Stream Residence 1. The choice : emigration vs. residence 2. Food: Abundance, density, and variation 3. Territory and Dominance 4. Fish Responses: Distribution, growth, survival 5. Mortality
Migration is favored when the benefits of being somewhere else exceed the benefits of staying where you are, after correcting for the cost of getting there. Chinook salmon (photo by Roger Tabor)
Emigration of Residence? Emigrate to Sea: Grow fast but face high size selective mortality Stay in Freshwater: Grow slower but face lower predation risk Go early and small: Pink, chum, ocean-type chinook Go late and large: Coho, steelhead, cutthroat, charr, stream-type chinook
Streams: the crux and the curse of salmonid life histories The exclusive or primary spawning habitat for virtually all species, and The exclusive or primary rearing habitat for most species, but The growth of individuals and density of populations depends on leaving the stream Pink, sockeye, and chum salmon liberated themselves from stream rearing, and are the most numerous species.
Abundance of North American anadromous salmonids (millions of adults) chum: 23.7 coho: 13.5 chinook: 5.1 steelhead: 1.6 sockeye: 51.4 pink: 105.5 Salmon: Rogers (2001) 1951 2001; steelhead: Burgner et al. (1992)
Aside: Char(r) seem to have gravitated to a lacustrine (lake-dwelling) way of life Lake trout almost always spawn and rear in lakes Brook trout can spawn in lakes and often rear there Arctic char often spawn and rear in lakes Dolly Varden and bull trout tend to spawn in rivers but can rear in lakes All species can go to sea (rarely lake trout)
Behavioral and population-level perspectives on abundance, density, growth, and survival of salmonids in streams Individual Feeding territory Habitat use Growth Population Abundance Density Variation Movement Survival Population Movement Individual
captured Drifting prey missed missed Maximum capture distance Hughes and Dill 1990 Model of drift-feeding
Coho salmon fry
Streams are heterogeneous, and habitat quality varies, so dominant fish get the best feeding territories. Dropping insects Pool: slow, deep water; low food delivery rate, low energy expense, predation risk?. Drifting insects Riffle: fast, shallow; high food delivery rate, high energy expense, predation risk?
The main prey are small aquatic insects, though there is some shift to larger prey as fish grow: cutthrout trout in the Olympic Peninsula (Martin 1985) 75 % of trout diet 50 25 age 0 age 1 age 2 0 0 to 3 3 to 6 6 to 9 9 to 12 > 12 prey size (mm)
M. Bond Coho salmon fry in a stream, note prominent fin margins
Experimental apparatus for studying territorial competition Food delivery dominant submissive Rhodes M.S. Thesis 1998
Photo: Morgan Bond
Factors affecting dominance relationships among salmonids Body size Metabolic rate Prior claim Experience Sibship Morgan Bond Individual recognition Inter-specific interactions
Foraging success of juvenile coho salmon as a function of social status (Nielsen 1992) Attribute Dominant Subdominant Floater Size (mm) 64 55 50 Foraging rate (bouts/min) Aggression per min Submissive acts per min 2.7 1.8 1.7 0.77 0.42 0.16 0.05 0.21 0.33 Available food (drift + drop) 0.29 + 0.14 0.22 + 0.13 0.06 + 0.15 Growth (mg/d) 5.5 3.2 2.1
Benefits and costs of territories Increased access to food (+) Increased metabolic demand (-) Increased vulnerability to predation (-) Decreased access to food (-) How much territory does a fish need?
Relationship between coho salmon territory size and benthic prey abundance Territory Area (m 2 ) 0.3 0.2 0.1 Dill et al. 1981 20 40 60 Benthos (mg/cm 2 )
Territory size increases with fish size Territory size (m 2 ) 10 3 1 0.3 0.1 0.03 0.01 0.003 Regressions for different salmonids 2 3 5 10 20 30 Keeley and Grant 1995 Fork Length (cm)
Over time, fish grow and so need more food (per capita) but density thins out as mortality takes place. Thus percent habitat saturation may remain constant.
Movement: escape for losers or a chance for the adventurous to get ahead? Conventional wisdom: small, weak, or lateemerging fry cannot obtain territories and move downstream, finding territories or perishing. Recent results: Movement, especially upstream, is common, and reflects poor quality habitat rather than density. Fish may tolerate high density in good habitat and grow slowly. Fish in poor habitat may leave, even if density is low.
Density-dependent growth reduction is evident weight (g) on 15 October 15 12 9 6 3 0 Fransen et al. 1993. Western Washington streams 0.0 0.5 1.0 1.5 2.0 coho salmon per m 2
Prey abundance varies seasonally 10 Invertebrate Drift Frequency (number per second) 8 6 4 2 0 F M A M J J A S O N D Month Bisson et al. Coho Conf.
Rates of food consumption and growth, and temperature experienced by age 1 cutthroat temperature or growth rate (mg/g/d) 14 12 10 8 6 4 2 0 temperature growth consumption Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Bear Creek, Olympic Peninsula, Washington. Martin 1985. 70 60 50 40 30 20 10 0 consumption rate (mg/g/d)
Growth is highly seasonal: good in spring, poor in late summer through winter, good again prior to smolt transformation Mean weight (g) 12 10 8 6 4 2 Huckleberry Creek, WA (samples from several years: from Fransen et al. 1993) 0 0 100 200 300 400 Days after 1 April
Relationship between coho size as parr and smolts Lakes, ponds, and wetlands are often superior to streams as winter habitat Quinn and Peterson 1996. CJFAS
Relationship between mean size of coho and over-winter survival of that cohort % over-winter survival 60 40 20 Carnation Creek 50 60 70 Average Fork Length in September Hartman (1987) In: Salo and Cundy (Eds.) Streamside Management
Little is known about the direct causes of mortality: presumably predation from fishes and terrestrial animals is a large part Maximum size coho salmon eaten by torrent sculpins in aquaria Length Patten 1977. Fishery Bulletin sculpin coho 60 50 80 60 100 70 120 80
Variation in age-1 smolt size among populations % of populations 40 30 20 10 Coho salmon, N = 117 0 Bradford et al. 1997 Weitkamp et al. 1995 70 80 90 100 110 120 130 140 150 160 Age-1 smolt length (mm)
Egg size Fry size Metabolic rate Emergence date Dominance Growth rate Habitat quality Density Movement Survival
Thorpe et al. 1980
Stream Residence 1. The choice : emigration vs. residence 2. Food Abundance, density, and variation 3. Territory and Dominance Factors 4. Fish Responses: distribution, growth, and survival 5. Predation
Prey abundance varies from day to night Samples in May 50 40 30 20 % of total drift 10 Mundie, J.H. 1974. JFRBC 31: 1827-1837 10 16 20 24 4 8 Hours of the day