7872 - Laserfiche WebLink

Home Browse Search

1 1 IBMSimulation Steps Each simulation started with a cohort of 10,000 dispersing larvae arriving in, or "colonizing" nursery habitat. Colonization occurred on either 1 June, 1 July, or 1 August. Initially all larvae were 9.0 mm TL which is the typical size of Colorado squawfish larvae entering backwaters, but were assigned different baseline growth rates (mm/day) randomly drawn from a normal distribution with a mean specified for each simulation and a coefficient of variation of 14.1 % (Bestgen 1996). For each larva each day, the number of attacks was determined using equations 4 and 5. For each attack, a predator size was drawn at random from that day's predator size distribution, and P(capture) was determined using equation 2. The probability that a larva would survive all attacks on a given day (P(survival)) was determined by multiplying together the individual probabilities of surviving each attack (i.e., 1-P(capture)) on that day. Whether or not the larva survived the day was determined by randomly drawing a number from a uniform distribution between 0 and 1; if the random number was less than or equal to the larva's probability of survival for the day, then it survived. Probability of survival was set to 1 for larvae > 25 mm because the capture equation and other observations showed that larvae of this size were no longer vulnerable to red shiner predation. At the end of a day, length of each surviving larva was increased based on the larva's initial baseline growth rate and that day's temperature using equation 1. This process was repeated for each larva each day, then the time step was incremented and surviving larvae were exposed to predation on the next day. Fish that survived to 25 mm or 1 October were considered to have recruited to the age-0 population in winter habitat. At the end 17