To sea or not to sea: Brook trout life history strategies and tactics during the last years

Transcription

1 To sea or not to sea: Brook trout life history strategies and tactics during the last years Allen Curry Canadian Rivers Institute New Brunswick Cooperative Fish and Wildlife Research Unit Biology Department Faculty of Forestry and Environmental Management and a cast of many

2 Basic requirements: -cold water (15 o C) -well-oxygenated -freshwater (reproduction) Eastern Brook Trout (that is really a charr) Salvelinus fontinalis Family Salmonidae Coregoninae Coregonus - whitefishes and ciscos Prosopium - round whitefishes Thymallinae Thymallus - graylings Salmoninae Oncorhynchus - Pacific salmon and trout Salmo - Atlantic salmon and brown trout Salvelinus - charrs (Arctic, Lake, and Brook)

3 Life History freshwater fish spawning (reproduction) adults (a rather large example) juveniles embryos

4 Life History (con( con t) BUT, some like to go to sea where they can grow big anadromous or sea-run populations

5 variability of life history tactics (Power 1980) where sea-run and considered anadromous, commonly sympatric with river residents (Power 1980) but,, these original models were based on single or few points in time and space captures

6 Our objectives: 1. Increase spatial and temporal information about life history tactics (to sea or not to sea). 2. Test hypotheses regarding origins of sympatric tactics of anadromy and residency (why go to sea?). Our working, alternative hypotheses: a) secondary contact of resident and anadromous genotypes: : predict strong genotypic differences b) anadromous form evolving from residents: - straying residents - low genotypic differences c) resident forms evolving from anadromous forms: - re-colonization and access to headwaters from sea - intermediate genotypic differences

7 Methods 1. Acoustic and radio tracking 2. Fish counting fences 3. Microsatellite DNA 4. Physiological parameters of anadromy, e.g., plasma

8 Study Sites: Laval River Petite Cascapedia River Nepisiguit River Fredericton Kennebecasis River

9 BAIE LAVAL (St. Lawrence River Laval River, Quebec sympatric populations <50 km intermediate gradient cold/cool freshwaters warm shallow estuary cold marine Laval River Lac a Jacques 4 km Lac aux Pin

10 Petite Cascapedia River, Quebec sympatric populations length <150 km high gradient low productivity cold freshwaters warm marine Grand Cascapedia River Petite Cascapedia River brackish water limit BAIES des CHALEURS 10 km

11 Kennebecasis River, New Brunswick sympatric populations trib.. to SJR length <150 km low gradient km high productivity headwaters cold marine warm, low salinity Saint John River head of tide Kennebecasis River brackish water limit KENNEBECASIS BAY 10 km Saint John BAY of FUNDY

12 Nepisiguit River, New Brunswick resident population only 100 km intermediate gradient intermediate productivity cold/cool freshwaters Nepisiguit River Great Falls Outfitters B. Boggan

13 Kennebecasis River 30-Apr Aug Nov Feb Jun Sep Dec Mar Jul Distance upstream (km) Laval River brackish water limit (km 0) individual charr temperature Lac a'jacques radio acoustic counting fence River temperature o C Lac aux Pins Petite Cascapedia R Km Upstream ug Sep-99 9-Nov Dec Feb-00 7-Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr-99

14 headwaters Laval Petite Cascapedia Kennebecasis Summary of movements estuary lower reaches middle reaches winter spring early summer summer late summer (pre-spawn) fall pre-winter

15 Temperatures in the lower river reaches regulates where they can/can t t live Laval Petite Cascapedia Kennebecasis o C Summer Fall Winter Spring

16 Salinity ppt Temperatures and salinities selected by brook charr in the Laval River estuary Apparent limits to distribution at sea Temperature o C 1. Smith & Saunders (1958) Prince Edward Island. 2. Dutil & Power (1980) Hudson Bay. 3. Castongauy et al. (1982) Gaspé Peninsula. 4. Montgomery et al. (1990) northshore, St. Lawrence River. 5. Trites (1960) and Curry et al. (2002) - Kennebecasis Bay. 6. Lenormand et al. (2004) Saguenay River.

