MAR 370: Exam 2 Review

Tiger sharks & bottlenose dolphins in Shark Bay, Australia
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Tiger sharks & bottlenose dolphins in Shark Bay, Australia
- Prey biomass of bottlenose dolphins is always higher in shallow habitats

- Tiger sharks are common only in warmer periods and prefer shallow habitats

- Foraging dolphins adjust their preference for foraging habitat to minimize their risk of predation
How can whales act as providers for an ecosystem?
- Humpbacks may provide significant energy into oligotrophic systems during winter months.

- Combination of carcasses, placentas and sloughed skin.

Carcasses: Up to 150-1,750 metric tons of biomass each year.

Placentas: Up to 19 metric tons of biomass each year.
Whale Pump Hypothesis
Whales carry nutrients, especially nitrogen, from the depths where they feed back to the surface via their feces. This waste strongly enhances productivity of fisheries, scientists have found. They've called their discovery a "whale pump," reversing the assumption that whales accelerate loss of nutrients to the bottom.
Seals & Northern Cod
Scenario 1: Seals eat commercially important fish.
-There are more fish if there are less seals.

Scenario 2: Seals eat predators of commercially important fish.
-There are more predators if there are less seals.

Scenario 3: The food web is more complicated than that.
-The effects of taking some number of seals out of the ecosystem are difficult to predetermine.
Top-Down Trophic Cascade
A trophic cascade where the top consumer/predator controls the primary consumer population.

The removal of the top predator can alter the food web dynamics.

In this case, the primary consumers would overpopulate and exploit the primary producers.
Bottom-Up Trophic Cascade
A trophic cascade where the primary producers will always control the increase/decrease of the energy in the higher trophic levels.

This food web relies on the availability and limitation of resources.

All populations will experience growth if there is initially a large amount of nutrients.

ex: El Niño causes coastal upwellings that bring cold, nutrient-rich water from below the thermocline up to the surface.
Keystone Species
A species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically.

ex: Sea Otters, Starfish
Critical Habitat
A habitat area essential to the conservation of a listed species, though the area need not actually be occupied by the species at the time it is designated.

