The ichthyoplankton of Izmir Bay: A one-year study of fish eggs and larvae

WOS: 000178687000008This study was carried out in order to determine the species diversity, abundance, and distribution and seasonal frequency occurrence times of the eggs and larvae of Teleost fish in Izmir Bay during 1989-1990. A total of 32140 eggs and 6582 larvae were collected from plankton samples and 69 species belonging to 27 families were identified. The most abundant families included Spariclae 23.79%, Clupeiclae 24.63%, Mullidae 12.22%, Serranidae 8.72% and Mugilidae 8.04% of total eggs, and Gobiidae 67.38%, Sparidae 9.43% and Blennidae 9.31% of total larvae. In this study, with regard to eggs, because some species preferred to release their eggs in clean water, stations in the outer bay showed similarities, while stations in the middle bay formed various groups amongst themselves. From the point of view of larvae, apart from station 2, which was near the lagoon area in the middle bay, the other stations were similar. The reason for this is the abundance of species of the Gobiidae family specific to that area. In areas with a low diversity index in respect of eggs, the presence of dominant species was detected. The highest diversity index and frequency of occurrence of fish eggs and larvae were determined in spring, the reason for this being that the spawning period of many fish species in Izmir Bay begins at the end of spring. In the middle and outer bay, where the stations in this study were situated, the pollution in Izmir Bay was found generally not to influence the species diversity of fish eggs and larvae

Some parameters of the population biology of spotted flounder (Citharus linguatula linnaeus, 1758) in Edremit Bay (North Aegean sea)

A total of 1096 spotted flounder (Citharus linguatula Linnaeus, 1758) were caught in Edremit Bay from September 1998 to September 2000. Length-weight relationships, age, growth, mortality and sex ratio of the samples were investigated. Within the population of this species, most of the individuals in our samples ranged from 100 to 160 mm (69.63%), the minimum and maximum total lengths of the specimens being 69 and 222 mm, respectively. Positive allometric growth was observed for male, female and all fish. Age distribution of the samples was from I to IV. There was no significant difference between observed and calculated (von Bertalanffy and back calculation) average total lengths of the age groups (P > 0.05). The sex ratio (females:males) was 1: 1.27. The total (Z), natural (M) and fishing mortality (F) rates, and the exploitation ratio (E) for all individuals were estimated respectively as Z = 0.60, M = 0.75, F = 0.15 and E = 0.25. This shows that the spotted flounder stock of Edremit Bay is being exploited at a lower than optimal level

Gulluk lagoon (Aegean Sea, Turkey) ecosystems [Gulluk lagunu (Ege Denizi, Turkiye) ekosistemi]

Gulluk Lagoon has an area of 2500 decares with a depth of 0.5-5.0 m and is connected to Gulluk Bay by a channel. In this study, samplings of phytoplankton and benthos were taken and physico-chemical parameters were recorded monthly during 1993 at 5 stations. The temperature reached a minimum of 10.42°C in January and a maximum of 26.9°C in July, with a mean annual temperature of 19.53±1.511. The salinity in the lagoon ranged from 7.48‰ to 13.92‰ in January and March, respectively with a mean annual salinity of 10.65 ± 0.555. Dissolved oxygen in the sub-surface (0.25 m) water was 5.56 mg 1-1 in June and 9.06 mg 1-1 in February, with an annual mean 7.31 ± 0.331. The Secchi-disk depth was 1.12 m in May and 2.40 m in October. Nutrient measurements revealed moderately high levels of ammonia (ranging from 4.39 to 29.70 µg-at 1-1), low nitrate (0.81 to 17.87 µg-at 1-1), nitrite (0.19 to 1.35 µg-at 1-1), phosphate (0.01 to 0.45 µg-at 1-1), and silicon (0.26 to 6.00 µg-at 1-1). Chlorophyll a distribution generally indicated that productivity was highest in May (21.49 mg 1-1) and lowest in September (0.77 mg 1-1). Melosira moniliformis was the predominant phytoplankton species. All of the stations were characterized by high species diversity. Identification of the benthic species was carried out with 60 samples collected from 5 stations in a of one year period. As result 68 benthi species belonging to 7 taxa (Nemertina, Polychaeta, Oligochaeta, Crustacea, Mollusca, Insecta, Echinodermata) were identified. The polychaetae were numerically dominated by Notomastus latericeus (3737 individuals), followed by Hediste diversicolor (1524 individuals), and Spionidae (sp) (1361 individuals). Economically important fish species in Gulluk Lagoon consist of mullets (Mugil cephalus, M. capito, Chelon labrosus, Liza saliens), Sparus aurata (gilthead sea bream), Dicentrarchus labrax (sea bass), Solea solea (sole), Anguilla anguilla (eel) and Cyprinus carpio (carp), with an annuall yield varying from 10 to 69 tonnes