Dec 01 2009

Dec 01 2009 - D. M. McComb, T. C. Tricas, and S. M. Kajiura...

Info iconThis preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon
D. M. McComb, T. C. Tricas, and S. M. Kajiura Enhanced visual fields in hammerhead sharks J. Exp. Biol. 2009 212: 4010-4018.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
BIEB132 December 1, 2009 Human Impacts: Fisheries Required reading: Levinton, Chapter 18 Brief overview of world ±sheries - once thought to be essentially inexhaustible, modern technology and markets have pushed many ±sheries into serious decline. A. Major ±shing areas 1. Most productive areas are the continental shelves of the North Atlantic, the upwelling coast of western South America, and off Japan. 2. Deep water is less productive and harder to Fsh. 3. Major offshore Fsheries are tuna (and historically, whales) B. Major commercial species 1. ±ish a. Herrings sardines and anchovies - small pelagics feeding at low trophic levels. Greatest biomass, low value as human food. b. Cod and relatives - bottom dwelling, feed high in the food chain. cold water. c. Mackerels and tuna - temperate and tropical. Tunas- among the largest Fsh involved in commercial Fsheries and some can bring >$10,000/Fsh. d. ±latFsh - halibut, ²ounder - premier food Fsh. Bottom dwelling e. Sharks 2. Invertebrates a. Crustaceans - crab shrimp and lobster b. Mollusks - snails, abalone, clams, mussels, squid, octopus
Background image of page 2
C. Fishing methods 1. Hook and line: traditional, trolling, long-line -- extending many miles 2. Nets (gill nets, trawls, purse seine) 3. Traps (e.g., lobster pots) II. Fisheries Management A. Estimates of abundance 1. Fishery dependent and independent statistics 2. Stock/recruitment relationship 3. Assumes each species can be evaluated and managed separately B. Basic model for maximum sustainable yield - higher resource productivity below carrying capacity III. Ecological consequences of ±sheries A. Ecosystem changes 1. Changes in the food web a. Fishing down the food web (now targeting smaller species) b. Ecosystem changes may prevent recovery of some species (Georges Bank: original cod, ±ounder, and had- dock ²sh populations, have been replaced by shark and ray populations) c. Reduced stability. By removing large individuals, the number of year classes reproducing may be cut (from ²ve to two in sardines). Two bad years of recruitment can then devastate the population. 2. By-catch a. Most ²shing gear is somewhat indiscriminant (turtles, dolphins) b. Trawling for shrimp yields enormous wasted bycatch 3. Habitat degradation a. Trawling - in some areas, the largest bottom-dwelling animals and plants have been entirely lost or signi²cantly altered . b. Removal of ²lter feeding bivalves - water quality reduced by phytoplankton blooms since former herbivores have been removed
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Tokyo: Tsukiji Fish Market Oceans are the last large scale region of the planet where humans function as hunter-gathers
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 6
Note the number of trophic levels in different environments
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 8
Purse seining
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Trawling (can be on surface, mid-water, bottom)
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 12
from Castro and Huber, 7ed, McGraw-Hill
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 14
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/23/2010 for the course BIEB BIEB 132 taught by Professor Hastings during the Fall '09 term at UCSD.

Page1 / 62

Dec 01 2009 - D. M. McComb, T. C. Tricas, and S. M. Kajiura...

This preview shows document pages 1 - 14. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online