Modeliranje iseljavanja ličinki u malom zaštićenom morskom području: primjer slanih jezera na otoku Mljetu (Jadransko more)

This paper analyzes potential recruitment effect of endangered bivalve Pinna nobilis in a small marine protected area-Little Lake (Adriatic Sea). A box model has been applied for the estimation of residence time of the lake, forced by tides only at the open end of the lake system. The residence time of Little Lake was estimated to be 54 days. In our approach we assumed that P. nobilis larvae may be found in the surface waters only during the night, thus restricting their outgoing from the lake to about 7-8 hours per day in the June-August period, as the larvae need some time to reach surface waters. Therefore, the equivalent residence time of the larvae in Little Lake is estimated to be about 160-185 days. Knowing that the bivalve larva phase lasts between 3 and 5 weeks, one may estimate that only 11 to 22% of the larvae, respectively, leave Little Lake. From a conservation standpoint these low values imply a special level of protection within Mljet National Park. In addition, future climatic changes will affect the recruitment of P. nobilis, not only due to sea level rise but also with temperature and other changes which may influence its reproduction phase and larvae transport.U ovom se radu analizira mogućnost iseljavanja ličinki ugroženog školjkaša P. nobilis u malom zaštićenom morskom području–Malo Jezero (Mljet, Jadransko more). Pri izračunu vremena zadržavanja mora u jezeru primijenjen je model kutije, forsiran isključivo sa plimnim signalom na otvorenom kraju sustava jezera. Vrijeme zadržavanja mora u jezeru je procijenjeno na 54 dana. Pretpostavljeno je da se ličinke P. nobilis mogu naći u površinskom sloju samo za noćnih sati, što je ograničilo mogućnost iseljavanja iz jezera na 7-8 sati dnevno u razdoblju od lipnja do kolovoza, uz uvažavanje činjenica da je ličinki potrebno neko vrijeme da se uzdigne do površinskog sloja. Shodno tome, stvarno vrijeme zadržavanja ličinke je procijenjeno na 160 do 185 dana. Znajući da faza ličinki traje od 3 do 5 tjedana, procjena jest da samo 11 do 22% ličinki može napustiti Malo Jezero. Ovako niske vrijednosti impliciraju provođenje posebnih mjera zaštite Malog jezera u okviru Nacionalnog parka Mljet. Nadalje, predviđene klimatske promjene će utjecati na efekt iseljavanja P. nobilis, ne samo zbog promjene razine mora i režima izmjene vodenih masa u jezerima, već i zbog temperaturnih i drugih promjena koje mogu utjecati na reprodukcijsku fazu ličinke kao i na njezine sposobnosti gibanja

INTRODUCTIONS OF EXOTIC MARINE SPECIES ASSOCIATED WITH SHIPPING ACTIVITIES

An overview of some present day knowledge regarding introductions of exotic marine species associated with shipping activities is given in this paper. Transports of organisms via biofouling on ocean-going ships, water ballast and dispersal along rivers or canals are explained, illustrated by examples and their consequences and possible solutions are discussed. Special attention has been given to following species: Dreissena polymorpha, Mnemiopsis leidyi, Alexandrium sp. and Caulerpa taxifolia

Opis strukture zajednica školjkaša u hrvatskom dijelu Jadranskog mora - istraživanje hidrauličnom dredžom

