biology of asian carps - fisheries conservation...
TRANSCRIPT
Biology of Asian carpsLife history of bighead, silver, black and grass carps
What we know, and what we’d like to know
Duane C. Chapman USGS Columbia Environmental Research Center
ID - Bighead vs Silver carp
Keel
Keel
ID - bighead vs silver carp
Silver carp
Bighead carp
Reproduction and Recruitment in
Asian Carps
Asian Carp Life Cycle
From Nico et al. 2005
Upstream spawning movement
• Don’t really know how far – Difficult to separate from “wanderings”– Telemetered fish travel “off-screen”– Management need
• Usually associated with rapidly increasing flows
• DeGrandchamp will speak on movement rate
Spawning locations• Based on visual observation, egg collections • Exact requirements unknown
– Thought to be in turbulent areas of rivers– Mouths of tributaries– Probably NOT in small tributaries
• 400 m3/second possible minimum?
• May occasionally spawn in lakes, but eggs not thought to survive
Spawning behavior• Unknown if species migrate/spawn together
– Bighead – silver hybrids– Black carp spawn deeper?
• Literature: Grass, silver and bighead carp active spawners in open water– Jumping from the water– Swimming upside down at surface
• Bouyant flower
– Never observed in the Missouri River
Spawning periods
• Literature: late spring, early summer for all four species– Black carp a bit later and more protracted?– Papoulias – bighead and silver carp have a
protracted spawning season, Individuals with multiple partial spawns per season
Early Life History
• Requirements for eggs and larvae probably often limiting– “Achilles heel” ?
• Literature: Temperature, current, water hardness, turbidity, river length, even vegetation
Egg Requirements• Eggs are heavier than water
– Without sufficient current will sink to bottom• This is thought to be lethal
• Temperature controls development rate– Temperature window ~ 18 – 30 C (64 – 86 F)
• In theory – can calculate minimum length of river from minimum velocity and temperature
River Length Requirements
From Nico et al. 2005
Further Uncertainty?
• Tang, 1960 – bighead, silver and grass carp reproduced in a reservoir with a small watershed
• Other Asian carps (ex. Elopichthys) may have recruited in reservoirs
• Survival of bighead carp eggs in unaerated bags of water and sediment
Nevertheless…..
• All places currently with confirmed self-sustaining populations of bighead, silver, black, or grass carp have access to a large river, with at least 80 km free-flowing.
What does this mean to a manager?
• Reservoirs with substantial river tributaries are at risk for establishment of Asian carps.
• Some uncertainty exists about other yet-to-be-invaded environments
Fecundity and Reproductive Strategy
Fecundity
• Large Asian carps of all species are capable of producing hundreds of thousands, sometimes millions, of eggs each year
• Examples:– Silver carp: 4.2 million : 12 kg fish– Bighead carp: 1.1 million : 18 kg fish– Black carp: 1 million : 4.5 kg fish
Survival
• No parental care and generally extremely low survival
• Thought to be poor at avoiding predators• Strategy:
– Overwhelm high mortality with many eggs– Grow fast and become:
• Too large to eat• Capable of producing many eggs
Implications
• Adult mortality low• Juvenile mortality varies highly between
years– Controlled by environmental conditions
• Population characterized by strong year-classes
• Removal of adult fish (harvest) works against carp reproductive strategy – as shown by Chinese experience and Mike Hoff’s models.
• Variable year-class strength may affect fishing industry
• Unknown what variables will control strong year classes– High water, access to nursery habitat?– Some of these variables might be controllable
What does this mean to a manager?
Asian Carp Feeding
Strategies
Pharyngeal gill teeth
Silver
Bighead
Grass
Black
Highly specialized;
“Novel weapon” theory
Black Carp
Black Carp• Primarily feeds on mollusks – snails,
mussels, clams • Also feeds on insects and sometimes
vegetation • Gape (mouth size) limited (probably not by
shell thickness)– Relatively small mouth:size, but grows to large
size
Corbicula, invasive Asian clam
Native Molluscivores
• Most concern about potential destruction of mollusks, rather than competition with natives
• Native molluscivores include freshwater drum, redear sunfish, and some redhorse suckers, blue catfish (also non-native common carp), none obligatory molluscivores
• See Anita Kelly’s talk
Common carp pharyngeal teeth
Grass Carp
Grass Carp• As adult, almost exclusively vegetarian
– Will take invertebrates and other high protein/calorie foods but insubstantial part of diet.
