Module 2 Exam Flashcards
Commercial Fisheries
union of aquatic organisms and humans for consumptive purposes
treating aquatic organisms as an extractive resource
Extraction and sale of fish for consumptive purposes
Are commercial demands the reason aquaculture has been increasing?
Commercial demands may not necessarily be changing, aquaculture has been increasing because of lack of natural fish supply in the oceans and lakes (overfishing)
Bottom trawling
very large net dragged across ocean floor by boat
Float line above, chain below (“tickle chain”, encourages things on the bottom to get off of the bottom)
Mesh - smaller fish can sometimes escape; if back end begins to get packed with fish (can drag them for hours), many times small fish can’t even get to the mesh to be able to get out because it is so full of fish
Target species of bottom trawling, duration of trawls, and trawl speed
Target species - species on the bottom; pacific cod, rockfish, halibut, shrimp; possibility of getting fish other than target species
Duration of trawls: 3-5 hours, but up to 10-12 hours
Trawl speed - up to 1-7 knots, 4 knots is optimum
How do bottom trawlers cause habitat disturbance?
creating a lot of resistance on sea floor, leads to some environmental destruction
Suspension of sediments
Increase in water turbidity = blocks sunlight = reduces photosynthesis
Reduced habitat heterogeneity, less of that means less niches and places for small organisms to live
Resuspension of contaminants (e.g. PCBs)
Impacts on food web
Heterogeneity
nooks and crannies in habitat (creates more available niches)
Bycatch definition **
part of the capture that is discarded at sea, dead (or injured to an extent that death is result)
Capture = catch + bycatch + released alive
Target (discarded) and non target species
Reasons for discarding target species as bycatch **
wrong species, size, sex
fish are damaged
quota is reached
high grading
lack of space, chance of spoiling
Longline fishing
long line underwater attached to buoys to keep it close to the surface of the water; main line with smaller lines (snoods) coming off of it with baited hooks to catch fish
Hooks left in water, a lot of occupational hazards
Target species: swordfish, tuna, sablefish, pacific cod
Longline bycatch **
Bycatch is mostly pelagic, no crustaceans, must be able to be baited by hooks
Kills many sharks because they have to keep moving to stay alive and will die if stuck on hooks
Drift nets
free-floating gill net
25m to 50 km long
Target species: tuna, squid, pelagics
Can become detached and get left in the ocean (“ghost nets”), leads to many fish and other sea life getting entangled and killed
Drift net bycatch **
indiscriminate in the way entanglement can happen
Can catch whales, gets caught in the operculum of fish, can catch seabirds
Ghost nets can lead to a lot of lost bycatch
Impacts of commercial fishing on fish populations
Reduction in abundance of target and non-target species (overfishing)
Disturbance and loss of essential (critical) habitat (cascading effects on the population and/or individual level)
Impacts on rare or threatened species
Disruption of food web (using up target species, and could be taking up target species’ prey as non-target species, leaving target species less able to feed and reproduce)
Remobilization of contaminants
Fishing induced selection (causing artificial selection by taking larger, more successful, more fecund fish out of the water)
Recreational fisheries
where fishing is conducted by individuals for sport or leisure, with the possible secondary objective of catching fish for personal consumption
Compared to commercial, where more often conducted by groups of individuals who capture fish products for sale
Freshwater recreational fishing effort represents ______ of the global food fishing relative to all fishing effort
half
What is the difference between the location of recreational vs. commercial fishing?
There are many more recreational places to fish - freshwater as well as nearshore regions of oceans including estuaries, reefs, mangroves, and embayments; Often critical habitats of multiple life states (spawning, nursery, migratory) and recreational fishers often target immature individuals
Commercial uses more accessible locations (based on depth and economic profitability) that are often more distant from coastal regions or in larger inland bodies of water (e.g. Great Lakes)
Impacts of recreational fisheries
Catch the fish = no longer in the population = impact on the population/ecosystem
Direct harvest - for personal consumption
Discards and bycatch
Abandoned gear (fishing line, hooks, etc)
Accumulation of lead sinkers
Habitat disturbance - anchors, propeller scars, noise
Catch-and-release
Voluntary or mandated through regulations
Total bycatch estimates - 28% of total catch
Elements of angling event, can all have a physiological effect on a fish even if the fish lives - capture, handling, release
Why is angling duration during catch-and-release important? **
The physical exercise required to fight against being caught leads to an increase in lactic acid, muscle fatigue, increase in blood glucose, disruption of osmotic balance (Na, Cl, K; influences gill/cell functions), and chance of being predated while on the line (depredation)
Describe how blood lactate levels change during angling events **
Blood lactate levels increase at the beginning of angling because the fish is fighting back hard against being caught, but then plateaus because there’s only so much that can be maintained in the body before it causes muscle pain and fatigue
Capture - external tissue damage
Trauma to eyes, fins, mouth, skin
Feeding impairment, swimming impairment
Infection, compromised immune system
Capture - internal tissue damage (gut hooked)
Trauma to esophagus, gills, vital organs (can hook the heart)
Impaired physiology and function
Infection, compromised immune system
Barbed hooks (J hooks)
Barbed hooks get caught in the fish’s skin, making it harder for them to escape but also causing more tissue damage
Treble hook
more hooks to increase chance of getting a fish
Circle hook
made to prevent gut hooking - if fish swallows it, the hook gets pulled out of the guts without getting hooked, and then gets stuck in the corner of the mouth on the way out
How can handling cause damage to fish during catch-and-release?
