FARMING AND RESTOCKING

One of the main objectives of RARITY is stock enhancing the native white clawed crayfish Austropotamobius pallipes in Friuli Venezia Giulia. Monitoring of the species carried out by the Ente Tutela Pesca (ETP) to undertstand have a detailed picture of the presence and abundancy of the indigenous river crayfish has outlined a general decrease and in some cases its conclusive disappearance. RARITY investigates the causes of this rarefaction and at the same time it takes care of the production of hatchery-reared juveniles in two hatcheries managed by ETP and the small A. pallipes individuals produced are then released into the nature. The two crayfish hatcheries are located in Savorgnano di San Vito al Tagliamento (Pordenone) and in Amaro (Udine), respectively. Project funds allowed for adjustement and renovation of the two facilities to make them produce about 30,000 native crayfish juveniles in the period 2012-2014. Dr Doctor Giorgio De Luise is the ETP consultant in charge of the coordination of production. In the past he had carried out experiments and similar production activities at the ETP fish farming plant of Flambro (Udine). The above mentioned previous experience and the engaging in discussions and sharing of opinion with other teams dealing with the production of hatchery-reared crayfish juveniles have leaded to the definition of specific production and restocking procedures easily learned and applied by ETP operators (see Didattica per gli operatori). Personnel assigned to crayfish hatcheries (partially volunteer and partially paid) attended a specific training course (see here for details) and has been also trained in the hatchery to fully learn the right production procedures. Production of crayfish juveniles is preceded by the genetic analysis of breeder populations (breeders are collected in the wild and brought back at the capture place at the end of production cycle). Restocking operations take mainly place into areas of the Natura 2000 net (Sites of Community Importance) where the small crayfish individuals (larvae L3) of A. pallipes are liberated. From 7.IX.2012 to 7.X.2013 4.928 juveniles have been released and within the end of October 2013 a total of more than 13.00 individuals will be liberated in the nature.


HATCHERIES

San Vito al Tagliamento (Pordenone)

This ETP crayfish hatchery consists of a small plant which has been used to hatch trout eggs untill the year 2011 (when RARYTY started). It is a small but functional facility located within a private property area in Savorgnano di San Vito al Tagliamento (Pordenone). The plant is covered and equipped with 10 fiberglass rectangular tanks (2.0x0.6 m) and 4 fiberglass circular tanks (diameter 1.5 m). Moreover, 4 rectangular tanks (2.1x0.60 m), 1 tank divided into 4 compartments (0.40x0.8 m) and 1 small artificial lake for the cultivation of aquatic plants are located outdoor. Tanks receive well water at a constant temperature of 12.4 °C. The hatchery is in operation for the project since November 2011 and it is fully managed by ETP volunteer personnel. This personnel carry out daily all farming operations (feeding, cleaning, checking, etc ...) and participates in the release of the juveniles and in the search and harvesting of breeders in the nature.


Amaro (Udine)

The hatchery of Amaro (Udine) is the second facility for the reproduction of A. pallipes and the production of hatchery-reared juveniles of the species for restocking purposes within the RARITY project. The plant is located close to Amaro (località Mulino Rainis) and has officially started to operate on September 2012. The production cycle takes place into 9 fiberglass rectangular tanks (six measuring 6.0x1.0 m and three 3.0x1.0 m) located into a sort of covered tunnel. Tanks receive well water at a constant temperature of 10.5 °C. Hatchery equipment also includes some tanks for quarantine and 2 concrete tanks (40.0x2.5 m) which can be divided in compartments for the cultivation of aquatic plants. This plant id totally managed by ETP employees.


