This study deals with temporal variations in eel Anguilla anguilla diet, sampled seasonally in the Languedocian Mauguio lagoon (Gulf of Lion), from Autumn 1998 to Summer 1999. Eel mainly feeds on ...benthic organisms, primarily small Amphipoda, Crustacea (mainly Gammarus gr. locusta), Polychaeta, insect larvae (Chironomidae) and small fish. Based on variations in the eels feeding regime, seasonal influence is illustrated by decreased feeding activity in summer, which progressively increases during the following seasons. The trophic quality available to eels in the Mauguio lagoon depends more on allochtonous inputs from the catchment area than on its own hydrodynamics on which water of marine origin has little influence due to its long distance from the sea. Variations observed during the four seasons illustrate the opportunist type feeding behaviour of eels. They consume the most available benthic preys at a given moment without using a particular feeding strategy like specialisation or generalisation. Eel adapts its diet according to the available resources offered by the ecosystem. Because of this eel, as an amphihaline migrant species, can be characterised as an obvious indirect bioindicator of the trophic capacity and very marked level of confinement in the brackish lagoon ecosystem of Mauguio.Original Abstract: U ovom radu se raspravlja o vremenskim kolebanjima u prehrani jegulje Anguilla anguilla, koja je uzorkovana sezonski u laguni Mauguio pokrajine Languedoc u Lionskom zaljevu, od jeseni 1998. do ljeta 1999. Jegulja se hrani bentoskim pridnenim organizmima, i to pretezito manjim rakuscima (poglavito Gammarus gr. locusta), mnogocetinasima, larvama insekata (Chironomidae) i manjim ribama. Temeljem varijacija u prehrambenom rezimu jegulje sezonski utjecaj pokazuje da hranidbena aktivnost opada u ljeto, dok progresivno raste u ostalim godisnjim dobima. Troficka kvaliteta dostupna jeguljama u laguni Mauguio ovisi vise o alohtonom unosu iz slivnog podrucja nego o vlastitoj hidrodinamici na koju morska voda ima malo utjecaja zbog njenog dugog mijesanja s morem. Zapazena kolebanja tijekom cetiri godisnja doba ukazuju na oportunisticki tip prehrambenog ponasanja jegulje. Ona se hrani najdostupnijim bentoskim organizmima u datom trenutku bez ikakve prehrambene strategije kao sto je su to specijalizirana ili generalizirana prehrambena strategija. Jegulje prilagodavaju svoju prehranu prema dostupnoj hrani unutar ekosustava. Stoga se jegulja kao migracijska vrsta moze biti okarakterizirana kao ociti indirektni bioindikator trofickog kapaciteta i vrlo znacajnog nivoa ogranicenja u ekosustavu bocate lagune Mauguio.
An abnormal partially-albino embryo with atypical characteristics was removed from a pregnant female sandbar shark, Carcharhinus plumbeus, caught in the Gulf of Gabes in southern Tunisian, central ...Mediterranean. The specimen is described and atypical characteristics and albinism in shark species is reviewed.Original Abstract: Neuobicajeni embrio s atipicnim obiljezjima, djelomicno albino, koji je odstranjen iz skotne zenke psa tupana, Carcharhinus plumbeus uhvacen je u Gabeskom zaljevu (juzni Tunis), centralni Mediteran. U ovom radu opisan je nadjeni primjerak. Dat je pregled atipicnih obiljezja i albinizma ove vrste morskog psa.
