Banded Killifish (Fundulus diaphanus) and Mummichog (Fundulus heteroclitus) distributions in insular Newfoundland waters: implications for a Species at Risk

Newfoundland’s Banded Killifish (Fundulus diaphanus) population is listed as a species of Special Concern under Canada’s Species at Risk Act and Vulnerable under Newfoundland and Labrador’s Endangered Species Act. Mummichog (Fundulus heteroclitus) is a similar looking fish species and is currently under review by Newfoundland and Labrador’s Species Status Advisory Committee. Both species have limited known distributions in Newfoundland waters that overlap. They may occur sympatrically in estuaries and occasionally hybridize; thus, field identifications can be challenging. We found that dorsal fin position and caudal fin depth were the most useful morphological characters for distinguishing Banded Killifish and Mummichog in the field. We used local ecological knowledge, literature review, museum records, and field surveys to update the known distribution ranges and found both species in more locations than previously documented in Newfoundland. Thus, we extend their known ranges. Our results will be critical in future status assessments of these species in Newfoundland.

Comparative Efficacy of Pimephales promelas, Fundulus diaphanus, and Gambusia affinis and Influence of Prey Density for Biological Control of Culex pipiens molestus Larvae

ABSTRACT Larval survival times and density-dependent feeding behavior were evaluated with the use of 2 species of fish native to the northeastern USA (Pimephales promelas and Fundulus diaphanus), and the potentially invasive Gambusia affinis. Each species was provided 10, 20, 30, 45, and 60 4th-stage larvae of Culex pipiens molestus/fish in the laboratory and digital images were recorded to quantify the number of surviving larvae at various intervals. Daily feeding rates were greatest at the highest larval density. These were 49.69 ± 4.07 larvae for P. promelas, 60 larvae for F. diaphanus, and 36.44 ± 6.6 larvae for G. affinis. Survival analysis was used to compare efficacy of each fish species over time. All fish species consumed larvae at similar rates at lower densities, but significant differences occurred at densities of 30–60 larvae/fish. Survival times of larvae at the highest density were 44 ± 7.9 h for P. promelas, 15 ± 3.4 h for F. diaphanus, and 70.6 ±13 h for G. affinis. In order to evaluate feeding rate as a function of prey density, we compared consumption rates 1.5 h after feeding with the use of a 4-parameter logistic model. Fundulus diaphanus and G. affinis feeding aligned with the 4-parameter model, indicating that initial feeding rates for these species increased with prey density to an upper limit (satiation). Pimephales promelas feeding within 1.5 h did not align with this model, suggesting that early feeding rates for this species are not heavily influenced by prey density.

Régime alimentaire des dorés jaunes et noirs de la région de Québec : une nouvelle proie, le gobie à taches noires

Des données recueillies entre 1999 et 2010 sur les contenus stomacaux de dorés jaunes (Sander vitreus) et de dorés noirs (S. canadensis), capturés à la ligne dans le fleuve Saint-Laurent et aux embouchures de quelques tributaires de la région de Québec, ont permis de mettre en évidence le fait que le gobie à taches noires s’y était bien implanté depuis 2004. Une baisse de la présence de certains poissons indigènes dans les contenus stomacaux des 2 espèces de doré a été observée à partir de cette année charnière, après laquelle le gobie à taches noires a été commun en tant que proie chez le doré jaune. Cette même proie représentait plus du quart des espèces identifiées dans les estomacs de dorés noirs durant toute la période de l’étude. Les autres proies principales des 2 espèces de dorés étaient l’épinoche à 3 épines (Gasterosteusaculeatus), le fondule barré (Fundulus diaphanus) et le dard noir (Etheostomanigrum). Les classes de longueur les plus fréquentes chez les dorés jaunes échantillonnés étaient celles comprises entre 276 et 395 mm.

Influence of historical events and contemporary estuarine circulation on the genetic structure of the banded killifish (Fundulus diaphanus) in the St. Lawrence River (Quebec, Canada)

Eight microsatellite markers were used to examine the historical and contemporary factors influencing the distribution of genetic variation within and among populations of Fundulus diaphanus (Lesueur, 1817) in the St. Lawrence River. Our results show that the contemporary hydrodynamics of the river affect levels of diversity and differentiation in this species. Genetic diversity increased towards downstream sites and levelled off at the upstream end of the tidal section, in the vicinity of Lake St-Pierre outlet. Likewise, differentiation and isolation-by-distance were most pronounced in the upstream, strictly fluvial section of the river. Surprisingly, however, we did not detect any significant intershore differentiation in this riparian fish species. Historical influence was also clearly detected and transcended the contemporary pattern, as revealed by an extremely strong isolation-by-distance pattern along the entire river stretch. This pattern likely results from the historical, postglacial secondary contact between two glacial races, as indicated by the clinal variation of constrasting allele size frequency distributions along the river and the significantly greater values of differentiation indices considering mutational information.