Introduction

Photo by Craig Kasper

Fish Eat Many Different Foods! Herbivores

-small stomachs and long intestine tilapia carp

Omnivores -moderate size stomach and intestine

catfish

Carnivores -large stomach and short intestine

trout striped bass

After water qualitynutrition is often the driving force behind most successful fish culture.

Photo by Craig Kasper

What is nutrition?What is nutrition?

A process where an organism takes in food, breaks itA process where an organism takes in food, breaks itdown, absorbs it, and uses the energy and nutrientsdown, absorbs it, and uses the energy and nutrientsit contains to make body tissues, move around orit contains to make body tissues, move around orreproduce.reproduce.

Photo by Craig Kasper

Nutrition for fish means feeding something...

Supplements : fertilizers which stimulate phytoplankton and zooplankton to grow in pond. (Fish then eat these organisms.)

Complete feeds: Provide all nutritional needs of fish: pellets or flakes

Why feed fish?Why feed fish?

Courtesy: Scott Stensland

““You must feed a fish to grow You must feed a fish to grow a fish!”a fish!”

Auburn Fisheries and Allied Aquaculture

Other Reasons to Feed Fish Feeding fish increases production over

not feeding, or fertilizing alone.

ex. 400lbs./acre (fertilizer) vs. >7500 lbs./acre (complete feed)

i.e. more fish can be put into a pond or tank!

More fish means more money (profits)!

Objective 1: Calculation of Feed Conversion Ratios& Economics of Feeding Properly

Auburn Fisheries and Allied Aquaculture

Aquatics vs. Other AnimalsAnimal Feed Conversion RatioTerrestrial lbs. feed/lbs. weight gain

Cow 8:1Pig 3:1Chicken 2:1

AquaticsTilapia 1.5:1Catfish 1.1:1

Why are fish better?

FCR Formula Calculation

FCR = Total pounds of feed fed Total pounds of fish weight

gain

FCR = 10 lbs feed fed8 lbs fish weight gain

FCR = 1.25: 1 (a very good FCR!)

Auburn Fisheries and Allied Aquaculture

Feed Conversion vs. Cost

NOTE: Ensuring good feeding practices helps NOTE: Ensuring good feeding practices helps maintain a good FCR and lower operational costs maintain a good FCR and lower operational costs associated with feeding! (Source: Catfish Farmer’s associated with feeding! (Source: Catfish Farmer’s Handbook, Robinson et al. 2001)Handbook, Robinson et al. 2001)

AQUCULTURE NUTRITIONAQUCULTURE NUTRITIONObjective 2: Larval vs. Adult FoodsObjective 2: Larval vs. Adult Foods

Larval Cobia: VT-VSAREC

Would you feed these fish the same sized food?

Adult Sturgeon (average weight 20 kg).

Juvenile Sturgeon (0.1 kg)

doc K ©2007

doc K ©2007

Diversity of Species

Over 40,000 spp. (marine & freshwater) many have larval stages.

Delicate fish which require special care and special foods.

Small mouths mean small food.

Many eat phytoplankton and/or zooplankton as first food.

Nutritionally good! 60% protein 15% lipid

Phytoplankton Production: Food for Food? Micro-algae can be used to feed fish or other

aquatics

which can’t eat larger food. Cell Size 4-8 microns Species

Isochrysis Nannochloris Chlorella

Costly! Must be sterile! Population crashes possible.

Photo by Craig Kasper

Rotifers: the next step

Highly productive Laboratory

production 100 to 200+ m size 2-3 week life span small size suitable as

first food

Feeding Marine Larval Fish

Rotifers Typical first food in

hatchery Feed algae or yeast Enrichment needed

© Fisheries and Allied Aquacultures Image Gallery

Artemia

Feeding of older larvae Last live item of larval fish before

training to commercial (adult) feed. Can be hatched or purchased frozen.

© Fisheries and Allied Aquacultures © Fisheries and Allied Aquacultures Image Gallery Image Gallery

Isopods, Copepods, Barnacles, Amphipods... all Isopods, Copepods, Barnacles, Amphipods... all potential meals for young fish!potential meals for young fish!

Yet provision of these animals is often difficult Yet provision of these animals is often difficult as they are also fragile.as they are also fragile.