ex: Steller Sea Lion critical habitat provides protection from potential competition for important prey species in waters adjacent to rookeries and important haulouts.
Population
A group of individuals/organisms of the same species occupying a particular space at a particular time.
Distribution
Size, shape and location of the area a population occupies, and the pattern of spacing within it.
DensityNumber of individuals per unit area.AbundanceTotal number of individuals, or biomass, of a species in a particular area.Basic Components of Population Biology- Abundance - Rate of change (+ or -) - Population structureMeans of studying population structurePhoto-ID: Use of natural markings, pigmentation patterns, shape of fins and flukes to identify individualsMonitoring populations of marine mammals- True census - Sampling estimates - Indices - Mark-recapture studiesLine transect surveys- Developed initially for terrestrial applications - Used extensively to study marine mammal populations (ecology, stock assessment) - Can be scaled according to specific question or goal - Can survey small areas to whole EEZsLine transect surveys - Assumptions- Animals are distributed throughout an area according to some stochastic process - Track lines are placed randomly with respect to the local distribution of animals - Objects on track line are always detected - Objects are detected at initial location, prior to response to observer - Distances are measured accuratelyMark-recapture techniques1. "Mark" animals (initial survey effort using photo-ID techniques) 2. Allow marked animals to redistribute among non-marked animals 3. "Recapture" animals (second survey effort using photo-ID) 4. Determine population size using the proportion of marked animals (R/S) = (M/N) - R = animals recaptured - S = sample size - M = animals marked - N = population sizePopulation size equation∆ N = (B-D) + (I -E) B = births D = deaths I = immigration E = emigrationDensity dependenceAs population nears carrying capacity, we expect: - Increase in juvenile mortality - Increase in age at sexual maturation - Decrease in fecundity - Increase in adult mortalityPopulation biology of pinnipeds- High fecundity - Moderate rates of survival - High dispersal ability - Thus, relatively high potential rates of increase - MMPA default value of 12% per yearPopulation biology of cetaceans- Low fecundity - High rates of survival - Low dispersal ability - Thus, relatively low potential rates of increase - MMPA default value of 4% per yearLife History TheoryHow animals should allocate time and energy in order to maximize fitnessPrinciple Life History Traits- Size at birth - Patterns of growth - Age at sexual maturity - Size at maturity - Reproductive schedule - Number and sex of offspring - LifespanLife History Constraints- Single offspring per pregnancy - Long juvenile period of physical and social development - Terrestrial parturition (pinnipeds)Methods of studying life history1. Cross-Sectional Approach - Directed specimen collection - Carcass salvage - Commercial or aboriginal hunts - Fisheries by-catch - Strandings 2. Longitudinal Approach - Following the lives of individual animals - Photo-ID, tagging, marking, captures 3. Combined ApproachHow does body size affect gestation duration?Larger body size = longer gestational periodSelective advantages to a 12-month reproductive cycleMysticetes: annual migrations Pinnipeds: minimize number of trips to shoreBased on their body size...Mysticetes should have gestation periods of > 12 months Pinnipeds should have gestation periods of < 12 months But they don't --> WHY? Elevated fetal growth rates shortens gestation duration in mysticetes Embryonic diapause lengthens gestation duration in pinnipedsLife history characteristics of pinnipeds- Terrestrial parturition - Post-partum estrus - Embryonic diapauseLife history characteristics of mysticetes- Extensive seasonal migrations - Seasonal reproduction - Large body size - Females larger than males - Relatively short period of parental careWhy do baleen whales migrate?A. Possible Benefits to Adults - Thermoregulation in warm water during winter - Evolutionary tradition & continental drift - Tracking resources B. Possible Benefits to Calves - Thermoregulation in warm water after birth - Calm water after birth - Reduced risk of predation from killer whalesLife history characteristics of odontocetes- Resident or weakly migratory - Seasonal reproduction in high-latitude species - Great variation in size and dimorphism In some species (sperm, killer, & pilot whales): - Long periods of maternal investment - Extended life spans - Reproductive senescenceDolphin vs. Porpoise life historyDolphins: - "Slow" life histories - Larger size - Long birth interval (2-7 yrs) - High age of first reproduction (5-17 yrs) - Long reproductive life Porpoises: - Smaller size - Annual birth interval - Early age at first reproduction (2-4 yrs) - Short reproductive lifeReproductive senescence*Extremely rare in mammals* Functions of menopause: - No adaptive significance - (1) Stop early hypothesis - (2) Grandmother effectReproductive strategies- Central to ability to maximize fitness - Animals behave so as to maximize their reproductive success over their lifetime - Differences in male and female investmentsFitnessThe ability of an organism to produce viable offspring capable of surviving to the next generationEnergetic costs of reproductionFor Females: - Gestation (producing fetus) [LESS DEMANDING] - Lactation (nursing until weaning) [MORE DEMANDING] For Males: - Gaining & maintaining access to femalesIncome BreedersDuring breeding, energy is converted directly from the dietCapital BreedersDuring breeding, energy is obtained from stored suppliesForaging cycle strategy - Otariids- Moderate maternal energy stores prior to birth - Alternating nursing bouts and feeding trips to sea - Long lactation period (4 months - 2 years) - Low milk fat (19 - 50%) - Slow pup growth - Small adult body size [INCOME BREEDING]Fasting strategy - Phocids- Large maternal energy stores prior to birth - Fast during lactation - Short lactation period (4 - 50 days) - High milk fat (40 - 60%) - Rapid pup growth - Large adult body size [CAPITAL BREEDING]Advantages of fasting while nursingAllows feeding in environments that are unsuitable for giving birth or nursing young Requires a large body size (increased storage ability) [PHOCIDS AND MYSTICETES]Cetaceans lactation strategiesMysticetes: - Separate periods of feeding & lactation - Females store energy during intensive feeding season - Relatively short lactation periods Odontocetes: - Nurse while feeding - Energy from food transferred directly into milk - Relatively long lactation periodsBiotelemetryGoal: Remotely measure information about an animal Why is this important? - Observer effects - Marine mammals don't spend much time around scientistsTagsInstruments that are: - Placed on (or in) an animal - Either temporarily or permanently - Record (archival) and/or transmit (telemeter) dataData Types- Individual identity - Location (range of temporal/spatial resolutions) - Animal physiology (heart rate, temperature) - Animal movement (depth, acceleration) - Environmental ConditionsHow to tell one seal from another?