Selçuk Berber

Seasonal variation in the condition index, meat yield and biochemical composition of the flat oyster Ostrea edulis (Linnaeus, 1758) from the Dardanelles, Turkey

This study was conducted in Dardanelles between October 2007 and August 2009 when condition index, meat yield, biochemical compositions and environmental parameters of seawater were investigated and the study area was found to have available conditions for cultivation. Investigation of the study area showed a positive correlation in particular among condition index, seasonal variation of temperature, protein, fat and chlorophyll-a; a negative correlation was seen between them and carbohydrate value. It was clear from the two years study that the most ideal period for oyster harvest is April and August especially when condition index was maximum followed by a winter with no oyster yield is available in terms of the related processes involving oyster cultivation.

Reproductive efficiency of the narrow-clawed crayfish, Astacus leptodactylus , in several populations in Turkey

Studies were carried out to evaluate the reproductive efficiency of the narrow-clawed crayfish, Astacus leptodactylus Eschscholtz, 1823, in three different populations in the lakes Apolyont, Iznik, and Manyas in Turkey. Crayfish were sampled monthly using fyke-nets of 34 mm mesh size from April 2002 until March 2003. The average number of pleopodal eggs (with their range), per female, was 200 ± 12 (8-556) in Lake Apolyont, 202 ± 13 (6-350) in Lake Iznik, and 257 ± 13 (18-465) in Lake Manyas. The average number of ovarian eggs (with their range), per female, was 348 ± 20 (126-630) in Lake Apolyont, 305 ± 11 (162-465) in Lake Iznik, and 400 ± 18 (205-776) in Lake Manyas. The average egg diameter and ranges were 2.23 ± 0.004 (1.80-2.98) mm in Lake Apolyont, 2.53 ± 0.003 (2.06-2.92) mm in Lake Iznik, and 2.65 ± 0.027 (1.98-3.04) mm in Lake Manyas. Neither egg diameter nor egg weight increased with body size, but the variability of egg size and weight was high. No relationship was found between egg size and female crayfish size for any of the lakes. Mean size at maturity of female A. leptodactylus varied among the lakes. Females in Apolyont populations reached sexual maturity at a size of 64.3 mm TL, but spawning occurred only when females attained 82-128 mm TL, indicating that the mean minimum reproductive size was 82 mm TL in Lake Apolyont. Average female size was 88.7 mm (±SD 0.6; max. 142 mm; min. 48 mm; n = 154). In Iznik Lake, size at maturity of females was 78 mm TL, while spawning size was 83142 mm TL; average female size was 90.6 mm (±SD 0.5; max. 139 mm; min. 66 mm; n = 99). Finally, female size at maturity was 72.6 mm TL, and spawning size was 80-130 mm TL in Manyas Lake; average female size was 89.0 mm (±SD 1.1; max. 141 mm; min. 29 mm; n = 122). The total observed sex ratio (male/female) was found to be 1.00/0.53 in all three lakes together. Mature A. leptodactylus reproduce only once a year under natural conditions. No evidence was found in this study to suggest the occurrence of multiple spawnings.

Relationships of benthic amphipod communities with environmental variables in the shallow waters of the Dardanelles

The structure of the benthic amphipod assemblage and its relationship with soft-bottom characteristics (particle size, organic matter, etc.) of the coastal waters at the depths of 0–5 m at the Dardanelles, including the Turkish Straits System, was studied. A SCUBA diver took benthos and sediment samples seasonally using a quadrate system of 30×30 cm as three transects from the 8 different stations between July 2008 and April 2009. A total of 3007 individuals belonging to 50 species was reported. Among these, Corophium acutum Chevreux, 1908 had the highest dominance value (Di%=22.18) and the lowest dominance value belonged to Dexamine thea Boeck, 1861 (Di%=0.03). The highest positive correlation (rs=0.57, p<0.05) was observed between the gravel content (%) and the abundance (ind. m−2). The highest sand rate (99.59%) in the sediment was found at the Eceabat site. The lowest rate was at the Kepez Harbour station with a value of 73.01%. The highest H′ value (1.53) was recorded at the Eceabat site, and the lowest H′ value (H′=0.95) was recorded at the Gallipoli sampling station.

A Study on the Relationships between Some Morphological and Reproductive Traits of the Turkish Crayfish, Astacus leptodactylus Eschscholtz, 1823 (Crustacea: Decapoda)

This study was carried out to investigate relationships between some morphological and reproductive traits of the Turkish crayfish, A. leptodactylus, collected from a controlled irrigation lake in the Yenice province (Çanakkale, Turkey), between July 2007 and June 2008. For this objective, two multivariate analysis techniques, namely canonical correlation analysis and multivariate multiple linear regression analysis, were used. The results of the canonical correlation analysis have shown that the morphological traits may be used to predict the changes in the reproductive traits. For instance, canonical correlation analysis results suggested that the egg weight and the number of eggs are related to the total length, carapace length, and carapace width. The results of multivariate multiple linear regression analysis, on the other hand, show a slightly different picture. Therefore, it is possible to conclude that both canonical correlation and multivariate regression results can be taken into consideration together when investigating the relations between two variable sets.

Zebra midyesinin (Dreissena polymorpha'nın (Pallas, 1771)) Türkiye'nin bazı su kaynaklarında yaşayan dar kıskaçlı kerevitler üzerinde ilk olarak gözlenmesi

Zebra midyeleri, Dreissena polymorpha (Pallas, 1771) hidroelektrik ve nukleer guc sistemlerinde su akisini engellediginden zararli bir istilaci epibiont turu olarak kabul edilir. D. polymorpha suyun temizlenmesi, su gorunurlugunun arttirilmasi ve kirleticilerin filtrelenmesi olarak rapor edilmesine ragmen, bazi baliklarin ve sucul turlerin populasyonu ve buyuklugu uzerinde olumsuz etkilere sahiptir. Bu calismada, zebra midyesi Turkiye’deki bazi su kaynaklarindaki tatlisu istakozu uzerinde ilk defa gozlemlenmistir. Bireyler Turkiye’deki iki dogal gol (Cildir Golu, Egirdir Golu) ve bes goletten (Altinyazi Baraj Golu, Keban Baraj Golu, Kucukcekmece Golu, Karpuzlu Baraj Golu, Kadikoy Baraj Golu) toplanmistir. Bu calismada, kerevitlerin farkli vucut bolumlerine zebra midyesinin tutunmasi belgelenmistir. Cochran’s Q test sonuclari; kerevitin degisik bolumlerine tutunan midye sayilarinin farklilik gosterdigini ortaya koydu (P=0.000) (P <0.001). Zebra midyelerin tatlisu istakozlarinin uzerinde tutunma bolgeleri arasinda farkliligin tespit edilmesinin konakci acisindan bazi olumsuzluklara neden olabilecegi dusunulmektedir. Ozellikle carapax bolgesinde yogun tutunmalarin; hareket (beslenme, ciftlesme, predatorlerden kacinma ve barinma). Pleopodal bolgedeki midye bireyleri ise yumurta tutunumu ve tasinimini zorlastirabilir. Bu calisma Turkiye sularindaki Astacus leptodactylus uzerinde Dreissena polymorpha ’nin varligi ile ilgili ilk rapordur.