Dariusz Nowak School of Natural Sciences National University of Ireland Galway

Dariusz Nowak School of Natural Sciences National University of Ireland Galway

Aims Development of new, efficient and cost effective baited trap protocols. Specific (target) benthic invertebrate sampling. Focus on invertebrate taxa which may not be numerically abundant but are identified as being important for monitoring subtle anthropogenic change in lake ecosystems.

Study Area Lough Mask is the 6 th largest lake in Ireland located in the west. It is part of the Corrib Catchment which has a total area of ~3,km 2. Total area of 82.75km 2. Max. depth ~58m Axial length ~16km. Oligotrophic/Mesotrophic. 1 2 3 3 littoral areas were selected for field experiments. GIS Licence No. NUIG283 GIS Data: OSI

Turbellaria: Tricladida. Selected species: Polycelis nigra, Dugesia polychroa and Dendrocoelum lacteum. Free-living, freshwater flatworms that live on bottom substrates such as mud, stones, macrophytes and submerged objects. Dendrocoelum spp. These 3 taxa were selected because of their relative abundance in the study area and their slow, easily observed movement. 25 Species Abundance Dugesia spp. 2 N / m 2 15 1 5 D. lacteum D. polychroa P. nigra Polycelis spp.

Laboratory Experiments Choice-chambers were used to assess individual species responses to alternative bait types (2 bait types, 3 flatworms per experiment). 6 bait types or a control (water only) as potential attractants (or repellents) were evaluated. Baits were homogenised, organic material (A F) stored at -2 C prior to the experiment to ensure standardised test protocols. Responses of each species were tested (3 repeats per bait type), noted and observed using an infra-red video camera. Experiments were conducted at night, in darkness in an isolated laboratory environment. Bait types: A. - Lumbricus tissue, B. - fresh Rutilus tissue, C. - decomposing Rutilus tissue, D. - chironomid/oligochaete tissue, E. - fish viscera, F. - Potomogeton crispus, G. - control (empty).

Apparatus An apparatus was designed and constructed in order to determine preferred bait types for each group of triclad. The apparatus was made up of 1 channels with fresh water collected from L. Mask flowing through the channels. Each channel had a choice-chamber (N=1) in the middle and a bait chamber (N=2) at each end. The apparatus was calibrated, so that the speed of water flowing from a tap in each bait chamber and along each channel was the same. Bait chamber Choice chamber Flow Tap Outlet

Laboratory Experiments Results 1 5 D. lacteum Most attractive bait was identified for each group. -5 A B C D E F G D. lacteum: decomposing Rutilus tissue, -1 Dugesia spp. Dugesia spp. : chironomid/oligochaete tissue, 1 5 Polycelis spp. : Lumbricus tissue. -5 A B C D E F G Bait types: A. - Lumbricus tissue, B. - fresh Rutilus tissue, C. - decomposing Rutilus tissue, D. - chironomid/oligochaete tissue, E. - fish viscera, F. - Potomogeton crispus, G. - control (empty). -1 1 5-5 -1 Polycelis spp. A B C D E F G

Field Experiments Feb. / Mar. / Apr. Night #1 species 1m 2 G methods nights 3 1m 2 Night #2 G baits months zones Night #3 1m 2 G Each method was compared to each other with regard to quality and quantity of collected samples.

Bait Trap Cheap and less labour intensive trapping method. Can be targeted to a particular group of animals. Easy to deploy in any aquatic habitat. Large area sampled (semi-quantitatively). Bait holder Funnelled entrance

Standard Sampling Methods 1. 1m 2 quadrat, hand collection. 2. Van-Veen Grab (~.2m 2 ). 1 m 2 grid http://cramp.wcc.hawaii.edu/lt_montoring_files/lt_benthi c_monitoring.htm Van-Veen grab http://www.duncanandassociates.co.uk/equip.htm

Results Qualitative Abundant species were detected by all 3 sampling methods. Less abundant species e.g. D. lacteum were more difficult to detect by standard methods. 1% Percentage D. lacteum detections 8% 6% 4% 2% % Van-Veen 1m2 quadrat Bait trap

Results Quantitative Results of trap tests (N=81) in L. Mask Bait type Night D. lacteum Dugesia ssp Polycelis ssp. #1 18 1 23 32 16 37 26 37 37 Feb #2 22 24 15 38 33 21 31 32 32 #3 19 2 18 36 19 28 4 31 29 #1 19 13 17 36 4 32 27 26 36 C Mar #2 15 1 18 32 34 37 36 36 39 #3 1 9 16 36 37 21 38 35 35 #1 1 7 9 21 18 15 36 32 35 Apr #2 9 6 12 47 32 41 36 25 3 #3 15 9 1 39 33 34 35 24 34 #1 2 4 41 39 37 2 23 27 Feb #2 3 57 4 4 49 45 49 #3 5 5 3 48 32 45 34 29 21 #1 4 4 3 41 45 36 48 35 39 D Mar #2 1 2 4 36 5 47 34 34 44 #3 1 3 32 21 39 21 32 44 #1 4 3 3 37 29 31 2 24 Apr #2 3 3 22 28 31 46 49 5 #3 1 2 25 2 33 46 5 48 #1 12 11 11 11 31 39 42 39 49 Feb #2 3 1 27 6 23 53 43 5 #3 3 8 9 8 38 39 37 42 A #1 6 1 3 15 31 26 52 47 49 Mar #2 9 9 11 6 1 36 41 45 41 #3 7 1 15 34 15 33 35 38 31 #1 1 1 12 32 12 25 4 32 47 Apr #2 12 8 11 26 16 13 27 39 32 #3 2 2 6 34 25 13 46 34 44 3 monthly mean trap tests results Bait type D. lacteum Dugesia ssp Polycelis ssp. C 14.19 31.3 32.96 D 2.22 36.33 36.74 A 7.48 22. 41.26

Results Quantitative - Lough Mask bait preferences Lake trapping generally confirmed laboratory experiments results. Most effective baits for species were those indicated by laboratory preferences. Highest trap selectivity observed for the least abundant species (D. lacteum). 45 4 35 3 25 2 15 1 5 D. lacteum C D A 45 4 35 3 25 2 15 1 5 Dugesia spp. C D A 45 4 35 3 25 2 15 1 5 Polycelis spp. C D A

Optimal trapping results (only preferred baits for each species) compared with results for standard methods 3 25 Mean Mean±SD Mean±1.96*SD D. lacteum 6 5 Dugesia spp. 6 5 Polycelis spp. 2 4 4 15 3 3 1 2 2 5 1 1 Van Veen Quadrat Bait Trap Van Veen Quadrat Bait Trap Van Veen Quadrat Bait Trap Means +- SD and ranges of numbers per sampling unit for 3 species and 3 methods. (N.B. Different vertical scales).

Conclusions Bait trapping is a non-intrusive and non-destructive sampling method. Bait traps can be set in a wide range of freshwater habitats. Bait traps can be more cost effective and less labour intensive than other methods. Information on responses of target species to alternative baits is required for optimal trapping Bait trapping can be particularly effective for obtaining samples of rare taxa.

References Ball, I. R. and T. B. Reynoldson 1981. British Planarians. Cambridge Univ. Press, London. Maitland, P.S., 1977. A Coded Checklist of Animals occurring in Fresh Water in the British Isles. Institute of Terrestrial Ecology. Reynoldson, T.B. 1967. A key to the British species of freshwater triclads. Sci. Publ. Freshw. Biol. Ass., 23, 1-28. Western River Basin District Eel Management Plan, December 28. The Department of Communications, Energy and Natural Resources.