Biol. 317 - Lecture notes – Chapter 17 (Oil pollution)


Ch. 17 – Additions of Materials to the Oceans


Additional review questions:


What are the sources of pollution entering oceans?


        shipwrecks, dumping, airborne


What are PAHs and why do they tend to become concentrated in marine sediments?


How does “oil” differ depending on the variety?


What is the behavior of spilled oil?


What are treatments for dealing with oil spills?


Why is there a question about whether or not to spray dispersants on oil spills?



Lecture notes – Chapter 18 (Harvesting the sea)


Fishing adds a predator

        Affects target species

            – largest individuals are taken first

            – average size of individuals decreases


                                    Canadian West Coast ling cod

                                    Peruvean anchovies

                                    South African pilchards

            – not necessarily damaging until size decreases to

                        size of reproductive maturity


        Affects predators of target species


                                    Pinnipeds feeding on pollock in Alaska


        Affects prey of target species


                                    Krill near Antarctica


Fishing can impact non-target species


                                    Pacific squid drift nets and incidental catch

                                                1989 season:

                                                            500 turtles

                                                            4,000 northern fur seals

                                                            14,000 albatrosses

                                                            24,000 dolphins

                                                            186,000 dark shearwaters

                                                            228,000 skipjack tunas

                                                            1,163,000 blue sharks

                                                            1,377,000 albacores

                                                            31,748,000 pomfrets

                                    Pacific yellowfin tuna fishery in 1960s

                                                            200,000 to 500,000 dolphins

                                    Ghost fishing (abandoned gear or nets)


Overfishing – fishing harder than needed

        It is probable that we could catch more fish with less effort in most fisheries


            Maximum sustained yield (MSY)

                        maximum tonnage of organisms that could be taken from a harvested

                        population each year without eventually destroying the population


                        measured in metric tons (tonnes)

            Catch per unit effort (CPUE)

                        tonnage of the catch divided by the amount of effort invested in

                        obtaining it


                        – CPUE goes up quickly in unexploited population

                        – increases until MSY level is reached

                        – then CPUE goes down


                        – best if intermediate-size individuals are selectively taken

                        – this leaves the fewer, larger, individuals for reproduction



                                    plaice prior to WWII


        Global fisheries –

            Are we close to the MSY for all the oceans?


                        – United Nations estimates by Food and Agriculture Organization (FAO)

                        – these do not include “artisanal” catch (taken by individuals for their own

                                    food or for trading)

                        – artisanal catch is estimated to add another 28%


            John Ryther (WHOI) has estimated the productivity of all oceans (Fig. 18-9)

                        – his estimate of 242 million tonnes is approx. 3X 1987 harvest levels

                        – estimates for MSY for all oceans varies from 60 to 100 million tonnes

                        – United Nations assessment from 1987 reports that only 25 of the

                                    280 stocks of fishes worldwide are presently “underexploited”

                                    or “moderately exploited”


            Krill is the most significant stock that is presently underutilized

                        – these are near Antarctica (as unaccessible as they can get, making

                                    their havest costly)

                        – they taste/appear like cooked maggots

                        – market for “fish meal” is uncertain

                        – present high levels are likely a reflection of removal of baleen whales

                        – exploiting these stocks would likely affect the many mammals and

                                    birds that depend on them



                        In terrestrial environments, we vastly increase the amount of food

                                    that is produced by farming

                        Some types of aquaculture have tremendous potential for producing


                                                – even though we get only 2% of our calories from

                                                            the sea, we get 12% of our protein





                                                – both take advantage of tides to bring food/nutrients to

                                                            farmed organisms

                                                – both produce much more protein per unit area than

                                                            comparable farms on land


            Salmon rearing to fry stage is similar in that it takes advantage of the ocean’s



            Other types of aquaculture require 4 to 8 times more protein than they provide


                                    Salmon farming


            Aquaculture can also have many damaging effects



                        compete with native populations

                        introduction of invasive species