Population Ecology IV 2011

Population Ecology IV 2011 - ISHING MORTALITY IS REDUCED BY...

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Females, males and young segregate by water depth and distance to shore Mature at age 15 and live to about 30 Females gestate for 9 to 12 months, and have 8 to 9 pups in a year -- have ‘rest’ years in between reproductive years Give birth to live young (neonates) -- stay in nursery grounds for 1 year -- shallow bays and estuaries along east coast including Delaware Bay Juveniles migrate by season going to warmer waters near the Gulf Stream in winter and back to nursery grounds in summer Sub-adults do not breed but migrate with adults along East Coast -- as far north as New England in summer and south in winter
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1.00 1.05 1.10 0.95 0.90 0.85 0.80 0.00 0.05 0.10 0.15 0.20 0.25 Rate of population change (R) Rate of Fshing mortality (±) Relationship between rate of increase (R) and Fshing mortality (±). F critical is reached at 0.071. If F is less than F critical the population will increase, and if it is greater than F critical the population will decrease.
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Unformatted text preview: ISHING MORTALITY IS REDUCED BY SETTING LIMITS. CURRENT LIMITS ARE = 0.20, SET IN 1996 IN RESPONSE TO OBSERVED POPULAITON DECLINE. 0.071 << 0.20 Yikes! Further Management Options: (1) Reduce fshing mortality overall (current conditions) (2) Protect nursery grounds when emales give birth only (3) Protect nursery grounds all summer (4) Set size limits or harvest so juveniles are not killed (5) Set size limits so subadults are not killed ALL OPTIONS MUST INCLUDE REDUCTIONS IN FISHING MORTALITY TO MAKE THE POPULATION STABLE Fig. 2. Instantaneous rates of change in relative abundance (95% confidence intervals) for (A) great sharks and (B) elasmobranch mesopredators, as estimated by random-effects meta-analyses of research survey ( ) and fisheries ( ) data. R A Myers et al. Science 2007;315:1846-1850 Published by AAAS Rate of population increase (R) 1.0 +...
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This note was uploaded on 08/18/2011 for the course ECOLOGY 351 taught by Professor Staff during the Spring '11 term at Rutgers.

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Population Ecology IV 2011 - ISHING MORTALITY IS REDUCED BY...

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