Fish Conservation and Management CONS 486 Ocean ecosystems Ross Chapter 2
Topics Physical/temperature zones Magnitude/types of currents
Major theme: Linking science to conservation & management Physiology Behaviour Population ecology Ecosystem ecology Habitat data (limnology, oceanography) Life history Basic science Applied science Fisheries exploitation data Applied life history data Human dimensions: socioeconomic data Protecting populations & habitats Restoring populations & habitats Conservation Management Harvest regulations Managing fisheries & habitats
Introduction Oceans share many similarities with lakes Physical attributes to lakes; e.g., zonation Ecological attributes of lakes; e.g., food webs Lakes and oceans physically differ (and as a result ecologically differ) with respect to: The size of physical/temperature zones The influence of currents, tides
Introduction Standard aquatic food web applies Bottom up and top down influences affect patterns of abundance in marine populations Littoral areas: structure and cover are important habitats for many fish to feed, rear and spawn Pelagic areas: home to phytoplankton, the main pelagic energy producer Fed upon by zooplankton Who are in turn eaten by other zooplankton and fish
Oceanographic scale: Size matters Littoral area in flux: intertidal zone Near shore habitat changes w/ tidal influence Continuously mixed by winds & tides Sub littoral area: Portion of littoral that extends to the edge of the continental shelf (~200 m depth) In some places in the world extends out from shore as much as 1000 km
Neritic zone: littoral + sub littoral
Oceanographic scale: Size matters Pelagic area: can be considered high seas, open ocean Epipelagic area: Mixed layer Upper 200 500 m Note: term epilimnion is incorrect: limnion means lake
Pelagic zone
Pelagic/Epipelagic fish: Bluefin tuna
Pelagic fish: shortfin mako (Isurus oxyrinchus)
High water (tidal) Continental shelf Pelagic zone Neritic zone Low water (tidal) Epipelagic zone Littoral zone (intertidal) Sub littoral zone
Temperature and thermocline Not always tropical: < 10% of ocean environments are warmer than 10 C Most water is below thermocline Thermocline: A permanent thermocline exists Isothermal at 4 5 C in temperate zone Permanent: cannot be broken by strong winter winds as in most lakes Due to combined density effects of temperature and salinity
High water (tidal) Continental shelf Pelagic zone Neritic zone Low water (tidal) Epipelagic zone Littoral zone (intertidal) Sub littoral zone Permanent thermocline 4 5 C 200 500m 10 000m
Temperature and thermocline In temperate zones Seasonal thermoclines can exist Like in lakes Usually at 50 200 m depths Surface mixed layer is 14 16 C in summer Seasonal thermocline at ~ 11 12 C in temperate zones
High water (tidal) Continental shelf Pelagic zone Neritic zone Low water (tidal) Epipelagic zone 14 16 C Seasonal thermocline 11 12 C 50 200m Littoral zone (intertidal) Sub littoral zone Permanent thermocline 4 5 C 200 500m Typical summer temps in temperate climate 10 000m
Ocean currents
Major currents Major surface currents are primarily wind driven Related to major wind systems Large rotating current systems are called gyres Spiral or vortex Result from wind, planetary motion, and friction Because of earths eastward rotation, major currents which move westward at the equator, are deflected to the right in the northern hemisphere and to the left in the southern hemisphere
Major currents Confirmation of the Coriolis Effect Not convinced, Bart calls Australia to confirm their opposite drainage direction https://www.youtube.com/watch?v=l7x_cmt5tru
Major currents can be quite fast 2 m/s Kuroshio Current and Gulf Stream 1 m/s Alaskan Current 0.2 m/s California Current Figure 2.9 From Ross
Gulf stream current pattern U Miami
Gulf Stream temperature Labrador current Gulf stream Florida
Major current patterns and climate major current patterns affect regional climate e.g. the Gulf Stream heats the north Atlantic making Ireland the emerald Isl Newfoundland is at the same latitude as Ireland but receives none of the heat benefits so is much colder and has shorter growing seasons Coastal Ireland Coastal Newfoundland
Major current patterns and climate change Climate change could result in polar and equatorial temperatures being more similar Ocean currents like the Gulf Stream would slow in speed Would result in less heat transfer from equator towards poles Could actually result in regional cooling, as well as other large environmental changes!
Regional surface currents can be complex Gulf Stream seen at bottom River influences E.g., St. Lawrence Coastal inlets and bays Resulting eddies (bottom right) Counter current flow patterns
Density driven currents: Upwelling Currents also affected by water density Higher salinity, or cooler temperatures = more dense Lower salinity, or warmer temperatures = less dense Where wind driven currents encounter less dense water (eg near a river mouth or warm climate) upwelling can occur Where wind driven currents encounter more dense water, downwelling can occur Upwelling brings nutrient rich deep water, and organisms, to the surface and are the locales for some of the worlds most productive fisheries
Cold open ocean currents encountering hot coastal climate
Upwelling current patterns and climate The California Current upwelling keeps northern California coast cool all summer Cool coastal temperature clashes with warm inland air temperatures Coast 20 C whereas a few km inland its 38 C Summer fog banks keep the coast cool The coldest winter I ever spent was a summer in San Francisco Golden Gate Bridge San Francisco, CA
Role of coastal habitats to fishes Biological production is greatest in coastal areas & continental shelf Especially upwelling zones Fish production is greatest here Where many of world s largest fisheries occur E.g., sardine, mackerel, anchovy, hake
Pacific sardine (Sardinops sagax)
Atlantic mackerel (Scomber scombrus)
Anchovy (Family Engraulidae)
White hake fisheries
Role of currents to fishes Currents affect abundance and distribution of fishes Can vary by life stage Advection of young: evolved behaviours that utilize current patterns to enhance juvenile survival E.g. plaice lay demersal eggs in optimum spawning habitat Emerged juveniles are advected to areas ideally suited for rearing
Trying to find my plaice in life
Seems like a nice plaice to grow up
Find your own damn plaice!
Tidal driven currents Tides: result of gravitational pull of moon (and sun) on earth s surface, and earth s own rotation Change in water levels on ~24 hr 53 min cycle Up to 3 m amplitude in our region, varies globally Bay of Fundy = 17m! basin shape & tidal resonance Generate many different habitat types due to water rising, falling, & mixing Including
Tidal influenced habitats: salt marsh
Tidal influenced habitats: mud flats Fiddler crab (Uca spp)
Role of surface & tidal currents: coastal migrations and salmon fisheries Fraser sockeye hold in Georgia Strait until high tide (red circle) Migrate up river when currents less energetically costly Johnstone Strait Strong Alaskan currents cause more salmon to migrate through Johnstone rather than Juan de Fuca Strait (red lines) currents affect where and when fisheries openings occur affects whether harvest is by US or CDN fishers!! Canadian Geographic
Going coastal Estuaries and salt marshes near the mouths of rivers are extremely important habitats Freshwater pours over the salt water causing entrainment of nutrients into the mixed area This stimulates plankton production The river deposits many of its own nutrients and floating organic matter Stimulates biological production and fish foraging E.g. outmigrating salmonids These habitats often degraded by human activities Locations of cities, where watershed effluent ends up
Important coastal habitats for fish http://www.inlandbays.org/ Sea grass beds: marine fields
Important coastal habitats for fish Kelp beds: marine forests
Coming up next We get caught up in Fisheries exploitation!