• Selectivity – Preference for long, thin vegetation– Do not prefer filamentous algae, hard or tough
vegetation, or duckweed– In a pinch can feed on wide variety of vegetation
Grass Carp• Have the capacity to feed little or not at all
for long periods.– Gorge when opportunity presents
• Terrestrial vegetation important, during water rises
– Do not feed in winter Courtesy Josh Dunkle
Feeding behavior(personal observations)
• For items that will not reach teeth (too wide to enter throat) will pull and tear with lips
• Sometimes partially exits water to access terrestrial vegetation
• Uproots littoral grasses by digging into banks, then eats them roots-first– Effect on bank stability/erosion?
Comparison to Native Fish
• No native fish can compare to Grass Carp in vegetation consumption– Herbivory unusual in fishes
• Most concern related to habitat modification rather than competition with native fish
Bighead Carp
Pharyngeal gill teeth
Gill rakers
Bighead CarpGill rakers
Epibranchial organTaste buds, mucous
Mechanical use?
Diet of Bighead Carp• Mostly considered to be a zooplankton predator
– Consumes larger and colonial phytoplankton• Sometimes including noxious bluegreen algae• Has defenses against toxic algae
– “Detritus” (source unclear or varied)• Size of smallest filtered particles ~1/4 width of
gill raker gap (probably due to trapping on mucous)
Diet of Bighead Carp• Gape large, but food items small
– Probably limited by gap between teeth and crushing plate
– Some food items up to 3 mm• Gut long and thin (3.5 – 5.5 X Total Length)
– No stomach– Not robust – no large, sharp food items!
Feeding Behavior of Bighead Carp• Usually considered pump filterer
From Kolar et al, in press
Feeding Behavior of Bighead Carp
• Often, but not always, feed at surface of water, sometimes almost vertically
Feeding Behavior of Bighead Carp• Sometimes also ram-feed (often observed
below Bagnell Dam, Missouri at dusk)
From Kolar et al, in press
Feeding Behavior of Bighead Carp
Bighead carp ram-feeding in Iowa
Feeding Behavior of Bighead Carp• May attempt to break up large items to
manageable particles• Relative importance of different behaviors
unknown• Other behaviors possible
– Sand particles in some diet studies indicate possible bottom feeding
• Adaptable, but require small particles
Feeding Behavior of Bighead Carp• Feeding thought to be relatively continuous
– Stomachless strategy• Usually have full guts in winter
– Gut evacuation rate (and thus, feeding rate) probably low in winter
Winter Surface Feeding
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Comparison to Native Fish• Native filter feeders of basin
– Paddlefish, gizzard shad, bigmouth buffalo– See Ben Gu’s and Schuyler Sampson’s presentations today
• Can consume particles much smaller than paddlefish (an obligatory ram feeder)
Comparison to Native Fish• Capabilities of bigmouth buffalo less well
understood
Comparison to Native Fish• Bigmouth buffalo gill rakers, excised, and
epibranchial organ
Silver Carp
Pharyngeal gill teeth
Gill rakers
Silver Carp
Diet of Silver Carp• Mostly considered to be a phytoplankton feeder
– Sometimes including noxious blue-green algae– Has defenses against toxic algae– Some blue-greens benefit from being eaten
• “Detritus” (source unclear or varied)– Can silver carp effectively feed on bottom?– What else eats this “detritus”?
• Zooplankton, but ineffective on evasive ones
Diet of Silver Carp
• Size of smallest filtered particles much smaller than bighead carp (sometimes less than 4μm[0.00016 inch])
• Size of items probably limited by gap between teeth and crushing plate
Diet of Silver Carp
• Gut extremely long and thin (7.5- >10 X Total Length)– No stomach, continuous feeding– Not robust – no large, sharp food items!
• Bacterial growth in gut may be important part of diet
Feeding Behavior of Silver Carp• Pump Filter feeder• Normally do not pick out individual items of
prey• In Missouri River study, often located in areas
of higher chlorophyll concentration• Feed in schools, like bighead carp• Apparently do not feed on surface like bighead
carp
Comparison to Native Fish
• Silver carp are extremely specialized filter feeders – Feed on extremely small particles– Native fishes normally not consumers of
phytoplankton
Questions• Vast majority of information on diets and
environmental effects of Asian carp feeding strategies is on LAKES and RESERVOIRS
• USA problems are mostly in RIVERS• Rivers are more difficult to study • What are the effects on native species and
riverine environments?
What does this mean to a manager?
• Asian carp feeding strategies are effective and native fishes sometimes may be out-competed, if food resources are limiting. (see Kevin Irons’ talk)
• Asian carps have highly specialized anatomy for feeding, but often show unexpected opportunistic behavior
Finally
• There is still much to understand about biology of Asian carps
• Experiences in other countries useful, but don’t always apply
• Expect the unexpected – Asian carps continually find new ways to break the mold