The Chesapeake Blues What Happened? Inference Can you figure out what happened? Complications with Estimation Blue Crab Population Chesapeake Blues Company 1. Scoop out crabs diagonally 2. Pour onto desk and count 3. Record in journal 4. Place counted crabs in bag. 5. Replace counted crabs with tagged crabs 2. Scoop out crabs 1.Mix up the bay 3. Pour onto desk and count 4. Record in journal 5. Count how many were tagged 6. Record in journal Sample# captured# taggedRatio (t/c) Trial (total) Sample# captured# taggedRatio (t/c) Trial (total) 2. Scoop out a second sample of crabs 1. Put the captured crabs back into bay and mix 3. Pour onto desk and count 4. Count how many were tagged 5. Record both numbers on chart Sample# captured# taggedRatio (t/c) Trial (total) 6. Repeat steps to get sample 3 How many Blue crabs are in your bay? What information have we collected that might help us figure it out? Lincoln-Peterson Method assumes this ratio will be true in every sample. Original Tagged Crab Population (x) Total Captured Total Tagged Recaptured Insert Your Data Here How many Blue Crabs do you think were in your part of the Bay? GroupEstimation Class Data What was the average population of blue crabs in our bay? Assumptions We Made All crabs had an equal and independent chance of being captured. There isnt a change in the original ratio of tagged to total. We did not increase the catchability of the tagged crabs. What Do The Scientists Need to Know? Reproductive history of population Mortality pattern of the species Effects of marking on behavior Seasonal patterns of activity/movement Biases in the capture One Equation Scientists Use With Only One Recapture