Chapter 13: Wildlife, Fisheries and Endangered Species

Overview Traditional Single-Species Wildlife Management Improved Approaches to Wildlife Management Fisheries Endangered Species: Current Status How a Species Becomes Endangered and Extinct The Good News: We Have Improved Some Species Can A Species Be Too Abundant? How People Cause Extinction and Affect Biological Diversity Ecological Islands and Biodiversity Using Spatial Relationships to Conserve Endangered Species

Single-Species Wildlife Management Each species viewed as a single population in isolation Assumptions: Population only represented by a single number- total size Population would grow to its carrying capacity Environment, except for human-induced changes, is constant

Single-Species Wildlife Management This perception illustrated by the S-shaped logistic growth equation Two management goals resulted: For a species we intend to harvest: maximum sustainable yield (MSY) For a species we intend to conserve: keep population at its carrying capacity

Single-Species Wildlife Management This approach failed because none of the assumptions were accurate Population cannot be represented only by a single number Population does not remain at a fixed carrying capacity The environment is not constant

Single-Species Wildlife Management 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

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”

Logistic Growth Curve Using this growth curve: The number 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 number Therefore, all individuals are equal The environment can be assumed to be constant

Carrying Capacity Three definitions Logistical carrying capacity- Number of individuals is just sufficient for the available resources An abundance at which a population can sustain itself without any detrimental effects that would decrease the ability of that species to maintain that abundance Optimum sustainable population- Maximum population that can be sustained indefinitely

Logistic Growth Curve Maximum sustainable yield (MSY) Exactly one-half of the carrying capacity Other estimating MSY will lead to overharvesting

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 w/ the entire community of organisms and all the renewable resources

Improved Approaches to Wildlife Management Maintenance of the ecosystem of which the wildlife are a part Continual monitoring, analysis, and assessment

Time Series and Historical Range of Variation Set of estimates over a number of years Historical range variation Known range of abundance of a population of species over some past time interval Ex: American whooping crane

Age Structure as Useful Information Additional key to successful wildlife management Ex: Salmon from the Columbia River, WA Shift in catch towards younger ages 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 Number harvested- method of estimating animal populations Previous animal abundance can be estimated by catch per unit effort Assumes same effort by all hunters/fisherman per unit time If total time spent hunting and catch per unit effort is known, population can be estimated Ex: Bowhead whale

Fisheries Fish are an important food source Continental shelves 16% of the world’s protein 6.6% of food in North America Continental shelves Only 10% of ocean area Provide 90% of fish harvest Areas of high algae production to support food chain Upwelling

Fisheries World fish harvest has increased greatly since the middle of the 20th century Increased number of boats Improved in technology Increase 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 Ex: 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 Ex: Atlantic salmon fisheries cause water pollution and loss of genetic diversity

Endangered Species: Current Status Number 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

Endangered Species: Current Status The term endangered species as defined by the Endangered Species Act “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 1800s, ~1 species per year went extinct Rate of evolution of new species = or > the rate of extinction Average longevity of a species 10 million years Other periods of “punctuated extinctions”

Causes of Extinction Population Risk Environmental Risk Problem for species in low abundance Environmental Risk Variation in physical or biological environment Natural Catastrophe Sudden change in the environment Genetic Risk Reduction in genetic variation

The Good News… Thanks to people, many previously endangered species have recovered Aleutian goose Elephant seal Sea otter Blue whale Bald eagle Osprey

Can a Species Be Too Abundant? Protected animals can become locally overabundant Sea lions in San Francisco Harbors Sun themselves on boat Pollute water with feces Mountain lions in CA People living in lion hunting grounds More frequent human attacks

How People Cause Extinctions and Affect Biological Diversity Hunting or harvesting Disrupting or eliminating habitats Introducing exotic species Creating pollution 75% of Extinctions since the 1600s have been caused by humans

Ecological Islands and Endangered Species Areas that are biologically isolated Examples: islands, Small city parks (ex: Central Park in NYC) and large nature preserves are both isolated

Ecological Islands and Endangered Species How large must an ecological island be to ensure survival of a species? Depends on species requirements

Using Spatial Relationships to Conserve Endangered Species Red-cockaded woodpecker An endangered species Nests in old dead or dying pines Feeds on pine bark beetle which are a pest to the tree

Using Spatial Relationships to Conserve Endangered Species A new approach to conservation Overlay a map of one’s habitat requirements over a map of the other’s Co-occurrence can be compared and allow maintenance of all three specie