**The title, authors, and abstract for this completion report are provided below.  For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**

Test of Pheromone Traps to Capture the Invasive Round Goby

Lynda D. Corkum¹ and Timothy B. Johnson²

1 Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 3P4

2 Ontario Ministry of Natural Resources, Lake Ontario Fisheries Station, R.R. #4, 41 Hatchery Lane, Picton, Ontario, Canada K0K 2T0

October 2007

ABSTRACT

We sought to develop and test odour traps that target the invasive fish, round goby (Neogobius melanostomus), resulting in a reduction in their abundance in critical habitats or limiting and possibly preventing their spread into new waterways. There is great value in reducing the reproductive success of round goby, the fastest spreading vertebrate ever reported in the Great Lakes. Our research builds on the hypothesis that the reproductive male round goby releases a sex attractant that lures gravid females to source odours. We use a variety of odours (males, females, male urine, food) to lure all stages and both sexes of the round goby to traps in flowing and still water. Our research program focused on 4 objectives: 1. Visual and chemical signaling in the round goby; 2. Evaluation of odour preferences of round goby in a large static arena (an above ground pool); 3 Comparison of the effectiveness of traps seeded with odours in capturing round gobies in Lake Erie and Lake Ontario; and, 4. the development of a slow-release tablet that would contain potent odours to lure round gobies to traps.

Our findings support the notion that reproductive male life-like models (made of silicon) with the presence of reproductive male urine (over a range of concentrations) lure gravid females to a nest in a laboratory flume (i.e. where flow is unidirectional). The visual cue (the reproductive male model) was more effective in luring gravid females than the non-reproductive model in clear water in the lab flume. Because male sex steroids are released in urine, we anticipate that chemical odours will be more effective in field situations where water is turbid than visual cues are in attracting gravid females.

Because odour traps will be deployed in different habitats (still and running water), we studied odour preference of round gobies in a large static arena (an above ground pool). Minnow traps separated by 90° and placed at each of four compass points around the pool with Lake Erie water were seeded with male, female, food (beef heart/yellow perch) or left empty (a control). Study results indicated that most round goby did not enter any of the traps. The traps seeded with black males (intended to be reproductive) were, after post-experiment dissection, found not to be spermiating. When data were re-analysed insuring that traps seeded with males were reproductive, data were still highly variable. Most fish did not enter traps.

We also determined the response of round gobies to food odours from lake whitefish Coregonus clupeaformis, dreissenids, and rainbow trout Oncorhynchus mykiss eggs in a lab flume and in traps deployed in Lake Erie at Rondeau Bay. No significant difference in the number of round gobies captured in traps were noted among treatments in the lab flume (χ²(0.05, 3) = 0.6, p > 0.05), indicating that fish exhibited no preference for any one food type. Results of planned comparison analyses of traps deployed in Lake Erie showed that there were significantly more round gobies caught in traps seeded with lake whitefish or dreissenids than traps seeded with fish eggs (F1, 64 = 4.132; p = 0.045). Of 106 individual fish caught, 96 were round gobies and most were non-reproductive males. Dreissenidae were the major prey type (36%) found in the digestive tracts of captured round goby. A complementary field study was conducted in the Bay of Quinte (eastern Lake Ontario) to compare the effectiveness of traps seeded with different odour types. Results showed that there were no significant differences in round gobies caught among treatments, owing to high variability in catch rate.

Exploration of the potential to develop a slow release tablet to administer odours in field settings was done in partnership with a contract pharmaceutical manufacturing company. A slow-release tablet has been formulated and subject to disintegration testing (basic breakdown properties), however, unanticipated high costs for a dissolution test needed to verify the slow release property have prevented a complete evaluation of the tablet performance.

Overall, our findings show that there is potential of using reproductive male urine in a tablet in a male model to lure females to traps. Without this scent, we have shown that traps seeded with food or adult gobies are not effective in luring conspecifics to traps.