Landing - touching with hand/net, slime removal, scale loss, damage to fish/gills
Hook removal - tissue trauma, especially with barbed hooks
Air exposure - to remove hook, take photo, transfer to live well; gills don’t work outside of water; after physical exertion from catching, being able to get oxygen is even more vital
Can lip gripping tools reduce the impacts of handling?
Bonefish held vertically in air, bonefish held horizontally in water, and control - ten bonefish in each group
Examined injury and mortality after 48 hrs
18/20 bonefish handled with boga grip suffered injuries - 100% of those held vertically and 80% of those held horizontally
40% of injuries were severe, likely resulting when bonefish thrashed
(tore through skin, broke jaw on some → bad outcome even if released due to feeding impairment and lack of defense against predators)
Impacts of air exposure **
Leads to collapse (no longer supported by water) and adhesion of gill filaments
Compromises respiration
Magnifies physiological disturbance - trying to recover from excessive exercise and now being forced to hold breath (can’t get oxygen in OR CO2 out)
Delays recovery - gill filaments have adhered and take a while to recover and begin working normally
Eventually leads to tissue damage and death
Acute impacts of catch-and-release
Slow physiological recovery
Impaired swimming performance - might not be able to swim against current or get away from predators
Altered behavior
Increased susceptibility to predation, especially in marine systems (more predators)
Loss of equilibrium - inability to coordinate movements and remain upright (good indicator of severe stress)
Fish without equilibrium were ____ times more likely to suffer predation
six
Factors that do NOT influence equilibrium
length of fish, incidence of bleeding, duration of fight
Factors that DO influence loss of equilibrium
duration of air exposure (for every minute of air exposure, chance of loss of equilibrium increases by 6 times)
handling time (for every minute of handling, chance of loss of equilibrium increases by 1.2 times)
Is mortality/survival alone an appropriate endpoint for assessing the complete effects of catch and release angling?
No, there is a lot of room between a dead fish and one that is a “fit” member of a population, catching also causes:
Physiological disturbances
Energetic consequences
Behavioral alterations
Fitness impairments
_____ water temperature causes _____ salmon mortality
higher, higher
Fish induced selection
Removal of large individuals from population
Selection favors slower growth rates and smaller body sizes (less susceptible to angling)
Fitness impairment – energy used to recover from angling cannot be spent on growth and reproduction
Individuals contribute less to the population
Habitat disturbances
loss or modification of essential habitat for each life stage
Ontogenetic shifts in habitat use
Disturbance or loss of any essential habitat could influence recruitment, growth, reproduction, and survival
Impacts on water quality could also be considered a disturbance of habitat – thermal pollution, nutrient enrichment (eutrophication)
What does “ontogenetic shifts in habitat use” mean?
