A comprehensive literature review and modeling effort have been conducted in order to determine which vital rates are most important to determining the growth and sustainability of marine mammal populations. Also addressed are the impacts of life-history, ecological, and genetic variation on vital rates and population sustainability and how much each vital parameter can change before a change in population trend would be expected. Additionally, the influence of ecological energetics and foraging strategies on vital rates and their limits of sustainable change are examined, and the nature of how an increase in sound in the marine environment might influence marine mammal behavior, and thus life functions, vital rates and population sustainability is explored.
An analysis of the elasticity and sensitivity of marine mammal population models suggests that:
1) Most whale populations appear to be most sensitive to changes in adult female survival and least sensitive to calf survival.
2) Most whale populations appear to be secondarily sensitive to changes in juvenile survival and growth.
3) Most whale populations, with the exception of North Atlantic right whales (Eubalaena glacialis), appear to be insensitive to changes in fecundity at any age.
4) Adult female whales may be sensitive to changes in foraging success that limit their ability to acquire sufficient body stores of energy to sustain gestation, parturition, and lactation.
5) These results are similar to those arising from studies of non-mammalian marine predators as well as terrestrial vertebrates with similar life history characteristics.
A risk assessment of the potential impacts of ocean noise on marine mammal populations based on modeling marine mammal populations suggests that:
1) Any increase in anthropogenic noise in the marine environment that reduces adult female survival, for whatever reason, is to be avoided,
2) It may be impossible to detect the impact of a change in a population vital rate on population growth because such a change may be less than the confidence interval around the estimates of the rate of growth of most marine mammal populations.
3) Sensitivity and elasticity analyses of marine mammal population models predict linear changes in marine mammal population growth rates caused by linear changes in vital rates, and do not indicate thresholds within which vital rates can change without altering population growth rates.
Future research efforts should focus on the following:
1) The relationship between noise in the marine environment and adult female and juvenile survival.
2) To increase the precision and decrease the uncertainty of marine mammal population and vital rate estimates.
3) Improving the concept of potential biological removal (PBR) to reflect cumulative mortality impacts and to incorporate the effects of noise.
4) Increasing knowledge of marine mammal activity budgets seasonally and in different parts of their habitats.
5) To more fully elucidate the roles of marine mammals in their ecosystems, and their importance as sentinels of ecosystem health.
6) To exhaustively utilize existing data and models because of the cost and difficulty of gathering more data.
E&P Sound & Marine Life Programme
Edward O. Keith. 2008. Critical Review of the Literature on Marine Mammal Population Modelling .E&P Sound & Marine Life Programme : 1 -63. http://nsuworks.nova.edu/occ_facreports/93.