Presentation on theme: "Long-term shifts in faunal assemblages in Eastern North America Introduction to the ERF Special Session SCI 050 Chairs: Rodney Rountree (Marine Technology."— Presentation transcript:
Long-term shifts in faunal assemblages in Eastern North America Introduction to the ERF Special Session SCI 050 Chairs: Rodney Rountree (Marine Technology and Ecology Applications, Inc.) Francis Juanes (Dept. Natural Resources Conservation, UMass Amherst)
Long-term Shifts in Faunal Assemblages in Narragansett Bay, Rhode Island With Joachim Gröger, Institute for Sea Fisheries, Hamburg, Germany
Analysis Based on RIDEM Seasonal Trawl Survey Massachusetts Rhode Is. <20 ft >20 ft 1300 tows 1979-2001 20 minutes at 2.5 knots Two depth strata effort proportional to strata area
Benthic fishesPelagic fishes 79-83 84-88 94-9889-93 99-01 72% 15% Assemblage shift in Narragansett Bay
Narragansett Bay Trend Suggests Eutrophication Effects But….
… Similar Shifts have been observed on Georges Bank and attributed to fishing effects M. Fogarty, NMFS, NEFSC Shift between benthic and pelagic mid-1980s
Possible causes of observed assemblage shift 1)Regional warming and the invasion of warm water fishes such as scup 2)The release of limited food resources to transient species due to the decline of winter flounder 3)Overfishing of key species 4)Eutrophication 5)Habitat loss 6)Other human impacts (local and regional) 7)Natural cycles
0.0 25.0 50.0 75.0 100.0 12345 Normalized Mean CPUE in Narragansett Bay Urophycis chuss Declining Urophycis regia Increasing No change Raja spp.
Number of species exhibiting significant temporal changes
Cant see the forest for the trees
So look at how similar trees cluster together. Cold water benthic – scavenger? Pelagic - planktivores increasing Piscivores (benthic and pelagic) or warmwater demersal Increasing/no change Benthic feeding fishes – warm and cold decreasing
Species type category Species Percent hauls HabitatTempExploitedFeedingSpawning Linear trend P. americanus84benthiccoldwateroverbenthicestuarinedecline S. aquosus62benthictemperatenonbenthicshelfdecline S. chrysops49demersalwarmwateroverbenthicshelfincrease L. pealeii48pelagictemperateoverzoo- plankton shelfincrease H. americanus48benthiccoldwateroverbenthicshelfincrease M. canis5benthictemperatenonbenthicestuarinenone Characterize 32 species type and annual trend
Planktivores - tend to increase Benthic feeders - tend to decline Piscivores - increase or decline
Cold water fish – tend to decline Warm water fish – increase or decline
Benthic fish – tend to decline Demersal – no change or decline Pelagic – tend to increase
-0.6 0.6 0.4 -0.4 0.2 -0.2 0.0 Decline Increase No change Freshwater spawner Estuarine spawner Shelf spawner Under exploited Over exploited Demersal habitat Pelagic habitat Benthic habitat Temperate Warm water Coldwater Piscivore Zooplanktivore Benthic feeder
Conclusions Multivariate analysis of Narragansett Bay fish community change suggests: Strongest patterns are related to trophic source - fishes depending on benthos for food are most likely to decline - fishes depending on plankton for food, or piscivores indirectly depending on plankton, tend to increase Secondarily, estuarine spawning fishes tend to decline, while freshwater or shelf spawners are increasing or not changing Thirdly, cold (northern) water fish tend to decline, while southern fish tend to increase
Benoit and Swain. Gulf of St. Lawrence (Fish & Inverts) Able and Sullivan. Little Egg Inlet, NJ (Ichthyoplankton) Allen, Ogburn-Mathews and Tracy. North Inlet, SC (Zooplankton and nekton) Mitchell, Buckel, Taylor, Bathand Shertzer. Beaufort Inlet, NC (Ichthyoplankton) Keenan, Matheson, Switzer,Greenwood and McMichael. Tampa Bay, FL (Nekton) Broad-scale Studies: Hale. Coastal Delaware to Maine. (Benthic Inverts) *poster Chmura, Van Guelpen and Pohle. Coastal marine Florida to Canada (Modeling) Four Southern New England Studies: Rountree and Juanes. Narragansett Bay (Fish) Lynch and Lee. (poster) Narragansett Bay (Fish) Danila and Landers. Millstone, Long Island Sound (Fish & inverts) Whitlatch and Osman. Southern New England. (Benthic inverts) OConnor and Juanes. Hudson River (Fish) *Student Chant. New York Bight (Oceanography) Five Chesapeake Studies: Ruck*, Kraus, Chris and Kelso. Potomac River. (Fish) *Student Aguilar, Hines, Kramer and Goodison. Rhode River, Upper Ches. (Fish) Wingate and Secor. Mesohaline Ches. (Fish) *Poster Breitburg and Cottingham. Chesapeake Bay. (Stressors) Kimmel and Newell. Ches. Bay. (Oysters) *Poster Can we use similar methods to compare temporal patterns among a wide range of geographic areas and taxa to determine the most likely major causes of observed assemblage shifts?
Acknowledgements Woods Hole Sea Grant College Program for travel support
Thank you! Http://www.fishecology.org
Spatial Comparison Massachusetts Rhode Is. Mt. Hope Bay 3 1 2 4 5 6 7 8 9 3 1 2 4 5 6 7 8 9 Greenwich Bay Upper Narragansett Middle West Passage Middle East Passage Upper Sakonnet West Passage East Passage Lower Sakonnet