Habitat Selection by Two Species of Cleaner Fishes That May be Beneficial in Removing Sea Lice From Cultured Salmon

Sea lice are detrimental ectoparasites that attach to Atlantic salmon causing physiological damage and costing farmers millions in inventory loss and treatments. Cleaner fishes have been introduced into sea cages to act as a biological control of sea lice which is likely a solution for Canadian salmon aquaculture industries. To improve cleaner fish foraging efficiency, this study seeks to determine the optimal habitat for cleaner fishes in Canadian aquaculture. I hypothesized that to be effective cleaner fishes, both the cunners and the lumpfish require habitats that provide them with shelter and places for rest because neither species live solely in the water column. My second hypothesis was that the cunners and the lumpfish require different habitats due to their different morphologies. Habitat comparisons were conducted with three habitats and a control in each individual fishes tank for a total of 8 cunners and 25 lumpfish. It was determined that only cunners required shelter, possibly due to the lumpfish’s ability to adhere to the glass tank walls for rest. Moreover, there was no significant difference in habitat preference between the two species. However, the lumpfish were less preferential between habitat and preferred three of the four habitats equally. It should be noted that the lumpfish and the cunners utilized the same habitats in separate ways to better fit their species-specific requirements; so future research on the co-existence of the two species could lead to increased foraging efficiency through two-species cleaner fish systems.

Small Mammals in Saltcedar (Tamarix ramosissima)–Invaded and Native Riparian Habitats of the Western Great Basin

Invasive saltcedar species have replaced native riparian trees on numerous river systems throughout the western United States, raising concerns about how this habitat conversion may affect wildlife. For periods ranging from 2 to 11 yr, I used live-trapping to monitor small mammal populations in paired saltcedar and native riparian woodlands at four sites in western Nevada and eastern California. Heteromyid rodents, such as Merriam's and Ord's kangaroo rats, were more likely to occur in saltcedar habitats, but other rodent species, particularly the montane vole and western harvest mouse, occurred more often in native habitats, and this balanced species richness in habitat comparisons. The most common species at all sites, the deer mouse, did not show any consistent differences in abundance or in mean body mass between the two habitat types. However, the ratio of captured male to female deer mice was higher in saltcedar than native habitats at two sites. Deer mice as well as Ord's kangaroo rats also had higher rates of being recaptured following initial capture in native habitats, which may have been due to fewer transient individuals occurring in these habitats. By contrast, Merriam's kangaroo rats may have been more transient in native habitats because they were more likely to be recaptured in saltcedar. Individuals of two species, pinyon mouse and white-tailed antelope ground squirrel, had greater mean body mass in native habitats than they did in saltcedar, implying that they may have maintained superior condition in native habitats.

An account of Southern Australian Species of Mesophyllum (Corallinaceae, Rhodophyta)

Mesophyllum (Corallinaceae, Rhodophyta) is represented in southern Australia by at least four species. M. engelhartii and M. incisum have been reported from the region previously, M. macroblastum is newly recorded, and M. printzianum is newly described. Detailed accounts are provided for each species along with information on etymology, nomenclature and synonymy, collections examined, infraspecific taxonomy, and distribution, seasonality and habitat. Comparisons of southern Australian species with the type species of Mesophyllum, M. lichenoides, also are included. Of the nine additional entities that have been recorded from southern Australia under the generic name Mesophyllum, three (M. fumigatum, M. lemniscatum, M. versicolor) are considered heterotypic synonyms of M. engelhartii, three are referable to other genera of Corallinaceae (M. gabrielii to Lithothamnion; M. patena to Synarthrophyton; M. rupestre to Hydrolithon), two (M. lichenoides, M. neglectum) are based on misidentifications or questionable records, and one (M. squamuliforme) is treated as a species of uncertain status. Southern Australian specimens previously referred to Clathromorphum have been found to belong to Mesophyllum. As a prelude to the taxonomic accounts, a short historical introduction is provided along with a brief consideration of general morphological and anatomical features of Mesophyllum and a detailed analysis of characters that have been or could be used to delimit species within the genus. None of the at least 26 characters used by previous authors or the 34 quantitative characters examined during the present study were found to be of diagnostic value. By contrast, qualitative characters associated with tetrasporangial / bisporangial conceptacle roof morphology and anatomy have provided a reliable basis for delimiting the four southern Australian species from one another and from the type species of the genus, M. lichenoides. Concluding remarks, acknowledgments and references follow the taxonomic accounts.

Cycle vital et croissance de Bithynia tentaculata L. (Mollusca, Gastropoda, Prosobranchia) du Lac St-Louis près de Montréal

A total of 13468 specimens of Bithynia tentaculata were collected at four sampling sites on Lake St-Louis from May 1968 to July 1969. To obtain a representative sample of the populations, various collecting methods were used. The life history and the growth at each station were compared and correlated with the physical and chemical features of the habitat. Comparisons with Lilly's (1953) observations in Britain are also included.