habitat use changes with different life stages
ontogenetic = the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult
Water diversion
surface and ground water diverted from its natural course for anthropogenic (human) use
Irrigation of cropland, industrial use (hydro dams), domestic use (wells)
Dams and culverts
reduced flow, barrier to movement
Change in thermal regime
Change in sediment flow
Accumulation of contaminants (methylmercury)
Individual, population, and community-level effects
Diadromous fishes
migrate between freshwater and seawater environments
usually born in one type, move to another for growth, then move back to original type for spawning
Often very high site fidelity to natal streams/rivers
Anadromous fishes
born in freshwater, grow in marine (e.g. Atlantic salmon)
Catadromous fishes
born in marine, grow in freshwater (e.g. American eel)
What are the potential impacts of dams on populations of anadromous salmon? **
Can’t get out to the ocean to look for food and grow
Not able to return to freshwater to spawn
Riparian habitat
ecotone between terrestrial and aquatic ecosystems within a floodplain
Plants are adapted to being inundated with water
Acts as a buffer/filter
Land use practices often put pressure on riparian vegetation
Loss of riparian habitat
Disturbances - increase in sediment loads (increased phosphorus, as phosphorus abundant in ground), availability of habitat (less woody debris), nutrient enrichment, change in temperature regime (less shading)
Siltation of critical habitat (nesting grounds), reduced habitat heterogeneity, thermal stress, eutrophication
Impacts of forestry practices on riparian habitats
Plants in riparian zones filter out sediments and take up nitrates, so if trees are clear-cut there are more suspended sediments and nitrates
How can an increase in nutrient loads following the removal of riparian vegetation influence the life history of fish? **
Larval fish - increase in nutrient load could drive oxygen levels down, larval fish have high oxygen demand, so increased mortality
Juvenile fish - if oxygen is reduced it could impact growth/maturing of the fish, especially if the amount of available food is impacted
Adult fish - if oxygen is reduced it could impact the ability of the fish to reproduce, especially if the amount of available food is impacted
Increase nutrients could have positive effects, such as boosting the food web and increasing growth rates because there is more food available to fish
Structural complexity
The three-dimensional (3D) physical structure of an ecosystem, plays a critical role in mediating the dynamics of biological communities
Mosaic of habitat types (ex: coral reef ecosystems)
Food and shelter for inshore species
Biodiversity of the coastal zone
What do you think ‘connectivity’ means in the context of habitat use and fish movements? **
Some fish move habitats depending on their life stage because some biomes are better for growth, while others are better for spawning
If a fish has to move between one habitat and another, movement takes energy, which requires food
In a new environment there are also new predators
Water pollution
The contamination of water bodies such as streams, lakes, rivers, oceans, wetlands, and groundwater
Naturally occurring or human-generated compounds or conditions that can or will have a negative impact on any aspect of aquatic ecosystems
Direct or indirect impacts (individual fish versus cascading effects through the food web)
Point source (PS) pollutants **
Single identifiable localized source of pollution
Factories, sewage
Easy to calculate loading because pollution is coming from an isolated point
Non-point source (NPS) pollutants **
From diffuse sources
Runoff, rain, snowmelt
Difficult to calculate loading because anything could be picked up
Organic pollutants
Molecule contains carbon
From animals/plants, industry
Natural (methane), synthetic (PVC, plastics)
Inorganic pollutants
Mineral origin (e.g. Hg)
Manufacturing, industry, mining
Heavy metals, silt, fertilizer, acids
Persistent contaminants **
can be organic or inorganic
Resistant to environmental degradation - can’t be broken down over time (or at least it is very difficult for them to be broken down)
Low water solubility (hydrophobic)
High lipid solubility (lipophilic)
High capacity for long-range transport, potential for considerable impacts on biota
Persistent organic pollutants (POPs)
PCBs
Heavy metals (Hg)
Organometallics - methylmercury [CH3Hg]+
PFAS
Forever chemicals
per- and polyfluorinated alkyl substances
Why is it important that persistent contaminants have low water solubility (hydrophobic) and high lipid solubility (lipophilic)?