Hydraulic dredge surveys of bivalve communities in the Croatian part of the Adriatic Sea were conducted from the Island of Rab in the north to the river Neretva estuary in the south during 2007 and 2008. The main objective of the study was to describe distribution and community structure of bivalves on soft sediments along the eastern Adriatic, primarily focusing on commercially important species in five main bivalve harvesting areas. A total of 105 hydraulic dredge samples were collected at depths ranging from 1 to 11 m. Sampled bivalves were separated in the field and frozen for later laboratory analysis that included species identification, abundance and biomass determination. Live specimens of 54 bivalve taxa were collected during this study, while 87 taxa were represented by empty shells. Shells of the non-indigenous bivalve Anadara demiri were recorded for the first time in the Croatian part of the Adriatic Sea. In terms of biomass and abundance the dominant species were Acanthocardia tuberculata, Callista chione, Chamelea gallina, Glycymeris bimaculata, G. glycymeris, G. violascens, Laevicardium oblongum, Modiolus barbatus, Mytilus galloprovincialis, Ostrea edulis and Venus verrucosa. Statistically significant differences were noted in bivalve communities in the five main sampling areas including the island of Rab, Pag bay, Kaštela bay, Cetina estuary and Neretva estuary.Istraživanje zajednica školjkaša provedeno je tijekom 2007. i 2008. godine duž istočne obale Jadrana, od otoka Raba na sjeveru do ušća rijeke Neretve na jugu. Glavni cilj istraživanja bio je opis raspodjele i strukture zajednica školjkaša na mekim dnima duž istočne obale Jadrana, sa posebnim naglaskom na gospodarski važne vrste školjkaša u pet glavnih izlovnih područja. Hidrauličnom dredžom prikupljeno je ukupno 105 uzoraka na dubinama od 1 do 11 m. Prikupljeni školjkaši na terenu su odvojeni i zamrznuti za daljnju laboratorijsku analizu koja je uključivala identifikaciju vrsta te analizu brojnosti i biomase. U prikupljenim uzorcima 54 vrste školjkaša bile su zastupljene sa živim primjercima, dok je iz ljušturnih ostataka identificirano 87 vrsta školjkaša. Ljušture alohtone vrste školjkaša Anadara demiri zabilježene su po prvi puta u hrvatskom dijelu Jadrana. Maseno i brojčano najzastupljenije vrste bile su: Acanthocardia tuberculata, Callista chione, Chamelea gallina, Glycymeris bimaculata, G. glycymeris, G. violascens, Laevicardium oblongum, Modiolus barbatus, Mytilus galloprovincialis, Ostrea edulis i Venus verrucosa. Statistički značajna razlika zabilježena je u zajednicama školjkaša na pet glavnih područja istraživanja uključujući otok Rab, Paški zaljev, Kaštelanski zaljev te ušća rijeka Cetine i Neretve

Species composition, seasonal fluctuations, and residency of inshore fish assemblages in the Pantan estuary of the eastern middle Adriatic

A total of 9434 fishes, mainly juveniles, belonging to 15 families and 42 species were caught at six stations in the Pantan estuary in the eastern mid Adriatic. Using a 50 m beach seine, 1493 specimens of 25 species were caught in summer, 2594 specimens of 26 species in autumn, 3626 of 24 species in winter, and 1721 of 30 species in spring. Seven species comprised 87.8% of the total: Atherina boyeri (33.2%), Pomatoschistus marmoratus (28.1%), Liza aurata (8.3%), Liza ramada (7.1%), Aphanius fasciatus (5.5%), Diplodus annularis (2.9%) and Mugil cephalus (2.6%). An ANOSIM2 test for unreplicated 2-way layouts revealed significant differences in species assemblages among the sites (ρav = 0.385, P = 0.007). Stations with similar hydrographic conditions had similar species richness and assemblages. Statistically significant differences were not noted between seasons (ρav = 0.221, P = 0.057) although some seasonal differences, especially between summer and winter, were observed on nMDS plots. The most important ecological category was planktivorous fishes (39.4%), followed by benthic mesocarnivorous fishes (33.9%), and particulate organic matter feeders (21.3%). Twenty-two species were permanent estuary residents, 14 opportunists, and six transients. This study demonstrates that the Pantan estuary is an important fish nursery habitat that, although small, has great spatial fish diversity and therefore deserves special protection

Ciclo reproductivo de Glycymeris nummaria (Mollusca: Bivalvia), de la bahía de Mali Ston, Mar Adriático, Croacia

