Key Points from Shark Article!

Group 1: Lark, Sam, Emily, Erin Ecological Features ●Inhabit all areas of ocean, from fully oceanic to being limited to shallow reefs and continental shelves, and some that transition between the two. ●Life History - Life cycle of growth, sexual maturity, reproduction, and offspring rearing o Slow growers and reproducers. This prevents sharks from recovering quickly from population depletion since they reach sexual maturity late in life, and do not have large numbers of offspring. ●Sharks occupy different levels of the food chain- some are top predators while others are mesopredators ●Generalist feeders- mostly carnivores, but some planktivores ●Because their feeding is not gape-limited, they are often the major or exclusive predators of megafauna

Group 2: Eva, Robin, Miles, Thea Figure 2. Global fisheries trends and conservation status of chondrichthyans. Time series refer to landings of sharks, rays and chimeras in thousands of metric tonnes km -2 of shelf area since 1950, until Red bars=% of species in certain area that are globally assessed as critically endangered (CR), endangered (EN), and vulnerable (VU) Yellow bars=yellow indicates near threatened (NT) status and green the percentage of species assessed as least concern (LC). Green bars= species that are the least concern Transparent bars= species that are assessed data deficient (DD) or that have not been assessed yet n = total species in area, A = number of species assessed ●For the most part, all areas have upward trends, except for China, and areas in Northern Europe... which appear to be pretty constant. ●Many areas have drops around the 1970’s and 1980’s. ●In South America, there is a lot of variation between years. ●In Western Africa, a huge increase in the mid-1990’s.

Ferretti et al.

Group 3: Nate’s :9, Jeff, Sophia, Caitlin Coastal Ecosystems (Closest to the shore, no more than 200 m deep): ●Highly accessible, lots of human activity→ exploitation ●High biological productivity ●Been fished since humans lived in coastal regions Demersel Ecosystems (Continental shelf and slopes): ●Home to 90% of elasmobranch species (Sharks, rays, and skates) ●Trawl fishing→ dragging a big net ●Shrimp fisheries with a lot of elasmobranch by-catch ●Fished by bottom trawling since the 1970s Pelagic Ecosystems (Open ocean, deep waters): ●Industrial fishing since the 1950’s ●Long-line fishing for tuna, swordfish, and other large fish ●Known for large amounts of sharks as by-catch (1 shark for every 2 yellow- fin)

Group 4: Effects on Elasmobranch Mesopredators ●Mesopredator: a medium-sized predator which often increases in abundance when large predators decline. ●Decreases in large sharks usually lead to increases in elasmobranch mesopredators (i.e. dogfish and other small sharks). ●This is better documented in coastal habitats than in pelagic (open sea) habitats. o Some increases reported in pelagic habitats but effects have also been attributed to:  Declines in other open sea apex predators (i.e. tuna)  Changes in habitat use, allowing mesopredators to move into waters previously dominated by larger sharks. ●Elasmobranchs are highly sensitive to fishing, so any increases in fishing would seriously impact mesopredator populations despite their recent increases in abundance. ●Example: dogfish have increased 20- and 17-fold in the Gulf of Alaska and Prince William Sound, and S. megalops has increased fivefold in Australian waters from ’76–’97. Toby, Gabe, Andrew, Ruth Dogfish%20Pictures.htm

Group 5: Dani, Evan, Lisa Effects of Shark Exploitation on Marine Mammals and Sea Turtles: ●Decrease of sharks increase range of marine mammals and sea turtles ●Reduced shark predation on juveniles increase marine mammal and sea turtle populations ●Increased population sizes of marine mammals and sea turtles create competition within and between species (trophic cascade) ●Increased population sizes of marine mammals and sea turtles decreases the amount of seagrass left (trophic cascade) ●Marine mammals tend to avoid areas of high predation risk, but sea turtles tend to remain in seagrass beds with high predation risk

Group 6: Jake, Emma, Emilee ●Removal of large sharks results in trophic cascades o Large sharks eat the rays and small sharks, the small sharks then eat the bony fish (see figure on the next slide). ●Large sharks were netted off the coast of South Africa for 50 year ●When large sharks were originally netted, that resulted in an increase in small sharks and a decrease in bony fish ●When small sharks began to succomb to angling pressure, the population of bony fish increased again ●Sharks can also influence other marine ecosystems, such as those that contain seagrass and grazers like turtles and dugongs ●More research needs to be done to determine if this is an isolated effect or if it might be seen in another ecosystem; there simply isn’t much research on non-commercial sharks.

Group 7: Lily, Kristen, Amy :Conclusion ●visibility/public opinion in terms of conservation ●sensitivity to ecosystem change, even ‘sustainable’ fishing ●trophic cascade: increase in mesopredators ●low reproductive rates increase risk ●wide range mobility makes observation difficult ●because the ocean is a complex system, it is difficult to discern causes/effects ●similarly, it is difficult to pinpoint the specific effect of fishing