Persistent contaminants can stick around for a long time in lipid sources (such as in fish and other organisms because they contain a lot of lipids)
Because they don’t like water, they don’t get flushed out either
Bioaccumulation **
rate of accumulation is greater than the rate of loss/breakdown
Lipophilic compounds (organic), chronic effects of toxins
Because it binds to fats, it doesn’t break down easily and therefore sticks in animals for a long time
Increase in concentration within an organism; occurs within a trophic level
Biomagnification **
increase in concentration of a persistent contaminant that occurs across trophic levels (up food chain)
Contaminants stick in fats of fish, other animals eat those fish and accumulate a greater amount of contaminant, so when another organism eats that animal it accumulates even more contaminant
Mercury
Elemental Hg – naturally occurring but anthropogenic concentrations occur via waste incineration, coal burning, chlorine production, and ore extraction (e.g. gold mining)
Mostly atmospheric – returns to earth in rain or snow
Methylmercury – sulfate-reducing bacteria absorb and convert elemental Hg (inorganic) to this highly toxic, bioavailable form
Bioaccumulates and biomagnifies (lipophilic and hydrophobic)
Effects of mercury on fish
Acute exposure - elevated metabolic rates related to damage of gill epithelium (affects oxygen uptake, ion regulation)
Chronic exposure – impaired feeding ability, manifested as reduced foraging efficiency and capture speed
Dietary ingestion – severe liver damage, reduced fecundity, impaired gonadal function, reduced sperm motility, altered sex ratio
Effects of mercury up the food chain
Fish as prey for fish-eating birds (loons, eagles) and mammals (otters, mink, pinnipeds), and these animals are impacted through reproductive impairment and even mortality
Human health consequences – severe neurological damage, kidney damage
Cognitive impairment, muscle and joint pain, hair loss, increased coronary heart disease
Endocrine disrupting compounds (EDCs) **
Mimic the chemical activity of hormones or stimulate hormone production
Reproductive (estrogens, androgens), thyroid, and corticosteroid hormones
At least 90 chemicals found in food, water, soil, and air are EDCs
Oral contraceptives and diethylstilbestrol (synthetic estrogen), organohalogens (dioxins, PCBs), food antioxidants (BHA), pesticides (DDT, malathion), phthalates (plasticizers, printer ink, adhesives)
Function of hormones
A chemical released by one or more cells that affects cells in other parts of the organism
Often transported in blood (endocrine) or duct (exocrine), bind to hormone-specific cell receptors (protein), resulting in activation and cell response
Growth hormones (thyroid-stimulating hormone), hunger hormones (ghrelin), reproductive hormones (testosterone)
Balance of positive and negative feedback cycles -> balance is thrown off by pollution = does wacky things to fish and people
Individual-level effects of EDCs **
Reduced rates of sperm and egg production
Reduced gamete quality
Abnormal gonad morphology
Altered reproductive behavior
Altered embryonic development
Reduced reproductive success
Population-level effects of EDCs **
Decrease rates of survival, growth, reproductive capacity
Decreased population size
Risk of population extinction
Ecosystem-level effects of EDCs **
Disruption of food web
Loss of ecologically and economically important species
Human health concerns
Acid deposition
addition of acidic compounds from the atmosphere
Sulfuric (H2SO4), Nitric (HNO3), Nitrous (HNO2)
Industrial operations (factories, power plants, smelters), combustion engines (burning of fossil fuels), wood smoke
Wet deposition (rain, snow, fog), dry deposition (soot, ash)
Remember 1st lecture on water – ideal solvent and easily combines with acids
Leeches compounds out of soils at low pH - Al, Mg (water has limited buffering capacity because of low Ca)
Impacts of acid deposition on fish
Mobilization of aluminum (Al) increases as pH decreases
Al increases mucus production, including on gills
Reduced efficiency of oxygen uptake
Interferes with oxygen absorption by hemoglobin
Impaired regulation of ions in blood and tissues
Gill cell necrosis (death)
Reduced survival of eggs and larvae
Invasive species
nonnative, nonindigenous, introduced, alien, exotic, transplanted, translocated, feral, biological pollutant
Nonindigenous species (NIS)
one that has been moved beyond its natural range or natural zone of potential dispersal
Recognizes natural processes (dispersal, range extensions) as natural events, and focuses on movements that are human-induced and independent of political boundaries
Dispersal - indigenous species
Impetus for dispersal:
Response to negative ecological interaction,
normal part of life history
Factors limiting dispersal:
Species mobility, physical barriers, biological barriers, climate (physiology), food (preferred), predators/competitors
Dispersal - nonindigenous species
Impetus for dispersal:
Humans!
