Fish health 1 Flashcards
what are the infectious agents?
parasites and pathogens
how do parasites and pathogens differ in trophic level strategy than other members of the marine community?
- predators: affect all life stages
- decomposers: affect non-living organisms
Pathogens- what are they?
microparasites, build up in numbers (asexually) from a single infection events
(ie: virus, bacteria)
Parasites- what are they?
macroparasites, recruit to a host and grow (sexually) (ie: sea lice)
Parasitoids-
kill host as part of their development (ie: bacteriophage)
what do parasites/pathogens require to complete their life cycle?
- must recruit a new host
- macroparasites may need several new hosts
what are the three main routes of transmission?
1- free living stage
2-vectors
describe free living stage
- usually an infective stage that exits host through wound or orifice
- usually non-feeding
- short-lived (virus)
- persistent-dormant-nematode egg
- passive(egg) and actively mobile stages to transmit between hosts
describe vectors
- some parasites require a vector to move the infective stage from host to host.
- ie: infective stage circulates in vector blood system (leeches, sea lice)
- parasite might further develop in vector host
- ie: some viruses, worms, trypanosomes.
what percent of known metazoan spp are parasitic?
40% (prob underestimate)
what is the rough proportion of parasitic spp to free-living spp?
at least as many
how is knowing the diversity of parasites and pathogens important?
- diversity of parasites represent a variety of differerent trophic level strategies and life cycles
- helpful in making predictions about potential effects of parasites on marine ecosystems
name some factors which can effect infectious disease dynamics
- warming water temperatures
- acidification
- eutrophication
what are some factors to consider when making predictions about the effects of environmental variables on infectious diseases?
- environmental effect on an individual host and its population density
- environmental factors have non-linear effects on phisiological processes of both hosts and parasites
flashcard notes ended
on slide 10/41
how can stress caused by environmental conditions be a good and bad thing?
- decreasing env. conditions can/will cause stress to hosts
- increased stress: increased susceptibility to infection and parasite numbers increase
- increased stress: cause premature host mortality, reduces disease transmission, decrease incidence of disease
How do environmental factors have nonlinear effects on physiological process of hosts and parasites?
- each spp. has OPTIMAL range of light, oxygen, pH, etc
- shifts in particular environmental variables can disrupt the ability of a well adapted parasites to infect hosts.
- some parasites can adapt to changing conditions or some are extirpated from the ecosystem
- other infectious agents are better suited to the changing conditions and be favored resulting in novel host-parasite interactions and combinations.
what direction of shifts in distribution of infectious diseases will warming likely lead?
latitudinally
Perkinsus marinus (what is it)
protozoan parasite of several marine organisms, severely affects oysters.
how is perkinsus marinus affected by increased weather?
- proliferates at high water temperatures and high salinities as usually seen in river estuaries during drought conditions
- increased water temp along eastern sea board they are spreading rapidly
- now found up to NS
regional warm temperature anomaies have now been correlated with what in the caribbean and pacific?
high coral disease prevalence
what disease is the black abalone along the cali coast to mexico affected by?
what does it cause?
what causes it?
withering syndrome/abalone wasting disease.
- caused by a rickettsia like organism (RLO)
- lethargy, retracted visceral tissue, atrophy of the foot muscle
- although abalone can survive it at low densities and normal conditions, increased VARIABILITY of water temps in intertidal zones increase suceptibility.
- mass mortalities as mean water temperatures increase.
how does increased OA affect pathogens?
growth of Vibrio increased by 13% in lower pH water
how can nutrients promote infectious diseases?
give an example
- increased nutrients increase productivity and host densities, increase parasite/pathogen transmission efficiency
- black band disease on corals
how does variable environmental factors affect parasites/pathogens similarly/differently from their hosts?
similar: variable factors affect them too.
different: their RESPONSES are different
- parasite success are constrained by the environment because their hosts are constrained by the environment
how are parasite/pathogen niches affected by variable environmental factors?
P/P have niches as do free living spp, but changing conditions can push them outside their niche space
-this creates opportunities for other pathogens/parasites to exploit the available resources and hosts.
what are key advantages to studying parasite communities?
- host habitat: parasite community boundary is well defined
- easy to obtain large #s of hosts: replicates easy to obtain
what are some distinctive parasite fauna
- generalist and specialist parasites
- higher proportion of trematodes and acanthocephalan parasites than other vertebrates
same some ecological traits of hosts which have been linked to parasite communities in fish
- size and age
- habitat
- trophic level
- schooling behaviour
- pop’n size and density
- geographic range
- latitude
- depth
how does size/age of host affect ParaComm?
affects the amount of time that a host has been able to accumulate parasites (large fish have more abundant and diverse parasites)
how does habitat of host affect ParaComm?
pelagic fish have fewer parasites than benthic fish (2D/3D)
how does geographic range of host affect ParaComm?
- latitudinal gradient that leads to high diversity near the equator
- this pattern hold true for ectoparasites of fish but not for helminth communities which require life stages within the host
how does depth of host affect ParaComm?
deep sea fishes tend to have fewer parasites than other fish, perhaps due to lower fish DENSITIES
how is the bacteriophage and bacteria relationship similar to the host-predator prey cycle in mammals?
