BSC 3052 Conservation Biology Weeks 10 and 11 Study Questions 21 through 28 March 1 Suppose you are still studying an endangered fish with two life stages You examine your lab notebook to remind yourself that you collected data on this species as follows You tagged 250 juveniles and 120 adults in the wild The next year 64 of the juveniles had become adults and 31 were still juveniles The rest were nowhere to be found and you presumed they died You also recaptured 97 of your tagged adults Use these data as appropriate to determine values for per capita survival of juveniles and adults SJ and SA respectively and growth or maturation of juveniles to adults G given that they survive Express these values in terms of fractions rather than decimals What are the rates of juvenile and adult mortality in this species Mark 250 juveniles 64 became adults 31 remained juveniles o Therefore 64 31 95 survived o And 250 95 155 assumed dead Mark 120 adults Recapture 97 adults So 23 assumed dead Principal of probability to remember probabilities add up to 1 Juvenile can survive OR it cannot survive Therefore the mortality rate is 1 survival rate Survival rate Mortality rate 1 95 250 155 250 1 Survival of juveniles doesn t care what fate is as long as they still survived Sj 64 31 250 95 250 Mortality of juveniles Mj 155 250 or 1 Sj 1 95 250 155 250 Growth of juvenile to adult given that it survived Gj number of juveniles that became adults total survived 64 95 Probability of staying a juvenile given that it survived Jj number of juveniles that remained juveniles total survived 31 95 Or 1 Gj 1 64 95 31 95 Survival of adults Sa 97 120 Mortality of adults Ma 23 120 Or 1 Sa 1 97 120 23 120 The probability of two independent events is the product of their individual probability Probability of juveniles that matured to adults Sj x Gj 95 250 x 64 95 32 125 Probability of juveniles that remained juveniles Sj x Jj 95 250 x 31 95 31 250 Probability of adults that remained adults Sa Number of adults that survived total number of adults 97 120 Another way to see this Gj Jj Sj Gj Sj Jj Sj Sa 2 Express the contributions of juveniles to juveniles and to adults and the contribution of adults to adults such as would be necessary to parameterize a stage structured population model see Study Question 2 for 19 March in terms of the rates you calculated in Question 1 For this question please express these rates in terms of letters not numbers Contribution of juveniles to juveniles and to adults J t 1 Sj Jt Ga Jt Contribution of adults to adults A t 1 Sj x Gj Jt Sa At Where J t 1 is the number of juveniles at time t 1 Sj survival of juveniles Ga growth of juveniles to adults Jt number of juveniles at time t A t 1 number of adults at time t 1 Sa survival of adults At number of adults at time t Using the matrix model to understand turtle dynamics Sources of turtle mortality Beaches nestlings Ocean juveniles adults What if we protect turtles on the beach protect nestlings Change nestling survival to 100 What happens to lambda 974 What happens if we protect large juveniles in the ocean Use TEDs Decrease large juvenile mortality by 25 1 006 3 Why was the reasoning you went through for Question 2 important to understand the population dynamic effects of conservation alternatives for loggerhead sea turtles What was the primary conservation lesson to emerge from this analysis of stage structured models for loggerheads Briefly describe the conservation action that was implemented largely as a result of these analyses and briefly explain why it is not very easy to know whether or not this action is improving the turtle s population status Changed parameters Better to protect the juveniles and adults in the ocean larger lambda slope Protect larger juvenile and midsize adults we can really protect the population Which stage class do we need to protect How to keep survivability high Hard to know if this is working hard to enforce intentionally throwing them in so it doesn t work Don t know for sure how they are doing but we do know that is the right parameter to protect Protecting them in the ocean Big risk factor was the nets catching the turtles TED Turtle excluder device allowed turtle to get freed from net Turtles don t line up for consensus Conservation outcome 1987 TEDs required offshore May August 1988 89 Court challenges delay 1990 TEDs implemented seasonally 1993 year round TEDs offshore 1994 year round and inshore TEDs Models predict 40 50 years of transient dynamics In summary linear structured models Include information about age stage size structure Are amenable to empirical data Easily yield asymptotic population growth rate stable structure and sensitivity elasticity information And therefore enable targeting of stages with most influence on population increase for conservation or research focus But matrix models May divide a biological continuum into bins Can yield quite different dynamics if any matrix elements change subtantially and other such subtleties In the basic form we ve discussed do not explicitly include species interactions population limits random events Weeks 12 and 13 Study Questions 2 through 11 April 1 Provide two different definitions of population viability analysis What different aspects of population processes are emphasized by each What four questions about population dynamics are frequently addressed by any PVA however defined Define minimum viable population Definitions 1 Population viability analysis is the quantitative assessment of the probability that a population will become extinct within a specified time frame Old school definition emphasizes prediction 2 Population viability analysis is the estimation of extinction probabilities by analyses that incorporate identifiable threats to population survival into models of the extinction process More inclusive emphasizes analysis of threat should also emphasize biological mechanism Emphasizes prediction less Goes onto say why are you doing these analyses Doing it to analyze identifiable threats How are you doing it By a model Emphasizes analyses of threat over prediction shifts emphasis to biological mechanisms that threaten the pop and how they affect the probability of existence sometime in the future Questions Is the population declining What is the likelihood of extinction within x years o Likelihood probability o Has to do with underlying randomness o None of the models we have studied so far have to do with randomness What factors