Food, sport, biological control, unintentional
Factors limiting dispersal:
biological barriers, climate (physiology), food (preferred), predators/competitors (<)
Policy, education, outreach
What makes a good nonindigenous species (NIS)? **
High reproductive rate, including high fecundity, short interbreeding period
Short generation time with rapid maturation
High dispersal rate
Broad native range, abundant in native range
Tolerant of a wide range of water quality
Ecological generalist with respect to habitat and tropic requirements
High genetic variability and phenotypic plasticity
Mechanisms for successful invasion - replacement
Habitat degradation creates conditions that are no longer favorable for native species, but are acceptable for introduced species
Anthropogenic disturbance (siltation, dredging, climate change)
Natural disturbances (flooding, storms)
Implies that native species are specialists and introduced species are generalists
Does not require interaction between native and introduced species
Replacement related to disturbance
Correlation of native and introduced species with land use intensity in southern Appalachian streams
Mechanisms for successful invasion - displacement
biotic interactions in the form of predation, competition, or introduced parasites and diseases
Introduced species prey on native species
Competitive exclusion principle (both species vie for the same food, space, reproductive habitat)
Novel parasites & diseases found in introduced species infect native species which have not evolved defenses against them
Most successful invasions generally occur as a result of both ____ and _____
replacement and displacement
In some cases, habitat that is successfully invaded typically has been modified by humans leading to decreased habitat diversity and variability
Nonindigenous aquatic plants
Dispersal through seeds (propagules), fragments, whole plants
Aquatic macrophytes, wetland vegetation, algae
Biological impacts - shading, sequestration of nutrients, increased decomposition and oxygen depletion
Human impacts - navigation, aesthetics, loss of sport fish, toxic algal blooms
Nonindigenous aquatic invertebrates - zebra mussel (Dreissena polymorpha)
Native to the Black, Caspian, and Azov Seas
Filter feeder, pelagic (veliger) larvae
Potential for rapid colonization
Release of larval mussels during the ballast exchange of a single commercial cargo ship traveling from the north shore of the Black Sea to the Great Lakes has been deduced as the likely vector of introduction to North America
Rapid dispersal throughout the Great Lakes and major river systems was due to the passive drifting veliger larvae, and its ability to attach to boats navigating these lakes and rivers
Biofouling capabilities by colonizing water supply pipes of hydroelectric and nuclear power plants, public water supply plants, and industrial facilities
Reduced the biomass of phytoplankton significantly following invasion
Nonindigenous fishes - lionfish (Pterois volitans) **
Native to Indo-Pacific
Sit and wait predator, poisonous spines
Popular aquarium species
Lionfish in the Western Atlantic:
Numerous studies now being conducted to determine the impacts of lionfish – the first nonindigenous marine fish to establish the Western North Atlantic and the Caribbean
What are the potential impacts of lion fish on coral reef ecosystems?
Negative net recruitment of important native reef fishes
Also prey on juvenile spiny lobster
Ecological, economic, and human health considerations
Source of climate change
Rapid increase in the emission of greenhouse gases
Increase in slash and burn land clearing (emissions and loss of carbon sink)
Population growth, industrialization, and ignorance
Direct impacts of increasing water temperature on fish (negative) **
Physiological – temperature beyond tolerance limits (critical thermal maximum) can lead to mortality
Increased metabolism and energetic needs
Decrease in growth if prey production is insufficient
Increase in water temperature occurs more rapidly than selective pressures that allow populations to persist
Direct impacts of increasing water temperature on fish (positive) **
In some cases survival may increase, especially in temperate regions since constraints of size-dependent overwinter starvation would be relaxed
Also, greater annual growth could occur for coldwater, cool water, and warm water freshwater fishes because an increase in the length of the growing season and the volume of habitat offering preferred temperatures
Collective impacts could result in modified species ranges, both with latitude and with elevation
What are effects of climate change beyond warming?
Precipitation regimes will also be altered
Climate change will bring more extreme weather patterns, including droughts, wildfires, heavy rainfall, and storms (e.g hurricanes)
Increased desertification in additions to rapid deforestation = reduction in carbon sinks, increased heat absorption of land, reduction in groundwater and surface water flow
Reduction in global cloud cover - feedback mechanism that accelerates warming because of decreased albedo
Impacts of climate change on the water cycle
Non-uniform changes in precipitation, more severe extremes (longer droughts, more intense floods)
Loss of polar ice caps, increase in sea levels, potential reduction in the deep western boundary current in the Atlantic
Cascading impacts of climate change
Changes in carbon input and nutrient loading, influencing primary production
Changes in sediment loads and the mobilization of contaminants
Changes in habitat availability; increase in nonindigenous species; changes in movement patterns
Changes in recruitment dynamics of invertebrate, plant, and fish populations
Change in community composition
How does ocean acidification affect coral? **
Zooxanthellae – symbiotic algae living in the tissue of corals
Provides the color of corals
Excess production of glucose, glycerol, and alanine for host
Provide the energy for coral to create CaCO3
Zooxanthellae are expelled when the coral is stressed (from acidification or heat stress)
Reduced secretion of CaCO3
Decoupling disturbances
decoupling = reducing the amount of resources used to generate economic growth while decreasing environmental deterioration and ecological scarcity
Overharvesting of fish
Coral bleaching related to temperature
Nutrient loading and freshwater input
Loss of herbivores
Increased growth of macroalgae
Baselines
an important reference point for measuring the health of ecosystems; provides information against which to evaluate change; it’s how things used to be
Important to keep track of how things have been because baselines are shifting (ex: people visiting degraded coastal environments and calling them beautiful, unaware of how they used to look)
