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Stone crayfish (Austropotamobius torrentium) is one of the four native European crayfish species inhabiting Croatian freshwaters and is protected by Croatian law. The aim of this work was to investigate several aspects of species life cycle, morphometrics and habitat preferences. Populations were studied for 18 months in two streams in the Karlovac County. Crayfish were trapped once a month. Altogether 806 crayfish were analysed and their weight plus 7 morphometric characteristics per crayfish were recorded. Eight different physicochemical parameters of the water were measured. We found positive correlations between the number of captured individuals and water temperature, conductivity and water hardness. A negative correlation was found between the number of captured individuals and water level. The maximal recorded weight was 72 g for males and 43 g for females, while the maximal recorded body length was 11.02 cm for males and 10.37 cm for females. Freshly moulted animals were caught from June to November. Development of the glair glands started in July, external eggs were recorded from November to June and newly hatched juveniles were caught in June and July. The smallest egg-bearing female was 6.42 cm long. Males and females differed significantly in all measured morphometric characteristics and body weight, while crayfish from the two populations differed significantly in carapace width, claw length, claw width and claw height in males and in total body length, carapace width, claw height and width of the first abdominal pleura in females. It could be assumed that observed morphological differences between populations occurred due to crayfish adaptation to specific local environmental and ecological conditions., Potočni rak (Austropotamobius torrentium) jedna je od četiri europske vrste deseteronožnih rakova iz porodice Astacidae koja živi u hrvatskim slatkovodnim ekosustavima te je strogo zakonom zaštićena. Cilj ovog rada bio je istražiti nekoliko aspekata životnog ciklusa vrste, njenu morfometriju i uvjete staništa. Populacije su istraživane tijekom 18 mjeseci u dva potoka u Karlovačkoj županiji. Životinje su lovljene jednom mjesečno. Ukupno je ulovljeno 806 jedinki kojima je zabilježen spol, faza presvlačenja i reprodukcije, izmjereno je sedam morfometrijskih obilježja i težina tijela. Pri svakom uzorkovanju izmjereno je osam fizikalno-kemijskih parametara vode. Zabilježena je pozitivna korelacija između broja ulovljenih jedinki i temperature, vodljivosti i ukupne tvrdoće vode. Negativna korelacija zabilježena je između broja ulovljenih jedinki i razine vode. Maksimalna zabilježena težina tijela iznosila je 72 g kod mužjaka i 43 g kod ženki, dok je maksimalna zabilježena dužina tijela iznosila 11,02 cm kod mužjaka i 10,37 cm kod ženki. Svježe presvučene životinje lovljene su od lipnja do studenog. Razvoj cementnih žlijezda započeo je u srpnju, vanjska jaja bilježena su od studenog do lipnja, a tek izlegli juvenilni rakovi zabilježeni su u lipnju i srpnju. Najmanja ženka s pleopodalnim jajima bila je duga 6,42 cm. Mužjaci i ženke razlikuju se značajno u svim mjerenim morfometrijskim obilježjima i težini tijela, dok se jedinke iz dviju populacija međusobno značajno razlikuju u širini karapaksa, dužini, širini i debljini kliješta kod mužjaka te ukupnoj dužini tijela, širini karapaksa, debljini kliješta i širini prve abdominalne pleure kod ženki. Možemo pretpostaviti da su zabilježene morfometrijske razlike između populacija posljedica adaptacije na specifične stanišne i ekološke uvjete.

Stone crayfish (Austropotamobius torrentium) is one of the four native European crayfish species inhabiting Croatian freshwaters and is protected by Croatian law. The aim of this work was to investigate several aspects of species life cycle, morphometrics and habitat preferences. Populations were studied for 18 months in two streams in the Karlovac County. Crayfish were trapped once a month. Altogether 806 crayfish were analysed and their weight plus 7 morphometric characteristics per crayfish were recorded. Eight different physicochemical parameters of the water were measured. We found positive correlations between the number of captured individuals and water temperature, conductivity and water hardness. A negative correlation was found between the number of captured individuals and water level. The maximal recorded weight was 72 g for males and 43 g for females, while the maximal recorded body length was 11.02 cm for males and 10.37 cm for females. Freshly moulted animals were caught from June to November. Development of the glair glands started in July, external eggs were recorded from November to June and newly hatched juveniles were caught in June and July. The smallest egg-bearing female was 6.42 cm long. Males and females differed significantly in all measured morphometric characteristics and body weight, while crayfish from the two populations differed significantly in carapace width, claw length, claw width and claw height in males and in total body length, carapace width, claw height and width of the first abdominal pleura in females. It could be assumed that observed morphological differences between populations occurred due to crayfish adaptation to specific local environmental and ecological conditions.

Astacus leptodactylus is one of four native freshwater crayfish inhabiting Croatian inland waters. Comparing data on its distribution from historical sources and recent research, it seems that narrow-clawed crayfish is spreading from the east to the west and south of Croatia. As little is known about its life cycle, therefore the aim of our research was to gather data on narrow-clawed activity throughout a year. The research was conducted in Dobra and Mrežnica rivers (continental Croatia). Crayfish sampling was carried out with baited LiNi traps twice a month, and different physiological crayfish functions and morphometrical characteristics were recorded, as well as physico-chemical parameters of the water. Altogether 311 crayfish were trapped (180 males, 131 females). Sex ratio fluctuated throughout the year, depending on their physiological cycle. The heaviest male was 113 g, and female 125 g, while the longest male was 14.78 cm, and female 16.71 cm. Animals were active all the year around, with the peak of activity in April and June. Preparation for mating started at the end of August and in September (developed glair glands and enlarged gonopods) and juveniles hatched in mid-May. Freshly moulted animals were found from mid-April until September. Main injuries were claw and limb loss, and there were no signs of diseases or epibionts within the studied populations. Correlation of crayfish activity and different physico-chemical parameters of water are discussed in details.

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.