N41 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.S. Mitchell and C.F. Purchase Rapid Colonization of a Species at Risk: A New Eastern Range Limit for Fundulus diaphanus (Banded Killifish), in Newfoundland Jeremy S. Mitchell1,* and Craig F. Purchase2 Abstract - We documented a new population of Fundulus diaphanus (Banded Killifish) in Burton’s Pond, within the City of St. John’s, Newfoundland. To our knowledge, the Burton’s Pond population is at the eastern limit of Banded Killifish’s known occurrence in North America, and it has only existed since 1999. It represents a significant change in the species’ continental distribution, and a very significant addition to its occurrence in Newfoundland, where Banded Killifish are listed under provincial and federal species-at-risk legislation. Fundulus diaphanus Lesueur (Banded Killifish) are abundant throughout much of eastern North America but have an extremely limited distribution on the island of Newfoundland. Prior to this study, 10 Banded Killifish populations had been documented on the island: 9 in the south and southwest of the island, and the tenth in the north-central region (Fig. 1; Chippett 2003, Fisheries and Ocean Canada 2011, Gibson et al. 1984, MAMKA 2006, Scott and Crossman 1965). Fisheries and Oceans Canada (2011) summarizes evidence for a limited number of possible, additional populations or subpopulations. The populations in the south and southwest are assumed to be naturally occurring. Chippett (2003) notes that the north-central population (Indian Bay watershed) may be the result of an introduction by anglers using the species as bait. Adaptive differences and the level of reproductive isolation between Newfoundland and mainland populations are unknown. Chippett (2004) found no differences between Newfoundland and mainland populations in a limited study with allozymes. Newfoundland Banded Killifish can be locally abundant where they occur. However, the area occupied is limited in each case, and river gradients and physical barriers limit opportunities for range expansion, migration, and recolonization (in the event of local extirpation). These factors have led to the listing of Newfoundland Banded Killifish as a species of special concern under the Canadian Species at Risk Act, and as vulnerable under the Newfoundland and Labrador Endangered Species Act (COSEWIC 2003, Fisheries and Oceans Canada 2011). Here, we document a previously unreported population of Banded Killifish in Burton’s Pond, a small lake (~8100 m2 in area) located on the campus of Memorial University of Newfoundland in St. John’s (47.574°N, 52.728°W; Fig. 1). Banded Killifish were first detected in Burton’s Pond in 2009 by one of the authors (J.S. Mitchell, unpubl. data). Informal inquiries suggest that the population is the result of a single introduction of 6–9 fish in 1999, originating from the Indian Bay population. Burton’s Pond has no surface connection to adjacent water bodies, but is connected to Rennie’s River through the city’s storm-sewer system. In 2010, 4 Banded Killifish were collected by electrofishing from Rennie’s River (P. Westley, University of Washington, Seattle, WA, unpubl. data). To date, Banded Killifish have not been detected, despite targeted effort, in either Long Pond or Quidi Vidi Lake, upstream and downstream from Rennie’s River. 1Fish Evolutionary Ecology Research Group, Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada. 2Fish Evolutionary Ecology Research Group, Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B 3X9, Canada. *Corresponding author - jsmitchell@mun.ca. Manuscript Editor: John Waldman Notes of the Northeastern Naturalist, Issue 21/3, 2014 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N42 J.S. Mitchell and C.F. Purchase To better characterize the Burton’s Pond Banded Killifish population, we used minnow traps to capture, measure, and, later in the sampling period, sex adult killifish. We set traps intermittently 8 May–5 July 2012. In total, we captured 568 unique (non-recapture) adult killifish with a range of 44–92 mm standard length (SL). Two distinct length classes were present, with modes at approximately 50 and 68 mm SL (Fig. 2). We interpreted these as year classes (likely age 2 and 3). The shorter length class was captured less frequently than the longer. Large numbers of juveniles (likely age 1) were observed and could be caught by netting, but we caught no juvenile killifish in minnow traps. Adult males were caught less frequently than adult females. Females with ripe eggs (female size range = 50–84 mm SL) were first collected on 23 May at a water temperature of 17 °C, and were present among both apparent size cohorts into early July. We captured assumed young-of-year (but possibility age 1+) with a fine-mesh aquarium dipnet on 21 September 2012; they had a mean length of 25.6 ± 4.49 mm SL, (n = 119). All