Life Beyond the Spawning Grounds: Distribution & Food Web Relations of Herring & Forage Fishes in Puget Sound Dave Beauchamp, USGS & UW-SAFS Liz Duffy, UW-SAFS (NRDC) Iris Kemp, UW-SAFS Collaborators: DFO-Canada: Dick Beamish, Rusty Sweeting, Chrys Neville Funding: HSRG, Pac. Salmon Commission
Most Forage Fish Data Currently derived from Spawning Surveys Trends in spawner biomass, ~age structure, growth & survival estimates by stock & geographic region (e.g., Stick & Lindquist 2009) Less information available regarding ontogeny, seasonal diet, distribution, trophic interactions Environmental & ecological factors affecting survival & growth: Predation Competition Food supply Climate forcing? Water quality? Contaminants?
Exploit Similar Info-Needs for Juv. Salmon & Forage Fishes Most life stages can be sampled with the same gear at the same times & locations during the growing season Methodically record data & archive samples of non-target species (freeze) Break down salmon v forage fish silos in research, monitoring & restoration Benefit from economies of scale
Objectives Summarize some data collected opportunistically (2001-present): Epi-pelagic distribution & Relative abundance Diet, diet overlap, competition, predation Highlight opportunities for joint R&M efforts to address juv. salmon survival & forage fish questions: Temporal-spatial distribution Food web interactions Stage-specific growth & survival
Data Sources DFO-Canada Midwater Trawling July & Sept. cruises ~2001-2013 Depth-stratified samples in N & C basins: 0-15m, 15-30m, 30-45m, 45-60 m Future Cruises are highly uncertain beyond Sept. 2013 NPS CPS ** -Beach Seining 2001-2002 N, C, S basins, Apr-Sept -Pilot Purse seining ** June 2003 Mukilteo-Clinton SPS
Herring: Nearshore-Offshore Size Structure Fl Bins (mm) Ontogenetic & Seasonal shifts In near-offshore Habitat use & Size structure Proportion 0.4 Nearshore 2001 July 2001 Sep 2001 0.3 0.1 0.4 Nearshore 2002 July 2002 Sep 2002 0.3 OFFSHORE CHINOOK LENGTHS August Sept May-July July Sept 0.1 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230
Offshore Catch Proportions 1.00 Summer 35,365 8 tows 5,547 12 tows July 67,255 12 tows 28,127 16 tows 17,176 11 tows 4,922 13 tows Herring catches represent a volatile underestimate of spp composition due to patchy encounters with schools during Daylight tows Forage fish abundance trends from these data are dubious BUT Proportion of Catch Depth distribution patterns useful 0.75 0.50 5 0 Excellent source of biological data! 1.00 0.75 0.50 Fall 15,824 16 tows Coho Herring Chinook Herring Pink Chum 6,795 14 tows Sept 3,191 14 tows Chinook Pink 35,747 15 tows 4,080 10 tows 2,810 12 tows Chum Pink Chinook Coho Herring Other Relative abundance & distribution Data for juv. salmon considered More reliable than for herring 5 0 Chum 2000 2002 2004 2006 2008
Split-beam Hydroacoustics 2002 0-15 Targets 60-284mm Depth (m) 15-30 30-45 July August September 45-60 0.1 0.3 Density (Targets/1000m 3 0.4 0.5 )
Abundance & Spatial-Temporal Overlap of Potential Pelagic Competitors Daylight Planktivore Community Herring dominated the Biomass of epi-pelagic Planktivores during Critical July growth period 15 Mean Catch/hr 0 5000 10000 15000 20000 25000 30000 35000 All planktivorous fishes Concentrated in 0-15m During July. Depth (m) 30 Chinook Other Salmon (30% pink salmon) Herring Other Spp 45 60 July 2004 DFO Ricker Midwater trawl
Purse Seining: Live Capture of Pelagic Salmon
Epi-Pelagic Fish Community Sampled with Purse seines Juvenile salmon & forage fish Prevalent in epi-pelagic zone Catch per Haul 100 80 60 40 20 June 2003- Daylight purse seining Purse seine, June 2003 Whidbey-Mukilteo W Chinook H Chinook Coho Chum Dusk Forage fish abundance MUCH HIGHER than juv salmon Surf Smelt & Herring dominate The epi-pelagic catch Surf smelt densities seem higher Closer to shore slope than in mid-channel Smelt rare in Ricker MW Trawls Catch per Haul 0 2000 1500 1000 500 0 W Chinook H Chinook Coho Chum Herring Smelt 26 180 200 30 200 West Bottom Depth (m) East Dusk