© Fisheries and Allied Aquacultures Image Gallery

Adult Fish Food

Unlike larval fish, adults aren’t usually limited by gape size (small mouth).

The challenge in adult fish is getting them to eat something that is manufactured vs. live!

Fish food comes in all shapes and sizes: flakes, pellets, sticks, meals, gels, micro capsules (think vitamins).

Many fish food varieties!

Flakes

Aquatic animal pellets

Algae Discs ©doc K 2009©doc K 2009

©doc K 2009©doc K 2009©doc K 2009©doc K 2009

Larval vs. Adult Diets

Larval AdultProtein 55% 30%-40%

Fat 15% 4-10%

Size 4-200 µm 1 mm-10 mm

AQUCULTURE NUTRITIONAQUCULTURE NUTRITIONObjective 3: Pros and Cons of Live vs. Commercial FoodsObjective 3: Pros and Cons of Live vs. Commercial Foods

Fish Advantages, or Not?

Aquatics need a lot of dietary protein!

They can’t tolerate much dietary carbohydrate.

Fish require dietary omega-3 fatty acids.

Fish can absorb some minerals from water.

Most fish can’t synthesize Vitamin C.

REM: Larval vs. Adult Diets

Larval AdultProtein 55% 30%-40%

Fat 15% 4-10%

Size 4-200 µm 1 mm-10 mm

Live foods: algae, brine shrimp, daphnia, etc.Pros Protein: >40% Fat: >10% Great for small fish, but impractical for larger

ones (why?)

Cons Cost: $$$$ Feeding: often must be fed by hand Labor/storage: skilled labor needed to raise

animals and maintain culture conditions. Population crashes likely.

Commercial foods:

Pros Protein: 28-50% Fat: 4-16% Any size available Much cheaper than live food Easy to feed Storage easy.Cons Nutrient composition can be inconsistent. May not provide all nutrition to all fish Fish may not eat diet if spoiled Diet may not be nutritionally complete for some

species Diets must be kept dry and cool at all times

AQUCULTURE NUTRITIONAQUCULTURE NUTRITIONObjective 4: Importance of Ingredients in Fish FoodsObjective 4: Importance of Ingredients in Fish Foods

Photo by Craig Kasper

Animal Ingredients Protein sources in aquatic feeds: Fish Shrimp/crab Feathers Soybeans Meat/Bones Eggs

Animal proteins also provide excellent flavor

Protein is the main nutrient in fish feeds 28-55%

Size dependent nutrient needs: Fry > Fingerlings > Stockers > Adults/Brood stock

Fish meal Challenges Reduction of dietary fish meal is a primary challenge

Why?

Competition for usage from other agriculture industries

(swine, poultry, etc.)

Variable nutrient composition (proteins and fats)

Finite resource

Expensive!

Fish Meal Usage

17

55

20

23

48

17

35

24

29

0%10%20%30%40%50%60%70%80%90%100%

1988 1998 2000

OthersSwinePoultryAqua

30 MMT30 MMT

Grains: Carbs!

• Some fish can tolerate high carbohydrate feedsSome fish can tolerate high carbohydrate feeds

tilapia carp catfish pacutilapia carp catfish pacu

• Spares protein for muscle synthesisSpares protein for muscle synthesis

• Cheap dietary energy sourceCheap dietary energy source

• Many sources:Many sources:

wheat corn wheat corn

yucca plantainyucca plantain

Grains:challenges

Plant feedstuffs generally low protein exception: soybean meal (high protein)

Plant feedstuffs contain toxins or “antinutritional” factors

such as phytic acid, trypsin inhibitors, lectins, etc.

-decreases weight gain or prevents fish from eating food.

-could harm the environment.

Fat Sources Fish and animal oils, lard, soybean and corn

oils

Fish require from 4-16% dietary fat.

Energy source of feeds, spares protein for growth

Provides flavor!

Certain fatty acids required: 18:2n-6 (Linoleic), 18:3n-3 (Linolenic) = freshwater fish 20:4n-6 (Arac. acid) = healthy immune response 20:5n-3 (EPA); 22:6n-3 (DHA) = saltwater fish

Fat Challenges

Too much, or wrong ratio, decreases growth, harms liver & decreases cold tolerance

When reducing animal products in feeds, lipid requirement harder to reach (esp. marine fats)

Fish oil remains the best source of EPA and DHA