Oceans and Fisheries Notes

Oceans and Fisheries Notes

1. Introduction

  • Major challenges faced by society today are global/transnational and difficult to solve.
  • Global cooperation needed, as actions may not yield immediate benefits.
  • Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean (2018):
    • First of its kind, it emphasizes understanding fishing impacts before allowing fishing in the region.
    • Sea ice previously acted as a fishing barrier, no longer applicable.

2. Oceanic Ecosystems

  • Oceans are critical for sustaining life and play a key role in global cycles and energy flows.

  • Lack of understanding of ocean ecosystems complicates sustainable use.

  • Limiting factors for ocean life differ from land; nutrients (not water) are most limiting in oceans.

  • Productivity Areas:

    • Coastal zones and upwellings are most productive due to nutrient availability.
    • Depth, temperature, and light are also limiting factors; productivity generally lower below 200 meters.

  • Euphotic zone:

    • Warm and light-rich surface waters support higher productivity.
    • Transition to cooler waters is marked by the thermocline (120-240 meters depth).

  • Deep Sea Characteristics:

    • Over 9,000 meters deep, but most (75%) between 4,000 and 6,000 meters.
    • Fisheries concentrated on continental shelves, especially within the top 100 meters.

  • Carbon Cycle in Oceans:

    • Oceans absorb CO2, with significant research on carbon balance and acidification.
    • Acidification: CO2 combines with water, forming carbonic acid ($H2CO3$), increasing acidity.

  • Thermohaline Circulation:

    • Oceans currently about 30% more acidic than pre-industrial times, impacting fisheries.
    • Circulation driven by density differences from temperature and salinity variations.
    • Melting polar ice may disrupt circulation, with potential for a new ice age.

  • Coral Reefs:

    • Known as the rainforests of the sea, coral reefs are essential for biodiversity.
    • Composed of coral polyps and symbiotic algae ($ ext{zooxanthellae}$).
    • High temperatures can cause coral bleaching, leading to death of corals.

3. Ocean Management Challenges

  • Main challenges include fisheries, pollution, coastal development, and climate change.

  • Fisheries:

    • Most important fishing grounds found along continental shelves (<370 km from shore).
    • Fisheries provide ~20% of global animal protein; fish populations are declining, with smaller catches.

  • Pollution:

    • Oceans serve as the ultimate sink for many pollutants, with impacts from chemicals and nutrients.
    • Endocrine disruptors pose serious risks, with consequences like feminization in aquatic species.
    • Oxygen depletion leads to hypoxia, creating dead zones, particularly near coastal areas.

  • Climate Change:

    • Global warming results in sea level rise (250mm between 1870-2013) and increased ocean temperatures.
    • Predicting an ice-free Arctic by century's end, affecting species dependent on ice.

  • Coastal Development:

    • 21 of the world's 33 mega-cities are coastal, leading to habitat loss and resource depletion.
    • Fragmented environmental management complicates decisions regarding coastal ecosystems.

4. Global Responses

  • International efforts are crucial; the United Nations Convention on the Law of the Sea (UNCLOS) provides a legal framework since 1994.

5. Canada’s Oceans and Fisheries

  • Canada has the longest coastline and the second-largest continental shelf; managed by the Department of Fisheries and Oceans (DFO).
  • Canada's fisheries resources are governed by the Fisheries Act, which is currently outdated.

6. Aquaculture

  • In response to declining wild fisheries, aquaculture is the fastest-growing food production sector, accounting for nearly half of global fish production.
  • Concerns about aquaculture include: escapement, disease, lice, pollution, and social impacts.