Banded Killifish appeared healthy with no obvious signs of parasites; we did not investigate what they are eating in Burton’s Pond. In 2013, we placed artificial spawning mops in the pond, and Figure 1. Map of insular Newfoundland, with the locations of previously known Banded Killifish populations, and the Burton’s Pond population in the city of St. John’s (cf. Fisheries and Oceans Canada 2011). N43 2014 Northeastern Naturalist Notes Vol. 21, No. 3 J.S. Mitchell and C.F. Purchase fertilized eggs were first deposited on them on 10 June. The number of fish captured, the presence of multiple size classes, the occurrence of fertilized eggs, and our observations of juvenile fish in late summer all confirm that Banded Killifish are reproducing and recruiting successfully in Burton’s Pond. In the summers of 2012 and 2013, a family of Sterna hirundo L. (Common Tern) were raised on a small island in Burton’s Pond. The only other regular species of fish in Burton’s Pond were Gasterosteus aculeatus L. (Three-spined Stickleback). The birds fed heavily on the Banded Killifish, and thus the rapid colonization appears to have altered the local ecosystem. Terns were observed eating killifish on a wharf on nearby Long Pond (~500 m away), but we are uncertain whether they were brought there by the birds, or captured there (G. Herzberg, Department of Biochemistry, Memorial University of Newfoundland, St. John’s, NL, Canada, pers. comm.). The Burton’s Pond population of Banded Killifish is of biogeographic interest because it is at the easternmost limit of the species’ range in Newfoundland and in North America. It is approximately 200 linear km from the nearest known population. The new population is of added significance because Newfoundland Banded Killifish populations are listed under both Newfoundland provincial and Canadian federal endangered species legislation, with management plans emphasizing habitat protection (COSEWIC 2003, Fisheries and Ocean Canada 2011). The speed with which a single limited introduction has grown to become a substantial population suggests that, should one or more of the naturally occurring populations fail, restocking may be feasible. Because the Burton’s Pond population appears to be the result of a human introduction, it is not clear that it should be accorded the same protection as other populations on the island. Figure 2. Length-frequency distribution of adult Banded Killifish in Burton’s Pond. In order to limit variation due to growth, data are presented for the subset of fish captured by minnow trap over a 2-week period 14–28 June 2012. 2014 Northeastern Naturalist Notes Vol. 21, No. 3 N44 J.S. Mitchell and C.F. Purchase Acknowledgments. We thank Mark Abrahams and Peter Westley for useful discussions, Justin Strong for catching most of the fish, and John Waldman and two anonymous reviewers for comments on the manuscript. This research was funded through an NSERC Discovery grant to Craig Purchase and an NSERC undergraduate student research award to Justin Strong. Jeremy Mitchell was funded through a Memorial University postdoctoral research fellowship to Mark Abrahams’ laboratory. Banded Killifish were captured under experimental licence NL–917–12 from Fisheries and Oceans Canada and Memorial University Animal Care Protocol 12-04-CP. Literature Cited Chippett, J.D. 2003. Update Committee on the Status of Endangered Wildlife in Canada (COSEWIC) status report on the Banded Killifish, Fundulus diaphanus, Newfoundland population in Canada. Pp. 1–21, In COSEWIC assessment and update status report on the Banded Killifish, Fundulus diaphanous in Canada. Ottawa, ON, Canada. Chippett, J.D. 2004. An examination of the distribution, habitat, genetic, and physical characteristics of Fundulus diaphanus, the Banded Killifish, in Newfoundland. M.Sc. Thesis. Memorial University of Newfoundland, St. John’s, NL, Canada. x + 154 pp. COSEWIC. 2003. COSEWIC assessment and update status report on the Banded Killifish, Fundulus diaphanus, Newfoundland population in Canada. Ottawa, ON, Canada. 22 pp. Fisheries and Oceans Canada. 2011. Management plan for the Banded Killifish (Fundulus diaphanus), Newfoundland Population, in Canada [Final]. Species at Risk Act Management Plan Series. Fisheries and Oceans Canada, Ottawa, ON, Canada. v + 23 pp. Gibson, R.J., J.-P. Thonney, and K. Hillier. 1984. An easterly extension in the known range for Fundulus diaphanus in Newfoundland. Le Naturaliste Canadien 111:213–214. Houston, J. 1990. Status of the Banded Killifish, Fundulus diaphanus, in Canada. Canadian Field- Naturalist 104:45–52. Mi’kmaq Alsumk Mowimsikik Koqoey Association (MAMKA). 2006. Banded Killifish: Monitoring the by-catch in the eel fishery. Corner Brook, NL, Canada. 18pp. Scott, W.B., and E.J. Crossman. 1964. Fishes Occurring in the Fresh Waters of Insular Newfoundland. Queen’s Printer, Ottawa, ON, Canada. 124 pp.