The reproductive cycle of the dog cockle, Glycymeris nummaria (Glycymerididae), was studied using specimens collected monthly from Mali Ston Bay, southeastern Adriatic Sea over the period from January to December 2010. We analysed sex ratios, gonad developmental stages, and oocyte diameters using standard histological techniques. There were no differences in the overall sex ratio and no difference in shell length with respect to sex. Results of a size-frequency analysis of oocyte diameters agreed with a qualitative analysis of gonadal developmental stages, confirming the occurrence of one annual spawning peak from May to July. A significant correlation was identified between mean gonad indices of males and females and condition index. This study provides the first data on the reproductive characteristics of G. nummaria, providing necessary information for the future sustainable management of its potential fishery.El ciclo reproductivo del bivalvo Glycymeris nummaria (Glycymerididae) fue estudiado en base a especímenes recolectados mensualmente entre enero y diciembre de 2012 en la Bahía Mali Ston (sudeste del Adriático). Analizamos la proporción sexual (sex ratio), los estadios del desarrollo gonadal y el diámetro de los ovocitos utilizando las técnicas histológicas estándares. No existen diferencias en la proporción sexual ni tampoco en la longitud de los especímenes en relación al sexo. Los resultados del análisis de la frecuencia de los diámetros de los ovocitos concordaron con el análisis cualitativo del estadio de desarrollo de las gónadas, confirmando la existencia de un pico de puesta anual entre los meses de mayo y julio. Asimismo se encontró una correlación significativa entre los índices gonadales promedio de machos y hembras y el índice de condición. Este estudio aporta por primera vez datos de las características reproductivas de G. nummaria que son necesarios para la gestión sostenible de la pesca potencial de esta especie en un futuro

Shellfish Diseases

Školjkaši zauzimaju sve značajniji položaj u suvremenoj prehrani, a time i u gospodarstvu. Intenziviranjem proizvodnje pojavljuju se zdravstveni problemi unutar samih uzgojnih populacija, a u nekim je slučajevima ugroženo i zdravlje krajnjeg potrošača. U tekstu su opisani različiti uzročnici bolesti na uzgajalištima, njihovi putevi djelovanja i moguće mjere za suzbijanje širenja bolesti. Također su navedene potencijalne opasnosti za ljudsko zdravlje.Significance of the shellfish as food increases, as well as its importance on the market. Intensive production causes health hazards inside shellfish populations. In some cases even consumers health is affected. This paper describes causative agents of shellfish diseases, spreading paths and prevention. Potential hazards for human health are also noted

Fuentes potenciales de alimento en Glycymeris nummaria (Mollusca: Bivalvia) durante el ciclo anual a partir del análisis de ácidos graso

Seasonal changes of food sources were investigated by analysing the fatty acid profiles of digestive gland and muscle tissues of the naturally occurring clams Glycymeris nummaria in Mali Ston Bay, Croatia. Total lipids in the digestive gland and the adductor muscle showed parallel changes, with a maximum after the main spawning event in September. In the digestive gland saturated fatty acids were highly dominant (up to 82%), indicating detritus as the main food source for this species. This type of food prevailed during the autumn/winter period, in contrast to the spring/summer period when detritus was enriched with phyto- and, to a lesser extent, zooplankton. Fatty acid composition of muscles indicated highly efficient utilization of ingested food through significant retention of polyunsaturated fatty acid from the clams’ diet during the entire period investigated.Se han investigado los cambios estacionales en las fuentes de alimentación de poblaciones naturales del bivalvo Glycymeris nummaria en la bahía Mali Ston (Croacia) por medio del análisis de los perfiles de ácidos grasos de la glándula digestiva y del tejido muscular. El total de lípidos tanto de la glándula digestiva como en el músculo aductor mostró cambios similares después del principal evento de freza (septiembre). En la glándula digestiva los ácidos grasos saturados fueron altamente dominantes (hasta el 82%), lo que señala a los detritos como principal fuente de alimentación de esta especie. Este tipo de alimento prevalece durante el otoño/invierno, mientras que en primavera/verano la alimentación se complementa con fitoplancton y, en menor medida, con zooplancton. La composición de ácidos grasos en el tejido muscular indica una alta eficiencia en la utilización del alimento ingerido mediante la retención de los ácidos grasos poliinsaturados (PUFA) de la dieta durante todo el periodo investigado