marine resources in small coastal communities, whether in Greece or in Croatia

Novačenje i sastav hrane mlađi cipla balavca Liza ramada (Risso, 1826) na ušću rijeke Neretve (istočni Jadran, Hrvatska)

The present paper describes the recruitment and food composition of thin-lipped grey mullet, Liza ramada (Risso, 1826) juveniles in the estuary of the Neretva River in the southeastern Adriatic. Thin-lipped mullet appeared in the Port of Ploče in February. The relationships between total length, standard length, and weight showed a remarkably good fit to the expected allometric model, with b=3 for total length. Twelve different animal food categories were identified. The greatest diversity was recorded in April at the Port of Ploče when 10 categories were present. In addition, six diatom taxa were noted. Harpacticoid copepods were the most common prey (39%) in these samples, followed by insects (32%) and cladocerans (12%). All other prey accounted for less than 4%. Insects represented 99% of prey in the stomachs of specimens sampled from the freshwater Crna Rijeka River. Thin-lipped mullet juveniles were not found on sandy beaches or natural bays around the port. It thus appears that juveniles find the port area to be a habitat with the favorable characteristics of a brackish water nursery: of predators, lower salinity, and high food availability. These all promote better survival and recruitment in this area of the Croatian Adriatic.U ovom radu opisuju se novačenje i sastav hrane mlađi cipla balavca Liza ramada na ušću rijeke Neretve u jugoistočnom Jadranu. Cipal balavac se pojavljuje u luci Ploče tijekom veljače. Odnosi između ukupne dužine, standardne dužine i mase pokazuju izuzetno dobro poklapanje s očekivanim alometrijskim modelom, za vrijednost alometrijskog koeficijenta b=3 za ukupnu dužinu. Određeno je dvanaest različitih kategorija hrane. Najveća raznolikost, 10 skupina plijena, je utvrđena u travnju u luci Ploče. Dodatno je utvrđeno 6 taksonomskih kategorija alga kremenjašica. Harpaktikoidni veslonošci su najčešći plijen (39%) mlađi cipla balavca, zatim slijede kukci (32%) i rašljoticalci (12%). Na sav ostali plijen otpada manje od 4%. Kukci predstavljaju 99% plijena utvrđenog u probavilima jedinki prikupljenih iz Crne rijeke. Mlađ cipla balavca nije utvrđena na pješčanim plažama i zaljevima šireg područja ušća Neretve. Smatra se da je brojnost mlađi cipla balavca u luci Ploče u svezi s povoljnim uvjetima staništa kao što su: manji broj predatora, niža slanost i veća količina dostupne hrane. Sve navedeno pogoduje uspješnijem novačenju cipla balavca u ovom dijelu hrvatskog Jadrana

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

Population Dynamics and Reproduction of Mediterranean Green Crab Carcinus aestuarii in Parila Lagoon (Neretva Estuary, Adriatic Sea, Croatia) as Fishery Management Tools

AbstractPopulation structure, age, growth, mortality, and reproduction patterns of the Mediterranean green crab Carcinus aestuarii were determined for the native population in Parila Lagoon (Neretva Estuary, Middle Adriatic, Croatia). The population size structure showed two distinct cohorts: (1) specimens with a carapace width of 20–34 mm and dominated by females and (2) large-sized specimens with a carapace width > 34 mm with males significantly dominating and no females found above 46 mm. Males appeared to grow faster than females in the first and second year of the life cycle. Most of the natural mortality (70.4%) occurred during the first year of life. This indicates high predation pressure from fish and other crab species on small-sized (less than 25 mm) C. aestuarii cohorts. The peak of ovigerous female occurrence occurred in January 2015. A very small percentage of ovigerous females appeared in June 2015. The 50% ovigerous size for the population was estimated at a carapace width of 29.65 mm and w..