Nikša Glavić

Incidence of spinal deformities in natural populations of sandsmelt, Atherina boyeri (Risso, 1810) in the Neretva river estuary, middle Adriatic

Information is presented on the occurrence of spinal deformities in natural populations of sandsmelt, Atherina boyeri in the Neretva River estuary, middle eastern Adriatic. During 1998 and 1999, the spinal deformity levels varied between 2.02% and 10.30% in four samplings, and 3.58% in total catch. The spine is deformed in one to a few places from vertical to horizontal angles, and the deformities are visible on the fish body immediately after catching. The possible reasons for such deformities are discussed.

Preliminary information on feeding and growth of pompano, Trachinotus ovatus (Linnaeus, 1758) (Pisces ; Carangidae) in captivity

Although the chances of successfully farming Trachinotus ovatus on a commercial scale are limited by the low food conversion rates, this species deserves further applied studies on the basis of their quick adaptation to confinement and their tolerance of captivity conditions.

The spawning, embryonic and early larval development of the green wrasse Labrus viridis (Linnaeus, 1758)(Labridae) in controlled conditions

Green wrasse, Labrus viridis (Linnaeus, 1758), is an endangered species in the southern Adriatic Sea, but it is also of interest for potential rearing in polyculture with other commercial species for the repopulation of areas where it is endangered or as a new aquaculture species. A parental stock of the green wrasse was kept in aquaria for six years. The spawning, embryonic and early larval development maintained under controlled laboratory conditions are described and illustrated. The average diameter of newly spawned eggs was 1.01±0.03 mm. Mature and fertilized eggs were attached to the tank bottom by mucus. Hatching started after 127 h at a mean temperature of 14.4±0.8°C. The average total length of newly hatched larvae was 4.80±0.22 mm. Absorption of the yolk-sac was completed after the 5th day when larvae reached 5.87±0.28 mm. Larvae were fed with the rotifers Brachionus plicatilis. The pigmentation of L. viridis larvae is similar to that of Labrus merula and Labrus bergylta, but the main differences between these species are in the size of larvae and the development time of the melanophores on the anal fin-fold (five days later than with L. merula) and on top of the head (nine days earlier than with L. merula).

Ecological characteristics of plant species and associations along two Dinaric karstic rivers (Bosnia and Herzegovina, the Balkans)

This paper describes the plant communities of two oligotrophic karstic rivers with a slight anthropogenic influence — the Trebižat and the Lištica — in South Bosnia and Herzegovina, their sinecology, and the relationship between vegetation and plant species and environmental parameters. According to 87 relevés, a total of 26 plant associations, using Braun-Blanquet methods, were found in the rivers and nearby surveyed area. Only nine associations were common to both rivers. Eight associations were recorded for the territory of Bosnia and Herzegovina for the first time. Associations from both rivers differed according to following parameters measured at the sampling site: water temperature, distance from the mouth (river kilometers), river width, water depth, flow, pH and slope. There were no differences in nutrient concentrations among the associations. According to Canonical Correspondence Analysis (CCA), three environmental variables out of the 11 initially considered were retained as being related to plant distribution. The first two axes explained 56.8% and 35.2% of variance of species-environment relationship in the Trebižat and Lištica rivers, respectively. Water depth in the Trebižat River, and pH and river kilometers in the Lištica River were found to be the most influential, while nutrients and other physico-chemical parameters were not significant in either river. Water depth vector was identified as an underlying environmental factor determining distribution of Potamogeton lucens and Myriophyllum verticillatum (Potamion), and Nymphaea alba (Nymphaeion albae). According to in situ measurements of light intensity, the highest coefficients of light attenuation, radiance and reflection were found at a station with dense populations of Potamogeton lucens and Nuphar luteum (Potametum lucentis). The vegetation and floristic value of the rivers is discussed as a basis for biodiversity conservation programmes and evaluating the state of these ecosystems in the future.

IMPACT OF OOCYTE SIZE ON LHRHa INDUCEDOVULATION AND FERTILIZED EGG QUALITY IN SADDLED BREAM OBLADA MELANURA (LINNAEUS, 1758)

The objective of this study was to evaluate the effects of oocyte size and luteinizing hormone releasing hormone analogue (LHRHa) on ovulatory success in artificial fertilization. Vitellogenic females with maximum oocyte diameters 400-550 μm were repeatedly injected with LHRHa (20 μ g kg-1 per injection). Fish with maximum oocyte diameters 500 μm spawned within 48-54 h. These results demonstrate that injected LHRHa is effective for ovulation of saddled bream with maximum oocyte diameters >500μm.