DAYLIGHT: Mukilteo (7:38pm) to Possession (7:57pm) 60 m
DUSK: Whidbey by Clinton Ferry 9:36-9:45pm 60 m
Summer Herring Diet by Size class, Year, and Month Volumetric proportion 1.2 1.0 0.8 0.6 0.4 PS Offshore Herring Diets (<130 mm) July n = 10 58 mm n = 4 92 mm 1.2 1.0 0.8 0.6 0.4 PS Offshore Herring Diets (>130 mm) JULY n = 7 190 mm n = 11 162 mm n = 10 170 mm n = 7 153 mm COPEPOD CRAB LARVAE EUPHAUSIID GAMMARID HYPERIID OSTRACOD CHAETOGNATH LARVACEAN INSECT OTHER Volumetric proportion 1.2 1.0 0.8 0.6 0.4 Sep COPEPOD CRAB LARVAE EUPHAUSIID GAMMARID HYPERIID OSTRACOD CHAETOGNATH LARVACEAN INSECT OTHER n = 5 110 mm 1.2 1.0 0.8 0.6 0.4 SEP 2001 2004 2008 2009 n = 9 167 mm n = 8 164 mm n = 10 180 mm n = 4 188 mm 2008 2009 2001 2004 2008 2009 Small herring feed more heavily on Copepods than older herring Larger herring eat more crab larvae & amphipods
Winter Herring Diet by Size class, Year, and Month 1.2 PS Winter Offshore Herring Diets <130 mm 1.0 n = 12 109 mm 0.8 0.6 0.4 1.2 1.0 COPEPOD CRAB LARVAE EUPHAUSIID GAMMARID HYPERIID OSTRACOD CHAETOGNATH LARVACEAN INSECT OTHER >130 Mar mm 2008 Feb 2010 n = 6 201 mm n = 16 184 mm 0.8 0.6 0.4 Mar 2008 Feb 2010 Small herring feed more heavily on Copepods than older herring Larger herring eat more amphipods
Strong Diet Overlap during Critical Growth Period Between juvenile Salmon spp. and Herring Key Prey Overlap: Crab Larvae Hyperiids Euphausiids JULY Key Prey & degree of Diet overlap Vary among years 1.2 1.0 0.8 0.6 0.4 1.2 Chum Salmon show Least overlap with Other salmon & herring 1.0 0.8 0.6 0.4 2004 2008 n = 143 157 mm Chum n =125 133 mm n = 216 132 mm n = 139 182 mm Chum Pink Herring Chinook Coho n = 120 160 mm n = 90 120 mm n = 11 162 mm n = 10 170 mm n = 178 136 mm n = 99 201 mm Pink Herring Chinook Coho Insect Gammarid Hyperiid Crab Larvae Copepod Euphausiid
Herring Size-at-Age (from Stick & Lindquist 2009) 100 Body Mass (g) 80 60 40 SPS CPS NPS 20 0 0 1 2 3 4 5 Age
Potential Inter-specific Competition for Food Herring remove 10-47x more Biomass of key shared prey than H+W Chinook during Critical May-July period CONCLUSION: On average, Competition driven 1 o by Herring in pelagic Habitats of Puget Sound. Prey consumption demand (MT/season) 20000 18000 16000 14000 12000 10000 But-Competition should be Considered across the entire Epi-pelagic planktivore community 8000 6000 4000 2000 0 37x Copepod Crab Larvae Population-level consumption demand 2008: SPS, CPS, NPS 10x 45x Euphausiid Gammarid by Herring age 0-4 by Chinook age-0 47x Hyperiid Other Intensity of competition will likely Vary among regions & months, based on relative abundance & diet of each species
Exis%ng Knowledge Epi- Pelagic plank/vore community biomass dominated by herring Significant diet overlap between Herring and Juvenile Chinook Herring consume 10-40x the biomass of prey shared by Chinook Poten/al for considerable compe//on effects on growth Other salmon and forage fishes also overlap and compete, but impose lower consump/on demand than herring
Conclusions & Recommenda/ons Consider Carrying Capacity for en/re plank/vorous fish community rather than for single species Considerable diet overlap among Herring & juvenile salmon. Less know about other forage fishes Forage fish biomass & dynamics can poten/ally overwhelm trophic effects of juv. salmon Must consider interac/ons at proper temporal- spa/al scales Compe//on could vary significantly among regions, months, & years Need zooplankton data!!