The sandbar shark, Carcharhinus plumbeus, is commonly captured in the Gulf of Gabes (southern Tunisia). Of 932 specimens collected from January 2001 to May 2004, the smallest mature male was 1545 mm ...total length and the largest male was 1935 mm. All males above 1600 mm were mature. Adult females ranged 1660-2815 mm, while all females above 1720 mm were mature. The pupping season occurred in spring and early summer, with parturition in July. Gestation was estimated at twelve months, with females appearing to reproduce in alternate years. The diameter of the largest yellow-yolked oocytes ranged 29-32 mm (mean 30.3 plus or minus 1.2) with the mass ranging 9.1-13.3 g (mean 11.9 plus or minus 1.3). Both uteri were compartmentalized into chambers and a single embryo developed in each chamber. Length and weight at birth, based on near-term embryos, were estimated at 450- 650 mm and 532-1458 g. The chemical balance of development, based on the mean dry masses of the largest yellow-yolked oocytes and near-term embryos, was 40.3, showing that C. plumbeus is a matrotrophic species. Ovarian fecundity was slightly higher than uterine fecundity. There was a positive relationship between uterine fecundity and total length of females. Litter sizes ranged 4-10 (mean 6.9 plus or minus 1.1). Embryos and free-swimming juvenile and adult females significantly outnumbered males.Original Abstract: Pas trupan siljokrilac, Carcharhinus plumbeus, redovito se lovi u Gabeskom zaljevu (juzni Tunis). Od 932 primjerka, sabrana od sijecnja 2001 do svibnja 2004, najmanji zreli muzjak bio je dug 1545 mm, a najveci 1935 mm. Svi muski primjerci, duzi od 1600 mm, bili su spolno zreli. Odrasle zenke bile su duge od 1660 do 2815 mm, od kojih su one preko 1720 mm duzine, bile spolno zrele. Sazrijevanje se odvijalo u proljece i rano ljeto, s okotom u srpnju. Vrjeme nosenja je procijenjeno na 12 mjeseci. Zenke su se razmnozavale u izmjenicnim godinama. Promjer najvecih oocita (sa zumanjcem) iznosio je 29-32 mm (prosjecno 30,3 plus or minus 1,2) i mase 9,1-13,3 g (prosjecno 11,9 plus or minus 1,3). Uterusi su bili pregradjeni u komorice. U svakoj komorici razvijao se samo po jedan embrij. Duzina i tezina kod rodjenja, bazirane na embrijima priblizno iste starosti, procijenjene su na 450-650 mm i 532-1458 g. Kemijska ravnoteza razvoja, bazirana na srednjim suhim tezinama zrelih oocita i embrijima priblizno iste starosti, iznosila je 40,3 sto znaci da je pas trupan siljokrilac, Carcharhinus plumbeus, matrotrofna vrsta. Plodnost ovarija bila je nesto veca od fekunditeta uterusa. Dobiven je pozitivan odnos izmedju fekutnditeta uterusa i totalne duzine zenki. Broj izleglih mladih bio je 4-10 (srednjak 6,9 plus or minus 1,1). Embriji i slobodno plivajuce odrasle zenke znatno su nadmasivale muzjake.
The milk shark, Rhizoprionodon acutus (Rueppel, 1837), is the shark species most abundantly landed at fishing sites along the Senegalese coast in the eastern tropical Atlantic. Adult males and ...females were mainly captured from March to September. The smallest adult male was 840 mm total length (TL) and weighed 2650 g; all males above 950 mm TL were adult. The smallest adult female was 890 mm TL and 4800 g; all females above 1000 mm were adult. The largest male and female were 1215 mm and 1260 mm TL and 6700 g and 6830 g, respectively. There was a significant difference in the total mass vs. TL relationship between males and females. Parturition and mating occurred in May and June. Gestation lasted approximately one year. Females had an annual reproductive cycle although some reproduced in alternate years. The diameter and mass of the largest yolked oocytes ranged 20-23 mm (mean 21.2 plus or minus 0.9) and 4.1-5.6 g (mean 4.8 plus or minus 0.5). Both uteri were compartmentalized into chambers with a single embryo in each chamber. Size and mass at birth, based on term embryos and neonates, ranged 325-500 mm TL (mean 391.4 plus or minus 24.4) and 127-350 g (mean 220.7 plus or minus 37.9). A chemical balance of development based on mean dry mass of the largest yolked oocytes and term embryos was 23. Ovarian fecundity was slightly higher than uterine fecundity. There was a slight positive relationship between uterine fecundity and female TL, but not