Challenge 3 - Sustainable harvesting Flashcards
what is sustainable harvesting?
the largest amount of harvest activity that can occur without degrading the productivity of the stock
what are the 5 important points to note when thinking about sustainably harvesting?
>population size >precision of population estimate > rate of population increase > rate of harvesting >ethics
how do you measure population size?
> distribution
abundance
density
dispersion
what is distribution?
(where are things?)
> dimensionless
> important for conservation, disease
what are the types of dispersion?
> how clumped are the organisms?
clumped, random and uniform
what is abundance?
(how many things are there?)
> important for conservation, species management, disease.
> needed in conjunction with distribution
what is density?
> qualification of abundance taking into consideration dispersion
how do you estimate changes in population size? (formula)
future population size = current size + #births - #deaths
>ignoring any arrivals or departures from/to other population
what affects both births and deaths?
> demography
survivorship
life history strategies
what is demography?
age and sex structure will influence population growth of the next generation
what is survivorship?
> % chance of offspring getting to breeding age,
chances of survival can differ dramatically among different species,
some suffer most of their mortality early in life, others later
what is life histories
> description of when an organisms reproduces
how many offspring it makes
how much investment in offspring
how many times it reproduces
what are the what is the size number trade off?
you can either have less energy (small size) per offspring and make more offspring, or you can have more energy (large size) per offspring and have less offspring
what are two examples of animals with differing size-number ratios of offspring?
salmon = 1 million eggs, little investment per offspring kiwi = 1 egg, every bit of investment
what are the two different types of parental care?
semelparity vs iteroparity
what is semelparity?
semelparity is big investment either in quality or number of offspring (northern quoll)
what is iteroparity?
iteroparity is less of an investment per round but more rounds
what are some other factors that are important for generation time?
> offspring size / parental care
> age at reproduction/ generation time
what are the pros of being semelparous?
> doubts /low probability about making it to the next cycle
worthwhile breeding now while you can
increasing amount of offspring
what is rMAX?
the maximum population growth (constant)
describe exponential population growth
> it has a lag time for the first few generations
then the growth is exponential.
the formula is dN/dt = rmax x N (population size)
species that follow this type of growth curve are called r type species
bacteria, cane toads, flies
also called opportunistic species
describe logistic population growth
> small lag
exponential growth at first
deceleration
then a stable equilibrium
formula is dN/dt = rmax x N[(K-N)/N]
where k is the carrying capacity
K could be # of predators, # of resources
species that follow this curve are called k type species
also called equilibrial species
also has a point of maximum growth, which has the steepest gradient.
describe a thermal dependance curve
> has a critical thermal minimum (CTmin), i.e., the lowest temperature an animal an survive in
CT max
Topt (optimum temperature for fitness
Pmax (performance at Topt)
know the difference between a thermal dependance curve in a temperate environment and a tropical environment.
also know climate change will affect these distributions and the organisms that live in those bounds
what is an ecological niche?
> an organism’s “fit” to the environment
each organism relies on a unique mix of resources
each organism is compatible with a set of environmental conditions
what is a fundamental niche?
> the theoretical conditions a species can survive in
where they CAN live
factors include: temperature, salinity, moisture ranges
what is a realised niche?
> subset of fundamental niche
restrained because of species interactions
the environments where a species DOES live
competition with other species for resources determines realised niche.
what are the characteristics of an equilibrial species?
> stable environments > reproduce late > live for a long time > low mortality rate > iteroparous > high investment in a few offspring (not necessarily) > often extensive parental care > often follow K species curves
what are the characteristics of opportunistic species?
> hugely variable environment / many disturbances
reproduce early in life cycle
live fast, die young
high mortality rate
semelparous
low investment in each offspring but lots of offspring
little to no parental care
R species
these species are more suited to urbanisation.
lots of young that mature quickly then breed and reproduce quickly
what environments select for each type of life history (K and R)
> frequent environmental disturbance can select for opportunistic life histories
lawn mower = advantage for opportunistic life histories
what regulates intrinsic population growth?
Density dependent factors (negative) >competition >predation Density independent factors >climate > seasonal change in temp > carrying capacity
how does predation affect intrinsic growth rate?
> in the presence of different predators, tadpoles (and other animals) can express different phenotypes then each other and from a control
in tadpoles in the same enclosure as fish, they had a much smaller tail, letting then swim faster to escape death
in tadpoles in the same enclosure as beetles (that act in the same way as dragonfly larvae) they had a much larger tail, this is so that some of the flesh is expendable, and their vitals are protected.
how does competition affect intrinsic growth rate?
> resources are limited at a local scale
as density increase, ratio of consumer to resources increases
as density of population increases, growth rate decreases, as less food available.
also tadpoles can secrete growth inhibiting hormones to those round them.
in barnacles, higher competition meant that they were smaller and invested less resources into reproduction, so offspring smaller than in barnacles with less competition (gonad size)
