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Analysis of long-term catches from the deep peri-alpine Lake Geneva, showed a shift in the stock-recruitment relationship of Coregonus lavaretus (L.), a target species of commercial fishing. This change was mainly related to large-scale meteorological factors. Higher spring water temperatures may have improved larval survival and hence recruitment of whitefish via: (1) a better match between the hatching date of whitefish larvae and development of their zooplankton prey; and (2) the positive temperature effect on larval growth. In Lake Geneva, changes in regulatory mechanisms coupled with stocking and improved water-quality have led to an explosion in the C. lavaretus population in recent years. These results highlight the relevance of long-term changes in the stock-recruitment relationship for management of aquatic ecosystems that are sensitive to climate forcing. [ABSTRACT FROM AUTHOR]

Rationale: Sequential analysis of otolith oxygen isotope (δ(18) O(oto) ) values was performed by classical mechanical microdrilling and dual inlet mass spectrometry to infer the timing of growth checks in pike (Esox lucius) scales from Lake Annecy (France). It indicated that the first check on scales occurs before the first winter of life of the fish., Methods: Eleven fish caught in February and June 2008 were studied. Intra-individual isotopic profiles exhibit cyclic variations that are consistent with that of modeled δ(18) O(oto) values using variations in epilimnion temperature and otolith-specific isotope fractionation equations. The positions of growth checks on scales were compared with the periodic variations of δ(18) O(oto) values on otolith radii using an allometric relationship., Results: All individuals presented at least one check deposited before the first winter. Deposition of some checks might be linked to a shift in fish diet or habitat or to catch-and-release induced stress., Conclusions: Although coupling between sequential analysis of δ(18) O(oto) values and observation of scale growth features has been shown to be useful, there are limitations in the methodology, especially for the growth-attenuated region of otoliths associated with older ages., (Copyright © 2012 John Wiley & Sons, Ltd.)

The genetic structure of the most abundant species in the genus Eubothrium, E. crassum and E. salvelini, was studied by allozyme analysis in order to provide a consistent diagnosis for these morphologically similar species, as well as to assess their genetic relatedness. The proportion of fixed allelic differences (56.3%, 9 of 16 loci) between the species falls within the range accepted for valid species. A strict host specificity of E. crassum and E. salvelini for their typical host (lake trout, Arctic charr, respectively) was found in the French localities examined (Lake Annecy, Lake Bourget). For E. salvelini, polymorphism with the established allelic profile was found in the acid phosphatase (ACP) system. No significant deviation from the Hardy-Weinberg equilibrium expectations for ACP were found in either of the E. salvelini populations, which suggests predominantly cross-fertilization of these hermaphrodites. Analysis of the standardized variance in allelic frequencies demonstrated almost no among population differentiation (estimator theta of Fst = -0.03) between E. salvelini populations., (Copyright 2004 Springer-Verlag)

Seasonal occurrence in terms of prevalence, intensity of infection, abundance and density of the tapeworm Proteocephalus longicollis (Zeder, 1800) and its transmission between its intermediate host (Cyclops abyssorum prealpinus) and definitive host (common whitefish, Coregonus lavaretus) in Lake Annecy, an oligotrophic lake in the western part of the Alps, France, were studied in the period of 1998-2000. A copepod Cyclops abyssorum prealpinus (Kiefer, 1939), the dominant species among planktonic crustaceans in the lake, served as the only intermediate host for this parasite. Infection with plerocercoids was higher in adult copepods (predominantly females) than in copepodite stages IV and V. The prevalence rate of 25% found in C. abyssorum prealpinus females in June 1998 represents a unique infection rate of intermediate hosts with fish tapeworms in natural conditions. The final host, the common whitefish Coregonus lavaretus (L.), was heavily infected with P. longicollis throughout the year (prevalence 90%; mean abundance 40.3; maximum intensity of infection more than 500 tapeworms per fish); immature tapeworms predominated in all samples (P<0.01). Transmission of tapeworm larvae from copepods to the common whitefish took place most intensively in summer and autumn, and depended on seasonal changes in the density of the C. abyssorum prealpinus population, infection of this copepod with plerocercoids and their density in the lake. In addition, transmission efficiency also seems to be determined by the longevity of tapeworm larvae in the intermediate host, timing of predation of the fish host and rapid development of the parasite within this host during the summer period. Overall transmission potential of P. longicollis was low, with only about 9% of juvenile specimens reaching maturity in common whitefish.