- Natural "tags": coloration, spot patterns, scars, etc. - Markings: "branding" - Genetics: requires sample (biopsy, feces) - Flipper tags: invasive, permanentHow to tell where a seal is?- ID tags: sight, resight - Telemetry: VEMCO "pinger" tags, require receiver network - Satellite tags: can approximate latitude / longitude; requires out of water sensorLimitations of a tag- Cost and complexity - Tag size (relative to animal, # of sensors, battery) - Impact on animal (drag, change in behavior, fitness reduction, predator attraction, injury/death)Passive AcousticsListening to the environment Advantages: - Easy to remotely monitor areas - High temporal resolution (seconds to minutes) - Long time-series (months to years) Challenges: - Identification of sound sources -> animal + behaviorMarine Mammal Protection Act (MMPA)Passed in 1972 in response to public concern over: - Over-exploitation of baleen whales - Mortality of dolphins in ETP purse seine fishery - Canadian harvest of harp seal pupsFundamental objectives of MMPA1. To maintain stocks of marine mammals at their optimum sustainable populations (OSP) 2. To maintain marine mammal stocks as functioning elements of their ecosystemsSplit Jurisdiction for MMPANational Marine Fisheries Service (Department of Commerce): Whales, Dolphins & Porpoises, Seals & Sea Lions U.S. Fish & Wildlife Service (Department of Interior): Manatees, Polar Bears, Sea Otters, WalrusBreakdown of MMPATitle I - Conservation and Protection of Marine Mammals Title II - Marine Mammal Commission Title III - International Dolphin Conservation Program Title IV - Marine Mammal Health & Stranding ResponseTitle I of MMPAProhibits taking of all marine mammals Take means to: harass, hunt, capture or kill Exceptions: Scientific research, Public display, Subsistence harvest, Commercial fisheries (under certain conditions), Industrial & military activitiesTitle II of MMPAEstablishes the Marine Mammal Commission - Independent body to overview implementation of the MMPA - Advises Congress on actions required to implement the Act - Recommendations made available to the public (Annual Report to Congress)Title III of MMPAInternational Dolphin Conservation Program - Addresses interactions between pelagic dolphins and the Eastern Tropical Pacific yellowfin tuna purse seine fishery - Establishes limits on dolphin mortality in this fishery - Specifies requirements for observers and research programs - Establishes limitations on importation of tuna harvested by fisheries of other nationsTitle IV of MMPAMarine Mammal Health & Safety Response - Facilitate collection of reference data on the health of wild marine mammals - Establishes procedures for rescuing and rehabilitating stranded marine mammals - Establishes procedures and practices for stranding network participants - Co-ordinates effective responses to unusual mortality eventsMMPA Reauthorizations1988: - Provided an interim exemption to commercial fisheries - Allowed NMFS/FWS time to conduct stock assessments 1994: - Established a new regime governing interactions with commercial fisheries (Section 118)Potential Biological RemovalPBR = (Nmin) × (½ rmax) × (Fr) Nmin = minimum population estimate rmax = maximum rate of increase Fr = recovery factor *If anthropogenic mortality > PBR, stock is considered strategicSuccesses of the MMPA- Recovery of many depleted populations (especially pinnipeds) - Improved knowledge of marine mammal population biology - Protection of individual marine mammals from harmFailures of the MMPA- Health and stability of marine ecosystems not addressed - Lack of recovery of some endangered species - Unexplained decline of some populations - Treats all individuals are equal in populations - social structure ignored - Not been very effective in addressing indirect impacts (e.g., anthropogenic sound, disease, prey depletion) - Failures in implementation, enforcementEndangered Species Act (ESA)Passed in 1973 in response to animals being affected by: - Destruction of habitat - Overexploitation - Disease or predation - Inadequate regulatory protection - Other factorsExtinct Marine Mammal Species- Steller's Sea Cow (since 1768) - Sea Mink (since 1880) - Caribbean Monk Seal (since 1952) - Japanese Sea Lion (since the 1970s) - Baiji (since 2006)Critically Endangered Marine Mammal Species- Vaquita - North Atlantic Right Whale - Mediterranean Monk SealESA CategoriesEndangered: "any species which is in danger of extinction throughout all or part of its range" - e.g. Hawaiian monk seal Threatened: "any species which is likely to become an endangered species within the foreseeable future" - e.g. bearded sealFundamental objectives of ESA- Provide a means whereby ecosystems of threatened and endangered species may be conserved - Provide a program for the conservation of threatened and endangered species - Take steps to achieve purposes of relevant treaties and conventionsWhat is considered a species under the ESA?A species includes any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature ex: Southern resident killer whalesDomestic marine mammal species listed under the ESAThreatened: - California sea otter - Eastern Steller's sea lion - SW Alaskan sea otter - Ringed seal - Bearded Seal - Guadalupe Fur Seal - Ringed Seal - Humpback whale (Mexico Distinct Population Segments (DPS)) Endangered: - Blue whale - Fin whale - Humpback whale (4 DPSs) - Sei whale - Right whale (N. Atlantic & N. Pacific) - Bowhead whale - Rice's whale - Sperm whale - Cook Inlet beluga - Florida manatee - Western DPS Steller's sea lion - Hawaiian monk seal - False killer whale - Southern resident DPS killer whaleWhat is unique about the ESA?Habitat is included! - A take includes any habitat modification that kills or injures wildlife - Sections 3 & 4 require the federal government to designate "critical habitat" for endangered and threatened species - Section 5 authorizes the federal government to acquire land for habitat protectionRecovery Plans- Section 4 of ESA directs the USFWS or NMFS to develop and implement a Recovery Plan, unless such a plan will not promote the conservation of a species. - Plans should identify specific tasks necessary to recover a species to a stage where it can be downlisted or delisted - Developed by species experts, interested agencies, organizations, and individuals with public review and commentStock trends in marine mammalsSmall cetaceans have the most stocks overall in the US, but the lowest proportion of endangered stocks Large cetaceans have the highest proportion of endangered stocksProblems with the ESA- Many species listed too late - Listing & delisting criteria poorly defined - Focus on single, high profile, charismatic species - Critical habitat rarely designated or protected - Insufficient funding available to achieve recoverySuccesses of the ESA- Extinction of many species prevented - Evaluation of threats by federal government - Delisting & down-listing of more than 20 speciesFailures of the ESA- Protection for species (or populations) not ecosystems - Difficulties in down-listing or delisting species - U.S. solution to a global issue