Spatial dynamics of the noble crayfish (Astacus astacus, L.) in the Paklenica National Park

The aim of this work was to analyse the spatial dynamics of a noble crayfish population inhabiting the Velika Paklenica Stream (Paklenica National Park, Croatia). The study was conducted in July 2000, and between March and September 2002. Crayfish were trapped by baited LiNi traps and hand-made traps at two localities over 25 nights. We recorded the precise position of the captured crayfish, their sex, and total length. Crayfish were individually marked and then released back into the stream at the same spot where they were caught. Spatial analyses included determination of movement direction, distribution type, home range, total distance travelled, and mean daily movement. A mean home range of approximately 19 m was calculated. No difference in home range between the sexes was found. There was a large individual variation in the extent of movement without any effect of sex or size

THE RELATIONSHIP BETWEEN FEMALE SIZE AND EGG SIZE IN THE FRESHWATER CRAYFISH AUSTROPOTAMOBIUS TORRENTIUM

The aim of our research was to gather information about the reproduction cycle of Austopotamobius torrentium in Croatia. The research was conducted between October 1998 and April 2000 in streams on the Medvednica Mountain (north-west Croatia). We caught 767 females, of which 92 (11.99%) were berried. Berried females were captured from the beginning of November until mid June of the following year. Total length (from the tip of the rostrum to the end of telson) of the smallest female with pleopodal eggs was 5.40 cm, while the longest was 8.70 cm. Diameter of pleopodal eggs varied from 0.24 cm to 0.34 cm (mean ± SD = 0.28 ± 0.02) and their number per female from 1 to 104. Correlations between female size (total length and weight), number of pleopodal eggs and egg diameter were done. We found positive correlation between female length and number of eggs (r = 0.46) and between female length and egg diameter (r = 0.29), as well as between female weight and egg number (r = 0.50) and female weight and egg diameter (r = 0.30). Weak positive correlation was recorded between number of eggs and their diameter (r = 0.06)

Spatial dynamics of the noble crayfish (

The aim of this work was to analyse the spatial dynamics of a noble crayfish population inhabiting the Velika Paklenica Stream (Paklenica National Park, Croatia). The study was conducted in July 2000, and between March and September 2002. Crayfish were trapped by baited LiNi traps and hand-made traps at two localities over 25 nights. We recorded the precise position of the captured crayfish, their sex, and total length. Crayfish were individually marked and then released back into the stream at the same spot where they were caught. Spatial analyses included determination of movement direction, distribution type, home range, total distance travelled, and mean daily movement. A mean home range of approximately 19 m was calculated. No difference in home range between the sexes was found. There was a large individual variation in the extent of movement without any effect of sex or size

YEAR CYCLE OF AUSTROPOTAMOBIUS TORRENTIUM (SCHRANK) IN STREAMS ON MEDVEDNICA MOUNTAIN (CROATIA).

We studied life cycle of stone crayfish for 18 months in three streams on Medvednica Mountain, located above city of Zagreb. Sampling of animals was carried out with baited traps twice a month and various physiological functions were recorded. Sex ratio of trapped crayfish was 1:1, but it fluctuated during the year. Animals were active from early spring until the beginning of November when their activities significantly decreased. In this period we noticed three peaks of higher activity. The first one after winter starvation in March, the second one after egg hatching (June/July) and the third one during mating period (end of September - beginning of November). The maximal recorded weight for female was 38 g while the heaviest male was 55 g. The longest female was 9.28 cm and male 10.30 cm. Development of glair glands started from the end of July, mating occurred at the end of October and the juveniles hatched until mid-June. Freshly moulted animals were found from mid-May until mid-October. Main injuries were claw and limb loss. We noticed the presence of burn spot disease and Branchiobdella parasita Henle within studied populations. Correlation with five different physico-chemical parameters of water showed that animals’ activity is positively correlated to water temperature, conductivity, pH and hardness and negatively to oxygen concentration

Occurrence of Branchiobdellida (Annelida : Clitellata) on freshwater crayfish in Croatia

There is very little information on the genus Branchiobdella and the species relationships with their freshwater crayfish hosts in Croatia. Therefore, a base-line study was needed so that future changes in available habitat brought about by urban development and the probable introduction of non-native species can be accurately assessed. This investigation used preserved freshwater crayfish collected from across Croatia between 1995 and 2005 as its source of the ectosymbionts. Crayfish species included Astacus astacus, A. leptodactylus, Austropotamobius pallipes, A. torrentium, and the allochtonous North American species, Orconectes limosus. Only native European species of branchiobdellids were found: Branchiobdella astaci, B. parasita, B. pentodonta, B. hexodonta, B. italica, and B. balcanica, and this is the first report on the occurrence of these species, apart from B. italica, in Croatia. The distribution of these branchiobdellidans is compared with climatic and river drainage systems, and literature reports of populations in other countries in the region