Wildlife, Fisheries, and Endangered Species • Common history of exploitation, management and conservation • When saving a species, what is it we really want to save? • 1. A wild creature in a wild habitat • 2. A wild creature in a managed habitat. • 3. A population in a zoo. • 4. Genetic material only. • Many reasons for wishing to save endangered species. • Policies and actions are in place
Single-Species Wildlife Management Approach • Conservation and management often viewed each species as a single population in isolation. • 1. The population could be represented by a single number, its total size. • 2. Undisturbed by human activities, a population would grow to a fixed size, called the “carrying capacity”. • 3. Environment, except for human-induced changes, is constant.
This perception illustrated by the S-shaped logistic growth equation. • Two goals resulted: • 1. For a species we intend to harvest: maximum sustainable yield (the size of a natural population at which it produces a maximum rate of increase, typically at half the carrying capacity.) • 2. For a species we intend to conserve: remain at its carrying capacity • This approach failed. • None of the assumptions were true. • Population cannot be represented only by a single number. • Do not remain at a fixed carrying capacity. • The environment is not constant.
Necessary to include an ecosystem and landscape context for conservation and management. • New goals: • For a species to be harvested: sustain a harvestable population in a sustainable ecosystem • For a species that is threatened or endangered: minimum viable population (smallest population size at which it can exist without facing extinction)
Logistic Growth Curve • Include the following ideas: • A population that is small in relation to its resources grows at a nearly exponential rate. • Competition among individuals in the population slows the growth rate. • The greater the # of individuals, the greater the competition and the slower the rate of growth. • Eventually, a point is reached, called the “logistic carrying capacity”. • At this level, the # of births in a unit time equals the number of deaths, and the population is constant. • A population can be described simply by its total #. • Therefore, all individuals are equal. • The environment is assumed to be constant.
Carrying Capacity • Has three definitions. • 1. Logistical carrying capacity- the # of individuals is just sufficient for the available resources. • 2. An abundance at which a population can sustain itself w/o any detrimental effects that would decrease the ability of that species to maintain that abundance. • 3. Optimum sustainable population- the maximum population that can be sustained indefinitely. • Another key concept is that the population size that provides the max sustainable yield • Exactly one-half of the carrying capacity. • Other estimating MSY will lead to overharvesting.
The Grizzly Bear • An endangered species • US Fish and Wildlife Service must meet the requirements of ESA (Endangered Species Act) • Became endangered as a result of hunting and habitat loss. • Removed because dangerous to humans and livestock
Restore to what? • Past abundance (this is unknown) • Also lack good estimates of present abundance • Estimates include 1,200 in contiguous states, 32,000 in Alaska and 25,000 in Canada • Based on Lewis and Clarks records (and a number of assumptions) • The # of grizzly bears in 1805 in the US was 12,000 • Another approach is to ask what the minimum viable population is.
The American Bison • Brought close to extinction for 2 reasons • Hunted to make coats that were fashionable in Europe. • Killed as part of a warfare against the Plains peoples.
Improved Approaches to Wildlife Management • Four principles of wildlife conservation • A safety factor in terms of population size, to allow for limitations of knowledge and the imperfections of procedures. • Concern with the entire community of organisms and all the renewable resources. • Maintenance of the ecosystem of which the wildlife are a part. • Continual monitoring, analysis, and assessment. • Principles broaden the scope from a narrow focus on a single species to inclusion of the ecological community and ecosystem.
Time Series and Historical Range of Variation • Time series- • set of estimates over a # of years. • Historical range variation- • the known range of abundance of a population of species over some past time interval • E.g. American whooping crane
Age Structure as Useful Information • An additional key to successful wildlife management. • E.g. salmon from the Columbia River, WA • Shift in catch towards younger ages, along with an overall decline in catch, suggests that the fish were being exploited to a point at which they were not reaching older ages. • Early sign of overexploitation
Harvests as an Estimate of Numbers • Another method of estimating animal populations is to use the # harvested. • Previous animal abundance can also be estimated by • Catch per unit effort • Assumes same effort by all per unit time (same tech) • So if you know the total time spent in hunting and catch per unit effort, you can estimate total population • E.g. bowhead whale
Fisheries • Fish are an important food source • 16% of the world’s protein • Continental shelves provide 90% of fish harvest • Areas of high algae production to support food chain • Upwelling
Fisheries • The world’s fish harvest has increased greatly since the middle of the 20th century • Increase in # of boats • Improvements in technology • Increases in aquaculture production
The Decline of Fish Populations • Evidence that fish populations were declining came from the catch per unit effort. • Suggests fishing depletes fish quickly • About 80% decline in 15 years • Commercial fisheries are mining a resource not sustaining it.
The Decline of Fish Populations • Chesapeake Bay • Famous for oysters and crabs • Breeding and spawning ground for many commercially valuable species • Food webs very complex • Also influenced by runoff, introductions, development, alteration in salinity
The Decline of Fish Populations • Crisis has arisen for one of the living resources most subjected to science-based management. • Management based on logistic growth curve • Fisheries subjected to the “tragedy of the commons”
The Decline of Fish Populations • Fishing gear can be destructive to habitat. • Ground-trawling equipment destroys the ocean floor • Long-line fishing kills sea turtles and other non-target surface animals • Large tuna nets have killed dolphins.
Can Fishing Ever be Sustainable? • Few wild biological resources can sustain a harvest at a level that meets even low requirements for a growing business. • We can turn to farming fish (aquaculture) • Important food source in China, growing worldwide • Can create environmental problems • E.g. Atlantic salmon fisheries cause water pollution and loss of genetic diversity
The Current Status of Endangered Species • The # of species listed as threatened or endangered increasing • IUCN maintains a list known as the Red List • 20% of all know mammals at risk • 31% of amphibians • 3% of fish • 12.5% of plants recently extinct or endangered
The Current Status of Endangered Species • The term endangered species as defined by the ESA • “Any species which is in danger of extinction throughout all or a significant portion of its range…” • With the exception of insect pests • The term threatened species • “Means any species which is likely to become an endangered species w/in the foreseeable future throughout all or a significant portion of its range.”
How a Species Becomes Endangered and Extinct • Local extinction • Occurs when a species disappears from a part of its range but persist elsewhere. • Global extinction • Means a species can no longer be found anywhere
How a Species Becomes Endangered and Extinct • Rate of extinctions has varied over geologic time • From 580 million years ago until industrial revolution about one species per year • Rate of evolution of new species =or > the rate of extinction • Average longevity of a species 10 million years • Other periods of “punctuated extinctions”
How People Cause Extinctions and Affect Biological Diversity • By hunting or harvesting. • By disrupting or eliminating habitats. • By introducing exotic species. • By creating pollution.
How People Cause Extinctions and Affect Biological Diversity • The IUCN estimates 75% of the extinction of birds and mammals since 1600 have been caused by humans. • Current extinction rate estimated to be 1,000 times greater than extinction rate in Pleistocene
Good News • Species whose status has improved • Elephant seal • Sea otter • Many bird species effects by DDT, including bald eagle, brown pelican, white pelican, osprey and peregrine falcon. • Blue whale • Gray whale
Can a Species be too Abundant? • Sea lions now number 50,000 and have become a problem in S.F. and S.B. Harbors • Mountain lions in California • Both mountain lion and human population growing • People building in lion habitat • Attacks more common
The Kirtland’s Warbler and Environmental Change • Many species are adapted to natural environmental change. • If change eliminated the species can become endangered • Kirkland’s warbler in Michigan • From 1951-1971 found to be declining • Nest in jack-pine woodlands that are between 6-12 years old