Interlocked use of inland fish resources: a new management strategy under private property rights

Abstract  Interlocked use of multiple inland vendace, Coregonus albula (L.), stocks is a relatively new strategy to exploit asynchronous fluctuations in abundance of natural fish stocks between waterbodies. It combines vendace stocks from different lakes or parts of lakes into one interlocked stock to be managed across waterbody ownership boundaries. Management of interlocked stocks can be regarded as one form of portfolio management. Exploitation of interlocked stocks should reduce the interannual variation in yield, and thus ensuring fishers more constant income and the market more constant material flow. The strategy requires fishers to increase their mobility, to benefit from asynchronous fluctuations in abundance of vendace stocks between exploitable waters. A postal inquire addressed to Finnish commercial inland fishers examined whether existing property rights institutions' and fishers' harvesting policies were appropriate to establish interlocked use of multiple vendace stocks. Almost half of fishers had, to some extent, reaped benefit from a fishing strategy that included small-scale mobility, which is consistent with the proposed strategy. By harvesting three or four lakes and stocks, fishers increased their yield compared with exploiting one fishing ground and one vendace stock. Public ownership provided fishers access to stocks nearer their place of residence than other ownership types.     

Occurrence and pathogenicity of Yersinia ruckeri at fish farms in northern and central Finland

Abstract. Salmonid fish at fish farms in northern and central Finland and perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), and whitefish, Coregonus sp., from four lakes in central Finland were studied between 1985 and 1990 for the occurrence of Yersinia ruckeri. The bacteria were found in fish from both areas, but in most cases, only single diseased salmon, Salmo salar L., brown trout, S. trutta L., rainbow trout, Oncorhynchus mykiss (Walbaum), whitefish and perch were encountered and were always connected with stress conditions. One clinical outbreak occured in salmon fingerlings in northern Finland, and the fish were successfully treated with trimethoprim-sulpha. Monthly monitoring of lake fish revealed two symptomless carrier perch in two lakes. Outwith the main study a moribund perch with yersiniosis was found in a polluted lake, and for the first time in Finland, a rainbow trout was also found to have contracted yersiniosis in a small private pond. Sorbitol-positive and negative isolates have been found to occur in both moribund and carrier farmed fish, indicating that the sorbitol test is not essential when evaluating the pathogenicity of Y. ruckeri.     

Anatomy and dynamics of a supramolecular membrane protein cluster

Most plasmalemmal proteins organize in submicrometer-sized clusters whose architecture and dynamics are still enigmatic. With syntaxin 1 as an example, we applied a combination of far-field optical nanoscopy, biochemistry, fluorescence recovery after photobleaching (FRAP) analysis, and simulations to show that clustering can be explained by self-organization based on simple physical principles. On average, the syntaxin clusters exhibit a diameter of 50 to 60 nanometers and contain 75 densely crowded syntaxins that dynamically exchange with freely diffusing molecules. Self-association depends on weak homophilic protein-protein interactions. Simulations suggest that clustering immobilizes and conformationally constrains the molecules. Moreover, a balance between self-association and crowding-induced steric repulsions is sufficient to explain both the size and dynamics of syntaxin clusters and likely of many oligomerizing membrane proteins that form supramolecular structures.