between ovarian fecundity and female TL. Litter sizes ranged from one to eight (mean 3.5 plus or minus 1.3) with males and females equally distributed. In free-swimming specimens, females significantly outnumbered males, especially among sub-adult and adult specimens.Original Abstract: Morski pas, Rhizoprionodon acutus (Rueppel, 1837), je najvise rasprostranjen na ribarskim postajama duz senegalske obale istocnog dijela tropskog Atlantika. Odrasli muzjaci i zenke su pretezito lovljeni od ozujka do rujna. Ukupna duljina (TL) najmanjeg primjerka muzjaka iznosila je 840 mm, a tezina 2650 g, dok su svi odrasli muzjaci bili duzi od 950 mm TL. Najmanja odrasla zenka bila je duga 890 mm TL i teska 4800 g, a sve odrasle zenke bile su duze od 1000 mm. Najveci primjerak muzjaka bio je dug 1215 mm i tezak 6700 g, a najveci primjerak zenke bio je 1260 mm dug i 6830 g tezak. Ustanovljena je statisticki znacajna razlika izmedju odnosa mase i ukupne duljine (TL) kod muzjaka i zenki. Parenje i porod se odvijaju u svibnju i lipnju. Trudnoca je trajala oko godinu dana. Zenke su imale godisnji reproduktivni ciklus iako su se neke razmnozavale u naizmjenicnim godinama. Promjer najvece oocite sa zumanjcem iznosio je 20-23 mm (prosjek 21.2 plus or minus 0.9), a tezina je kolebala izmedju 4.1-5.6 g (prosjek 4.8 plus or minus 0.5). Oba uterusa bila su podijeljena u komorice i u svakoj od komorica razvijao se po jedan embrij. Duzina i tezina kod rodjenja, mjerena na embrijima i novorodjenim primjercima procijenjene su na 325-500 mm TL (prosjek 391.4 plus or minus 24.4) i 127-350 g (prosjek 220.7 plus or minus 37.9). Kemijska ravnoteza razvoja, temeljena na prosjecnoj suhoj tezini najvecih oocita sa zumanjcem i embrijima bliskog vremenskog razdoblja, bila je 23. Ovarijska plodnost bila je veca od uterine plodnosti. Ustanovljen je pozitivni odnos izmedju uterine plodnosti i ukupne duljine zenki, ali takav odnos nije ustanovljen kod ovarijske plodnosti i ukupne duljine (TL). Velicine izlegnutih mladih kolebale su od 1 do 8 (prosjek 3.5 plus or minus 1.3) podjednako kod muzjaka i zenki. Opcenito je bilo vise zenki nego muzjaka, narocito medju slobodno plivajucim odraslim primjercima.
The school shark, Galeorhinus galeus, is commonly captured off the Maghreb shore along the Algerian and Tunisian coasts of the southern Mediterranean. Of 517 specimens collected during more than ...twenty years, the smallest adult male was 1225 mm total length (TL) and weighed 11 580 g, the largest adult male was 1580 mm and weighed 18 000 g, and the heaviest male was 1570 mm and weighed 19 900 g. All males above 1260 mm TL were adult. Adult females were 1400-1900 mm TL. The smallest pregnant female was 1400 mm TL and carried developing embryos. The largest female was 1990 mm TL and weighed 27 900 g. Females were generally heavier than males, but there was no significant difference between males and females in mass versus total length relationship. Two ovulation and two pupping seasons occurred in winter and in spring. Gestation was estimated at twelve months, with most females appearing to reproduce in alternate years. The diameter of the largest yolky oocytes ranged 43-47 mm (mean 44.7 plus or minus 1.8) and the mass ranged 45-52 g (mean 47.9 plus or minus 2.2). Both uteri were compartmentalized into chambers and a single embryo developed in each chamber. Length and weight at birth, based on near-term embryos, were estimated at 240-320 mm TL and 88-109 g. The chemical balance of development, based on the mean dry mass of the largest yolky oocytes and of near-term fetuses, was about 1, showing that G. galeus can be considered as an incipient histotrophic species. Ovarian fecundity was higher than uterine fecundity. Litter sizes ranged 8-41. Males generally outnumbered females, especially among free-swimming adult specimens.
A nine-ocellated Torpedo torpedo, caught off the Languedoc coast in southern France (northern Mediterranean) is described in this paper. This is the greatest number of ocellae recorded to date in ...this species.Original Abstract: U ovom radu se opisuje primjerak drhtulje, Torpedo torpedo iz obalnih voda Laguedoc-a (juzna Francuska, sjeverni Mediteran) koja je imala 9 pjega sto je do sada za ovu vrstu najveci zabiljezeni broj.
