Morphological variation in diadromous and landlocked populations of the spotted galaxias,Galaxias truttaceus,in Tasmania,south-eastern Australia

Synopsis A comparison of a suite of morphometric measurements and meristic counts of individuals of two landlocked lacustrine and two diadromous riverine populations of Galaxias truttaceus was carried out utilising both univariate and canonical variate analyses. Lacustrine fish had fewer dorsal and anal fin rays than did riverine fish. Differences were not as clear for gill rakers and vertebrae. Comparisons of serial counts were made with two derived lacustrine species, G. auratus and G. tanycephalus, also from Tasmania. Lacustrine G. truttaceus varied in the same direction as the derived species, relative to riverine G. truttaceus. From an analysis of 12 body measurements, the first canonical variate clearly separated lacustrine fish from riverine fish largely based on measurements associated with fins (pre-anal fin length, length of anal base, pre-dorsal fin length, maximum length of dorsal fin and inter-orbital width). An overall value for the correct classification of fish into groups based on locality was 84%. The percentage of fish classified into the wrong habitat (lake or stream) was much less than the percentage classified between localities within habitats. Overall morphological variation was greater between than within habitats. It is suggested that the differences in water movement and food type may in part account for the differences shown and that selective pressures peculiar to the lacustrine environment may be causing the lake populations to diverge from the riverine populations.     

Population structure and biology of alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) in the Saint John River,New Brunswick

Synopsis Examination of more than 2,000 alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis) from various areas in the Saint John River, N.B., showed differences in their morphometric and meristic characters. They differed also in length and age, compositions, spawning time, length and age at maturity, back-calculated lengths, and growth parameters. Within each species, between-area comparisons showed significant differences in some of their meristic characteristics.To test a homing hypothesis for alewives, a multivariate analysis was performed on eight meristic characters. Two discriminant function programs, discriminant analysis for two groups and a multiple group stepwise discriminant analyses were used. Values of the generalized Mahalanobis D² and percent overlap in frequency distributions of meristic characters suggest that considerable straying of fish, especially between adjacent areas occurs during upstream spawning migration.This article is one of several papers presented at the Second European Ichthyological Congress, Paris, 8–15 September 1976, to be published in Environmental Biology of Fishes.     

A further occurrence of Atherina boyeri Risso 1810 in North-Eastern Atlantic waters

Synopsis A further occurrence of Atherina boyeri in British waters is recorded. This species has a distribution which can be broadly defined as Mediterranean but has been occasionally recorded in waters which are beyond the northerly limits of its normal range. These records have usually been associated with localised thermal pollution but, at Oldbury-upon-Severn, England, this is probably not so. Morphometric and meristic data are presented which show clearly that this is a genuine record of A. boyeri. The existence of this species in waters with minimal, if any, thermal enrichment raises interesting questions regarding its distribution.This example and the other abnormal records of A. boyeri are, therefore, considered in relation to a number of environmental parameters. The parameters discussed, namely increased water temperature, decreased salinity and lagoon conditions have all been implicated in previous records.The conclusion tentatively reached is that A. boyeri is capable of surviving under a cooler temperature régime than that with which it is normally associated. Normally its range is restricted by inter-specific competition. In conditions of calmer water, however, in which there is also reduced salinity it is able to compete and maintain itself successfully.     

Phenotypic plasticity of a transplanted population of dwarf cisco,Coregonus artedii

Synopsis A population of dwarf cisco in Minnesota was studied in native and transplant environments. Life history characters were recorded and the stability of meristics and morphometrics of the population over a two year period in three different environments was assessed with univariate and multivariate statistics. Transplanted cisco lived longer and grew larger than they did in their native lake, yet retained distinctive pigmentation patterns and an unusually early spawning season. Meristic characters of dwarf fish remained within ranges reported forCoregonus artedii during the lifetimes of individuals in their new environments, but morphometric measures underwent significant size- and shape-related changes. Incubation and rearing studies show egg incubation time and behavior of larvae were identical of those of non-dwarf cisco. Comparisons with non-dwarf cisco populations illustrate the ecophenotypic plasticity of adult fish of this population of North American cisco. Present address: Fish Division, Museum of Zoology, University of Michigan, Ann Arbor, MI 48109, U.S.A.     

Hybridization of Cyprinus carpio and Carassius auratus,the first two exotic species in the lower Laurentian Great Lakes

Synopsis A preliminary comparison of Cyprinus carpio × Carassius auratus hybrids with the parent species is made by means of hybrid indices for 29 morphometric and 19 meristic characters. Of these 48 characters 29 were intermediate, seven were identical with one of the parents and 12 were extreme. Marked osteological differences in the crania of the parent species were noted as possible diagnostic characters for the identification of hybrids.Note