Fish farms in Northern Israel (NI) suffer from parasitic trematodes with a complex life cycle which attack fish, causing slow growth rates and higher mortality. The trematodes transmit through freshwater snails, including: local species (Melanopsidae and Theodexus) found in natural springs; invasive species (Thiara scabra; Tarebia granifera; Pseudosuccinea columella) and overabundant local species (Melanoides Tuberculata), found in huge numbers in the fish farm vicinity.
The variety of regional water transport systems is suspected to impact the dispersal abilities of the snails, ranging from undisturbed flow to man-made trenches and pumps. Within these combinations, the complex system of parasite-carrying snail populations can be classified according to ecological metapopulation models.
Fish farms integrate pesticides and prawn biocontrol against snails, being easier targets than trematodes. The prawns, Macrobracium rosenbergii, voracious snail predators, have proved to be successful, yet limited to the single fishpond.
We aim to utilize the local potential of the prawn biocontrol on a regional scale, which requires a deeper understanding of the snail metapopulation structure and trematode hubs. Thus, we surveyed six representative freshwater tracks in NI to find potentially influential spots for prawn biocontrol against parasite-carrying snails in this spatially explicit system.
KM
The survey focused on the snail populations from the sources to the fishponds (Fig.1), while also testing middle points in which the water system changed (i.e., from undisturbed flow to concrete trench). We screened snails from each sample point for parasitic trematodes, using general trematode 18s primers, to find trends in snail infection rates along the tracks. We will discuss the change in snail population structure, and trematode presence along the representative water tracks, and the ongoing efforts in fitting the best suiting metapopulation model to each of the tracks.
This survey will be an important base for further regional biocontrol efforts, and could possibly serve as a template for other areas attempting to use biocontrol against the same parasitic cycle or invasive snails.