Observations conducted over two years on nursehounds, Scyliorhinus stellaris, in captivity provided data on the number of eggs laid per year, embryonic development, size at hatching, length growth ...following hatching, and estimated fecundity.Original Abstract: Preko dvije godine su vrsena opazanja na macki mrkulji Scyliorhinus stellaris u kaptivitetu. Dobiveni su podaci o godisnje izleglom broju jaja, embrionalnom razvoju, velicini kod lezenja, rastu duzine nakon lezenja i procjeni plodnosti.
The Thau lagoon differs from other mediterranean lagoon sites in the apparent complexity of its benthic community structures, which seem to result from the relative complexity of its physical ...environment. A statistical analysis of the relationship between the abundances and biomasses of benthic taxa and the lagoonal hydrodynamic characteristics was carried out. An ACE-type statistical algorithm is used to expose the non- linear relationships in multiple regressions. Polychaete and crustacean biomasses along with mollusc densities at 15 sampling stations are considered as dependent variables. The granulometric fraction of the sediment below 40 μ as well as hydrodynamic descriptors such as kinetic energy and the exchange term$H^2V^2$, resulting from a numerical modeling of circulation forced by stochastic winds, are considered as predictors. The results demonstrate that the exchanges resulting from the hydrodynamic conditions within the watermass have a dominant beneficial influence on the development of each of the zoological groups considered. In addition, the importance of the sedimentary substrate is confirmed, but gives an interesting non-linear result, with a threshold between 3 and 6% of the fraction of fine particles below 40 μ. Apart from the quantification of this sedimentological indicator it appears that the dominant influence of the hydrodynamic exchange processes throughout the lagoon on the development of the benthic biological structures, quite independently of any bathymetric considerations, could give a new insight into the spatial organization of benthic communities in lagoonal ecosystems.
A quantitative and qualitative study of solid and dissolved waste output was carried out in relation to stocking density, through the study of nitrogen budgets in
Penaeus stylirostris rearing ponds. ...Stocking densities ranged from 1 to 30 shrimp m
−2. The nitrogen budget was determined, taking into account the different forms of nitrogen in the water (particulate, dissolved inorganic, dissolved organic), in the sediment, in the feed pellets, and in shrimps. Relationships were established between growout, stocking density, quantities of waste generated in ponds, characteristics of outflow and of sediment. Shrimp reared at different stocking densities showed different growth performances. At the end of the rearing cycle, shrimp reared at 1 m
−2 and at 30 m
−2 weighed 39.2±4.3 g and 16.8±2.4 g respectively. The quantity of wastes generated was proportional to the stocking density. Rearing one kg shrimp generated 60.8 and 157.2 g waste-N (dissolved+solid), at 1 m
−2 and 30 m
−2 respectively. The accumulation of waste-N in the sediment increased with stocking density. At the lowest stocking density, the sediment acted as a `supplier' and not as an accumulator of nitrogen. The nitrogen budget shows that up to 38.4% of the nitrogen entering the ponds in the inflow and in feed pellets, may accumulate in the sediment. The calculated outputs due to diffusion to the atmosphere and to denitrification account for 9.7 to 32.4% of the total. An increase in the level of the pond floors during the rearing period, by from 0.50±0.28 to 4.54±0.73 cm, appears to have been related neither to input and sedimentation of solids (seston or feed pellets), nor to hydraulic erosion of the pond banks, but to an erosion produced by the swimming activity of the shrimps.
Within the framework of an environmental impact study of aquaculture activities in the coastal marsh of Mahajamba (North-Western Madagascar), an assessment of the environmental conditions existing ...prior to the onset of aquaculture activities (production began in October, 1993) is essential. To this end, the area was mapped using SPOT-XS data, which made it possible to define the main ecodynamic tendencies of the mangroves before the development of the rearing ponds. The aim was then to implement fast, precise and reliable mapping methods, making it possible to follow mangrove alterations resulting from these aquaculture activities. Analysis of the radiometric behaviour of the various plant formations of the marsh, based on SIR-C radar data, revealed that the discrimination between these formations is easier when the frequency used is low and the polarization is crossed. Thematic analysis using textural classification was carried out with the L-band and polarization VH. The results generated are promising insofar as the mapping of mangroves is concerned with a fast treatment time and acceptable precision of the results.PUBLICATION ABSTRACT
