Potential drivers and consequences of cod recovery in the northwest Atlantic
Download 3.64 Kb.
|
| Potential drivers and consequences of cod recovery in the northwest Atlantic
Graham D Sherwood, Gulf of Maine Research Institute, 350 Commercial St., Portland ME 04101 Cod (Gadus morhua) stocks throughout much of the north Atlantic underwent dramatic declines in the late eighties to mid nineties and many remain at historically low biomass levels. In a recent paper on stock recovery potential for various cod stocks on both sides of the Atlantic (Hilborn & Litzinger 2009), it was argued that most stocks (13 out of 18 examined) would recover fully in the absence of fishing with the exception of 5 Canadian stocks which, even under fishing bans, show no net productivity. Environmental drivers were invoked but not elaborated any further. In this talk, I will first review evidence for a food-web shift in Newfoundland and Labrador (NL) that may have exacerbated overfishing contributing to stock collapse and subsequent poor recovery. In particular, capelin, a dominant forage species in north-temperate continental shelf ecosystems, declined concurrently with cod stocks in NL and has yet to re-establish high numbers. This has been shown to negatively impact cod growth, condition and reproductive capacity. Next, while cod stocks in the Gulf of Maine (GOM) appear to be recovering, possibly as a result of increasingly more restrictive fishing rules, certain inshore areas (historical fishing and spawning grounds) are practically devoid of cod and forage fish shortages, in this case river herring, are suspected to be involved. Finally, the decline of cod and other large predators in the GOM and NL appears to have precipitated a shift to crustacean dominated fisheries (lobsters in the GOM and snow crab and shrimp in NL) with historically high landings values. It is unknown how rebuilt cod stocks will impact these species but ongoing research in the GOM suggests that lobster abundance and movement/foraging behavior can be limited by cod and other predators. Directory: biology biology -> Raising Awareness: Developing Social Media Campaigns About hiv and aids biology -> For Thursday Nov 13th Students will choose one side of this assignment page biology -> For Thursday Dec 9th Students will choose one side of this assignment page. The Adaptationist Program Discussion biology -> Discussion Questions regarding the Adaptationist Program biology -> Atypical Sexual Behavior Common Versus Atypical Sexual Behavior biology -> Data acquisition wcr 20131018 biology -> Island biogeography and evolution biology -> Study Guide for Chapter 30 Lab Exam biology -> Midterm 1: Answer Key biology -> - Download 3.64 Kb. Share with your friends:
|