-increased ocean upwelling/increased bacterioplankton/increased phage production/bacterial ppl decrease.
same concept with mammals.
name some conditions where parasites reduce or regulate host ppl or density
- bacteriophages/bacteria: phages most abundant where hosts are abundant
- increased disease prevalence to decrease surging host ppls.
how are increased disease prevalence decreasing surging host ppls?
- ie:
- increase in sea urchin ppl due to reduction in urchin predators
- urchin epizootics cause massive ppl declines and suggest the diseases actually regulate ppl size where natural predators are rare or overfished
read slide 28-31 about otters
might be a question on it
name some mass mortalites caused by infectious diseases
1930s: 90% of eel grass on both coasts affected by slime mold-like
protist
-mass urchin (diadema antillirum) die-off in the 80s, suspected fungus, 95% ppl.
-1995: fungus attacked sea fans, 20-90% of fans died, 50% of caribbean fans lost.
Caribbean Elkhorn and Staghorn coral have been in wide decline due to what?
- white band disease (Vibrio)
- white pox disease
how can para/paths alter entire communities?
- increase/decrease coexistance among competitors
- drive host densities to lower levels
- change behavior of dist’n of host dynamics within the community, especially w/ keystone spp.
slide 35/41. density dependent transmission.
talk it over, ask questions. can’t figure it out!
how can infectious diseases have indirect effects on coexistance and competitions withing a community?
- INTERACTIONS among COMPETING SPP can be effected by infectious disease.
- infectious diseases can DECREASE COEXISTANCE when there is variation in tolerance of infection among competing host spp.
- less tolerant spp become at a DISADVANTAGE: more tolerant spp will outcompete for resources.
give an example on indirect effects of infectious disease to ppl diversity
eelgrass beds were infected by wasting disease
- loss of nursery habitat for fish and waterfowl
- extinction of eelgrass limpet
break down the percentages of infectious diseases which affect fish
25% viruses
34% bacteria
19% protists
18% metazoans
how does trophic level affect ParaComm?
some parasite spp are only foundin one host of a specific trophic level. when these parasites are found in other non-host spp there may have been a change in the environment or host
how does schooling behavior affect ParaComm?
parasites with little need to use vectors, free swimming stages as new hosts in very close proximity at all times.
whats the relationship between oystercatcher and littleneck clams?
- oystercatchers eat clams
- oyster catchers are host to adult trematodes
- poop eggs
- trematodes attack clam foot, prevent them from burrowing away from the birds
- prevent the clam populations from exploding
what are some essential information to consider when managing a fishery
- biology of the fish being harvested/exploited
- understand how the fishery interact with the fish spp being exploited (capture techniques)
- how the fish respond to exploitation
- how other spp share their habitat and how the local ecology will respond with exploitation of one spp
different management approaches must be taken depending on whether the fish are:
- territorial
- only exist in discrete patches with little exchange between similar patches found regionally
- exist in patches but DO have exchange with similar patches through mechanisms such as larval dispersion
- are the fish PELAGIC and have a uniform distribution which may or may not change with season?
- –> all affects both the SAMPLING and MANAGEMENT decisions for a fishery
how are fish generally managed? (large scale)
as a stock or population, not as a species
Depending on habitat-type, different stocks may respond differently to exploitation due to differences in
- food availability
- predators present in the area
- primary productivity
who is the current minister of fisheries and oceans?
Hunter Tootoo
TAC
total allowable catch
- management approach
- fish scientist assess the fish stocks and suggest a MAX amount of fish that should be caught to keep the stock stable or in equilibrium
- then FISH MANAGERS decide if the suggested TAC is politically acceptable and assign the fishery TAC
EEZ: what is it and what is the objective of it
economic exclusive zone
-enhance the conservation and economic management of world marine fishery resources
what is one of the most dramatic and depressing examples of fishery management failure under the EEZ regime
Grand Banks of Newfoundland groundfish.
what are the causes of the cod fisheries crash?
- before the EEZ was in place the grand banks were being harvested by global fishery efforts, already depleting stocks
- equipment and technology increased, increased volume landed
- this increased from small limiting vessels to supertrawlers with high tech fish finding equipment
what did the east coast fishermen replace the cod with as their targeted spp?
queen crab = snow crab, northern shrimp, other invertebrates
in 2010, how much of the original stock of cod had recovered?
10%
what is the largest certified sustainable fishery in the world?
alaskan pollock
what amount of the world’s fisheries has been underestimated over the last 60 years?
more than 50%
what is the hydra effect?
- where a higher death rate in a particular species ultimately increases the size of its population
- adverse changes in the environment that reduces the growth rate of a population may ultimately lead to greater numbers.
how can some fishing activities increase infectious diseases?
- bitter crab disease
- small amount of crab meat infected will contaminate the entire lot.
- when crabbers notice an infected one they huck it overboard, essentially spreading the disease to new areas