Predators
Sea-run Cutthroat Trout Spring-Summer Diet by size class 150-250 mm Cutthroat trout Relatively low abundance Primarily a nearshore predator Smaller Less Piscivorous trout Eat juv. salmon & sandlance Larger (FL > 250 mm) trout are Highly piscivorous and primarily eat Herring & juv Salmon Diet Proportion by Wt Diet Proportion by Wt 1.0 0.8 0.6 0.4 1.0 0.8 0.6 0.4 May 250-450 Junemm Cutthroat July Aug trout Sept Invert Salmon Chum Chinook Coho Sandlance Herring OthFish May June July Aug Sept
Predatory Juvenile & Resident Chinook Salmon Relatively abundant predator Feed in Nearshore & Offshore Habitats Nearshore predation by juveniles primarily in June-July Offshore predation year-round by Resident & older juvenile Chinook
Frequency 40 30 20 Size-selective Predation Puget Sound Chinook in midwater trawls 2001-2009 150 100 Prey Size : Predator Size Nearshore 2001-2003 50% 50% Predator L Chinook Chum Pink Salmon Sand lance Herring Bay pipefish Perch Stickleback Fish Sample Proportion 10 0 300 350 400 450 500 550 600 650 700 0.4 0.3 0.1 Piscivore Size Distribution Fork length (mm) Size-selective cannibalism: Sizes of age-0 Chinook eaten vs available Offshore in July 90 100 110 120 130 140 150 160 170 180 Fork length (mm) Eaten Available Prey fish FL (mm) 50 0 150 100 50 0 Offshore 50% 2001-2007 50% Predator L 0 100 200 300 400 500 Chinook FL (mm)
Size-selective predation on Herring by Juvenile & Resident Chinook Salmon Sample Proportion 5 0 0.15 0.10 5 0 0.15 0.10 5 A B Age-0 Chinook prey Herring in trawl 0 Age 1-3 Chinook prey Herring in trawl 0 40 60 80 100 120 140 160 180 Fork length (mm) Herring found in age-0 Chinook stomachs are significantly smaller than those sampled Concurrently with MW Trawl Same for larger resident Chinook
Size-selective predation by Chinook on Sand Lance is less evident Sample Proportion 0.5 0.4 0.3 0.1 0.4 0.3 0.1 A B Sand lance Age-0 Chinook prey Sand lance in trawl Age 1-3 Chinook prey Sand lance in trawl 40 60 80 100 120 140 160 180 Fork length (mm)
Simulated Predation Demand by Resident Chinook in Puget Sound FL > 300 mm Population Consumption (MT) 400 300 200 100 0 Chinook Pink & Chum Herring Sand Lance Other Fish Inverts May June July Aug Sep Oct Fall Win Apr Month - Season -Herring are the predominant prey of Chinook >300 mm throughout the year -Over 1,500 metric tons of herring consumed by resident Chinook annually in PS
Other predators Harbor Porpoise & Harbor Seal populations have increased significantly over recent decades Piscivorous birds? Demersal fishes?
Exploit Similar Needs for Ecology of Juv. Salmon & Forage Fishes Much to be learned about how food web processes & environmental factors limit forage fish: Seasonal food supply & demand Competition Predation mortality, Disease Most life stages can be sampled with the same gear Ichthyoplankton sampling an important exception Methodically record data & archive samples of non-target species (freeze) Break down salmon v forage fish silos in research, monitoring & restoration Benefit from economies of scale