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Towards quantifying the structure of the pelagic food web of Northumberland Strait 1 Allan J. Debertin, J.Mark Hanson and Simon C. Courtenay SOUTHERN GULF.

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Presentation on theme: "Towards quantifying the structure of the pelagic food web of Northumberland Strait 1 Allan J. Debertin, J.Mark Hanson and Simon C. Courtenay SOUTHERN GULF."— Presentation transcript:

1 Towards quantifying the structure of the pelagic food web of Northumberland Strait 1 Allan J. Debertin, J.Mark Hanson and Simon C. Courtenay SOUTHERN GULF OF ST. LAWRENCE COALITION SUSTAINABILITY

2 Northumberland Strait What is an Ecosystem?

3 3 Improving Risk-Assessment DFO is moving toward Ecosystem-based- management practices: Improved understanding of ecosystem functions Improved risk- assessment to manage commercial stocks* = EBM requires complex models that focus on multi-species interactions and environmental influences with an overall goal of a sustainable marine ecosystem.

4 mpo.gc.ca/science/Publications/fiveyear-plan- quinquennal/index-eng.html Structure of research for EBM Ecosystem Research Initiatives (ERIs) in areas of concern: 1) Fish Population and Community Productivity 2) Habitat and Population Linkages, 3) Climate Change / Variability 4) Ecosystem Assessment and Management Strategies

5 Why is Northumberland Strait important? Northumberland Strait is a dynamic productive ecosystem Lobster is the most valuable fishery in the area. Other fisheries include: scallop, herring, rock crab, American plaice, mackerel, tuna, cod, winter flounder, white hake, alewife, silversides, smelt, oyster, mussel, quahog, soft shell clam, and Irish moss. Aquaculture of mussels and oysters Tourism and recreational destination – warm summer beaches, boating and sports fishing.

6 Concerns raised by public and industry in Northumberland Strait Declines in commercial fisheries Invasive Species: Green Crab, species of algae and tunicates. Destruction of environment – Scallop dredgers and construction of Confederation Bridge. Deteriorating water quality – sediment deposition, eutrophication, construction of cottages and water barriers. Changes in Climate

7 Before we can begin to understand how human activities impact ecosystem components, we need to first understand how ecosystems function. ? ? ? ? ? ? ? ? ? ?? ?

8 Predator – Planktivorous Fish Bigelow and W.C. Schroeder, Atlantic herring - Clupea harengus Mackerel - Scomber scombrus Alewife - Alosa pseudoharengus Sandlance - Ammodytes americanus Rainbow smelt - Osmerus mordax

9 Prey – Zooplankton and small invertebrates 9

10 Objectives 1)Oceanographic conditions of the Northumberland Strait. – Driving forces of production 2)Distributions of planktivorous fish species and zooplankton. Determine where distinct spatial assemblages occur and if they are explained by environment. 3)Describe the diet composition of planktivorous fish.

11 11 Sampling 11 Data collected in July-August aboard CCGS Opilio (18.2m). Survey since

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19 19 Zooplankton Collection 19 Flow Meter

20 20 CTD Probe Temperature Salinity Density Chl. A Fluor. Turbidity PAR O 2 Conc. Environmental Measurements

21 Data Collected Data Set TypeYear Fish Distribution – Biomass and Abundance Fish Length Frequencies – Abundance Zooplankton Distribution – Abundance + Biomass CTD - Environmental Factors Diet Analysis of Fish Stomachs

22 Objectives 1)Oceanographic conditions of the Northumberland Strait. – Driving forces of production 2)Distributions of planktivorous fish species and zooplankton. Determine where distinct spatial assemblages occur and if they are explained by environment. 3)Describe the diet composition of planktivorous fish.

23 23 Oceanographic Conditions Depth (m)

24 Temperature ( o C) Bottom-water Surface-water Oceanographic Conditions Summer: July-August

25 PAR Turbidity Chlorophyll a Fluorescence Dissolved Oxygen Density Salinity

26 Oceanographic Conditions Chlorophyll a Fluorescence [ g/l]

27 Objectives 1)Oceanographic conditions of the Northumberland Strait. – Driving forces of production 2)Distributions of planktivorous fish species and zooplankton. Determine where distinct spatial assemblages occur and if they are explained by environment. 3)Describe the diet composition of planktivorous fish.

28 Biota Distributions Zooplankton Biomass [g/m 3 ]

29 # individuals/m 3 Large-sized copepods Calanus spp.

30 30 Adult Herring (>22cm) # individuals/ha

31 Crab Zoea Axius-like Pteropods Podon sp. Echinoderm Larvae Evadne sp. # individuals/m 3

32 Crab Zoea Axius-like Pteropods Podon sp. Echinoderm Larva Stage I Evadne sp. # individuals/m 3

33 Patterns in zooplankton composition Multivariate Data analysis – via PRIMER v 6.0 CLUSTER routine. Species assemblages = groups of animals that co-occur in similar patterns which may be influenced by environmental or biotic variables -Determines where most significant change occur in species composition - SIMPROF 33

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35 Assemblage Group Zooplankton Assemblages

36 BEST Routine on Primer w = weighted Spearman rank correlation coefficient 0 = no correlation 1,-1 = complete correlation Variables used: 1 – B. Temperature 2 – B. Salinity 3 – B. Density 4 – S. Temperature 5 – S. Salinity 6 – S. Density 7 - Max Chl. A Fluor.

37 BEST Routine on Primer w = weighted Spearman rank correlation coefficient 0 = no correlation 1,-1 = complete correlation BEST Variable Match No. of Var. Variables w 3 B. Temperature, Salinity, Max CHL A Fluor B. Temperature, Max Chl A Fluor B. Temperature, Density, Max Chl A Fluor B. Temp, Salinity, Density, Max Chl A Fluor B. Density, Max Chl A Fluor B. Salinity, Density, Max Chl A Fluor 0.284

38 BEST Routine on Primer w = weighted Spearman rank correlation coefficient 0 = no correlation 1,-1 = complete correlation BEST Variable Match No. of Var. Variables w 3 B. Temperature, Salinity, Max CHL A Fluor B. Temperature, Max Chl A Fluor B. Temperature, Density, Max Chl A Fluor B. Temp, Salinity, Density, Max Chl A Fluor B. Density, Max Chl A Fluor B. Salinity, Density, Max Chl A Fluor 0.284

39 Rainbow Smelt Mackerel A. Sandlance Gaspereau

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41 Assemblage group Fish Assemblages

42 Discussion Oceanographic conditions in the Strait are complex. There is three dimensional structuring of the Strait, providing different aquatic habitat at small spatial scale. Phytoplankton occurs in highest levels in west and east. Distinct zooplankton and fish communities exist, and there is close spatial association between them. Zonation of biota could provide a means for fisheries managers to determine how detrimental disturbance will influence particular communities of zooplankton and fish. 42

43 Discussion Diet Analysis of Fish – Will provide primary estimate of consumption towards mass- balanced modelling of NS. Other Communities need to be quantified – I.E. Benthic invertebrates in Northumberland Strait. Other Seasons – How does the Ecosystem function in Fall, spring, winter? Need to continue to monitor Northumberland Strait for future changes.

44 Acknowledgements This study would not be possible without the efforts of the captains and crew of the CCGS Opilio, supporting survey staff, and hired students. SOUTHERN GULF OF ST. LAWRENCE COALITION SUSTAINABILITY


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