Pg. 92 RTW: What is one problem caused by invasive species? Objective: I will be able to describe the consequences of biodiversity due to invasive species and their effects on the marine ecosystems and their modes of introduction. Agenda: Gallery Walk Invasive Species (pg. 89) GOW Pg. 90 TOC Pg. 91 Homework: Study for Invasive/Overfishing Quiz on Friday Monday, February 8 th
Pg. 92 RTW: Should we kill invasive species? Objective: I will be able to describe methods of commercial fishing and their impact on the world’s oceans. Agenda: Tragedy of the Commons Lab Homework: Study for Invasive/Overfishing Quiz on Friday Tuesday, February 9 th
Pg. 92 RTW: What is the tragedy of the commons? Give an example of a public/global common Objective: I will be able to describe methods of commercial fishing and their impact on the world’s oceans. Agenda: Overfishing notes pg. 93 Homework: Study for Invasive/Overfishing Quiz on Friday Wednesday, February 10 th
Overfishing
Some of the Most Exploited Fish Stocks: Cod Tuna Sharks Grouper Swordfish
Maximum Sustainable Yield = the maximum level at which a natural resource can be routinely exploited without long-term depletion. Currently we are exploiting our fish stocks to such an extent that experts expect that the fishing industry will collapse by 2050!
The Consequences
Pg. 92 RTW: List the most threatened fish stocks. Objective: I will be able to explain the concept of overfishing in terms of maximum sustainable yield and cite examples of overfished stocks. Agenda: Overfishing Notes (pg. 93) Homework: Study for Invasive/Overfishing Quiz on Friday Thursday, February 11 th
Different Fishing Methods Gill nets Purse seine nets Trawling Long lines Drift nets
Different Fishing Methods
Gill Nets
Gill nets are vertical panels of netting normally set in a straight line. Fish may be caught by gill nets in 3 ways : 1. wedged – held by the mesh around the body 2. gilled – held by mesh slipping behind the opercula 3. tangled – held by teeth, spines, maxillaries, or other protrusions without the body penetrating the mesh. Mesh size, twine strength, as well as net length and depth are all closely regulated to reduce bycatch of non-target species.
Purse Seine Nets
A purse seine is a large wall of netting deployed around an entire area or school of fish. The seine has floats along the top line with a lead line threaded through rings along the bottom. Once a school of fish is located, a skiff encircles the school with the net. The lead line is then pulled in, "pursing" the net closed on the bottom, preventing fish from escaping by swimming downward.
Trawling
Trawls are nets towed behind a boat to collect organisms. Trawls can be divided into three categories based on where they sample the water column: 1. Surface 2. Midwater 3. Bottom
Long Lines
Long lines use a long line, called the main line, with baited hooks attached at intervals by means of branch lines called snoods. Longlines can be set to hang near the surface (pelagic longline) or along the sea floor (demersal longline)
Drift Nets
Drift nets hang vertically in the water column without being anchored to the bottom. The main difference between gill nets and drift nets is whether or not they are anchored to the bottom.
Drift Nets vs Gill Nets
Problems with Fishing Methods Bycatch= the unwanted fish and other marine creatures caught during commercial fishing for a different species. Trawling methods can damage coral reefs and other ecosystems Unsustainable
Solutions? Reduce bycatch with alternative gear (turtle exclusion hatch or circle hooks) Use sustainable methods Aquaculture= raising fish similar to livestock
Buoy Caught Swordfish Sustainable Fish Need for Sustainable Fishing
Pg. 92 RTW: Name one type of fishing method and how it negatively impacts the oceans. Objective: I will be able to explain the concept of overfishing in terms of maximum sustainable yield and cite examples of overfished stocks. Agenda: Quiz on Invasive Species/Overfishing Shark Finning Homework: None Friday, February 12 th
What if There Were No Sharks Shark Fin CSI Shark Finning