FARMING

Farming

According to their specific use, the different hatchery structures have been assigned to sites for holding breeders divided by sex, scheduled matings, holding ovigerous females and the consecutive rearing of the larvae untill their release into the wild. Ovigerous females carrying eggs close to hatching are hosted in special perforated cages (delivery cages) equipped with a cover and suspended over the larval rearing tank (LRT) to allow for the newly hatched larvae to enter the underlying LRT and to start their life far from potential maternal predation behaviours. Breeders' tanks are equipped with artificial shelters consisting of PVC pipes and aquatic plants. LRTs are used to farm crayfish juveniles up to the size of 2.0 cm (when they are released in the nature) and they are equipped with artificial shelters consisting of peforated bricks located along the whole perimeter of the container and of several other refuges made of tunnels escavated into plastic materials, PVC leftover curls and again aquatic plants. Moreover, tanks are equpipped with one or more troughs consisting of little coloured plates where feed is placed. This allows for proper control and calibration of feeding avoiding or minimizing organic pollution of farming environment. All daily management operations are recorded tank by tank onto a dedicated sheet, and each single tank is equipped with a cleaning set and a small landing net. Crayfish diet consists of manifactured feeds (commercial pellets) characterized by a balance of nutrients matching the nutritional needs of crayfish and by a consistency giving the feed a long lasting time (no less than 48 h) into the water. Animals are fed daily 5% (breeders) or 1% (ovigerous females) of their biomass, or ad libitum (larvae). Aquatic plants (mainly of the genera Fontinalis and Elodea) and their micro- and macro- epifauna integrate the nutritional needs of farmed crustaceans. During their first week of independent life the larvae are fed nauplii of Artemia salina distributed ad libitum or commercial baby diets. The maturation of eggs resulted shortened within the farming plant in comparison to the natural environment and the first hatchlings have appeared at the beginning of March. While usual farming operations were taking place during the year 2013 a trial was carried out to artificially hatch eggs collected from some females (from the hatchery of San Vito) which were going to loose their deteriorating load of berried eggs. Still vital eggs were selected and collected and then moved to a "McDonald-type" incubation bottle. Here they completed their development and after less than 30 days first hatchlings have appeared. This significant result makes it feaseable to retrieve and regularly hatch eggs which cannot regularly develop and hatch onto the mother and it opens new scenarios for the supply of crayfish eggs for the hatchery. Eggs which could theoretically be collected directly from ovigerous females on natural sites. A similar trial is going on during Summer 2013 at the ETP Aquarium in Ariis di Rivignano (Udine). Neverthless, despite the above mentioned results a final judgement about this kind of procedures has to be assessed when final data on larvae survival will be available.


RESTOCKING

Restocking

Monitoring of stations during the first year of RARITY allowed for the elaboration (carried out by the Department of Biology of the University of Florence) of a detailed picture of the distribution and abundance of freshwater crayfish in Friuli Venezia Giulia. Contrary to expectations the native species has been found in only 25% of the sampled stations (208 total stations). According to other European regions this result confirms also in FVG the dramatic general trend showing a constant decrease of native crayfish species (which in FVG resist only in the piedmont areas characterized by lower anthropic impacts). By means of the research and the study work carried out by the Department of Life Science of the University of Trieste the sampled crayfish populations have been genetically characterized too. Genetic analyses allowed for a better understanding of the so called “Austropotamobius pallipes complex” represented in the Region FVG and consisting of 2 species (A. pallipes e A. italicus) and 4 sub-species (A. i. italicus, A. i. carinthiacus, A. i. meridionalis and A. i. carsicus). These analyses show the presence in FVG of the sub-species A. i. italicus and A. i. carsicus exclusively into the Torrente Rosandra and of A. i. meridionalis in the remaining 45 studied sites, while they didn't confirm the presence of Austropotamobius torrentium in the 3 stations where it has been historically reported. Furthermore, by the analysis of haplotypes crayfish populations have been clustered into ESU (Evolutionary Significant Units) which in turn allow for the management of crayfish stocks as separate units and for the conservation or even the increase of their specific genetic variability. These results are definitely crucial to the choice about where and how carry out proper soctk enhancing and restocking actions. Hatchery-reared individuals from farming plants come from breeders which belong to a particular ESU and must be released into natural environments hydrobiologically connected to populations from exactely the same ESU. Hatchery-reared crayfish juveniles have been farmed to the lenght of 2.0 cm which is the optimal size for their liberation in the nature. Due to their fragility during the first life times larvae have been collected and counted only close to their release into the natural sites. During the year 2012 hatchery-reared crayfish juveniles have been liberated in the two SICs “Risorgive dello Stella” (Udine) and “Risorgive del Vinchiaruzzo” (Pordenone). In the first site restocking took place in the water body called "Aghe Real" to re-settle the natural populations of native crayfish which had been deleted by a heavy dryness (on summer 2012). During the mentioned dryness episode 16 dying crayfish specimens were collected. They unfortunately died right after collection but they could be genetically analyzed. Later monitoring confirmed disapperance of the species from the site suggesting for it restocking with genetically fully compatible crayfish juveniles. After this experience ETP has now facilities and equipment for the artificial incubation of crayfish eggs (bottles of Zugg and McDonald) n case of eggs collected from dying or recently died mothers. In the second SIC 600 crayfish juveniles and 10 adults have been released in the attempt to rebuild rapidly a well-structured population capable to resist to the predatory pressure exercised by the marble trout living in the site. Preliminary monitorings had been carried out in this site with the aim to harvest some crayfish breeders fot the hatchery and showing the disappearance of local populations. These and other interventions have been realized. Crayfish breeders have been released into provenance sites sometimes joined by a number of juveniles to compensate for losses associated to the collection of specimens moved from nature to hatchery (this have been done for example in Rio Gorgons and Torrente Chiarzò). In the case of Roggia Redenta the site has been restocked by a couple of breeders (and their own offspring, born in captivity) harvested during an artificial dryness of the mantioned water body.


INFORMATION MATERIAL