17 Kennebecasis and Petite Cascapedia Estuaries 40 Salinity ppt PC estuary/bay - summer 1 4 Kennebecasis 3 estuary/bay 5 - summer Temperature o C

18 Physiological Constraints: 1. Temperature (need for cold water) 2. Poor osmoregulation in marine water, especially cold salt water (C. Audet and students, UQ Rimouski)

19 Variability among tactics: 1. variations in use of estuary and river among populations 2.function of physical environment, river and estuary temperature and salinity, and physiological constraints Salinity ppt Temperatures and salinities selected by brook charr in the Laval River estuary Apparent limits to distribution at sea headwaters middle reaches Laval Petite Cascapedia Kennebecasis Summary of movements lower reaches estuary Temperature o C winter spring early summer summer late summer (pre- spawn) fall pre- winter

20 Variability of tactics (con t): Growth variability among populations 1. advantages of residing in marine habitats (on average) Size of Mature Brook Trout FL (cm) (average BARS ; = min/max LINES = ) F M Petite Casc. Laval Kennebecasis Nepisiguit average FL for New Brunswick streams 2. marine residence isn t necessary to produce larger individuals FL (cm) Laval 1 Kennebecasis 2 Petite 3Casc.

21 Summary of sea-run tactics: sea-run behaviour varies (regulated by habitat) not necessary to grow large and presumably more fit Why go to Sea? - back to our working, alternative hypotheses: a) secondary contact of resident and anadromous genotypes: : predict strong genotypic differences b) anadromous form evolved from residents: - straying residents - low genotypic differences c) resident forms evolving from anadromous forms: - re-colonization and access to headwaters from sea - intermediate genotypic differences

22 a) Secondary contact (anadromous and resident populations)? 10,000 years before present Present Day

23 a) Secondary contact (anadromous and resident popualtions)? LI (freshwater) 100 km/ GULF of MAINE Atlantic and Georges Bank Refugia LAURENTIAN CHANNEL Sable Island Refugia Grand Banks Refuge 12, C yr BP

24 a) Secondary contact (anadromous and resident popualtions)? 100 km/ Freshwater flow Madawaska River Lake Madawaska GULF of MAINE 11, C yr BP

25 a) Secondary contact (anadromous and resident popualtions)? Lake Madawaska Dispersal to ME and Atlantic Canada very limited dispersal of freshwater fishes to the east

26 a) Secondary contact? Larger scale microsatellite DNA analyses among populations a) not 2 distinct genotypes b) northern populations are recently evolved c) neighbouring river populations most closely related (L. Bernatchez and studnets,, Laval)

27 a)secondary contact? - finer scale microsats: : among and within populations ll 3 Rivers Laval Beadle (upstream) Beadle (downstream) Burnthill 10% 17% 17% 16% 84% 66% 20% resident immigrant immigrant (2 nd ) anadromous Stone Origins of young (stable isotopes) 20% 80% South Branch 70% Miramichi 100% Kennebecasis 9% 46% 45% Portagevale 13% 70% PEI 6% Blueshank 17% migratory 42% resident 20% 74% Brookvale 42% 33% 38% Wilmot C 25% 60% 2% Howell s Petite Cascapedia Kennebecasis

28 Back to the working hypotheses: a) secondary contact: - low probability - possible in northern Maine and New Brunswick, central Quebec (yet to be tested) b) anadromous form evolving from resident forms: - very low probability - no freshwater access to entire region during glacier retreat c) residents evolving from anadromous forms = - most probable i) early re-colonization and access to headwaters from the sea ii) neighbour populations most related iii) northern pop ns most recently established iv) intermediate genotypic differences

29 To sea or not to Sea? sea-run tactic better described as partial, facultative anadromy (if anadromy is a necessary descriptor) Why go to sea? - propensity to move and disperse - over-production of juveniles - a residual physiological ability to tolerate saline environments (developed in their phylogeny) - only if critical habitats exist: 1. thermal connectivity in the river and estuary (access to seasonal habitats) 2. coldwater habitats in rivers in summer - large bodied fishes, groundwater 3. ice-free habitats in winter - sea-run tactic is expressed when river conditions permit - not necessarily (perhaps never?) the only evolutionary stable strategy for a river system

30 What does it mean for brook trout in the future? - successful conservation of sea-run populations of brook charr = a) protection of the critical habitats and all their spatial and temporal characteristics. b) habitat limits production of embryos, juveniles, and large adults; consequently, increasing their abundance, e.g., stocking of fish, will most probably have limited success and only in the short-term. term.

31 Acknowledgements L. Bernatchez, C. Audet, F. Whoriskey Many students and staff NSERC ZEC - Petite Cascapédia ZEC - Forestville Aquaculture Forestville La Société de la Faune et des Parcs du Québec McWhirter Family and Staff at Camp Brûlé New Brunswick Department of Natural Resources New Brunswick Environmental Trust Fund Fundy Model Forest Sussex Fish and Game Association Trout Unlimited Canada