SUSTAINABLE MARINE AQUACULTURE   •   TROPICAL AQUACULTURE
BIVALVE AQUACULTURE   •   FRESHWATER CULTURE OF MARINE SHRIMP
INTENSIVE SEAWEED CULTURE   •   AQUACULTURE OF BIOMEDICAL SPECIES

Sustainable Marine Aquaculture

DEVELOPMENT OF A MODEL FOR LARVAL GROWTH AND FEEDING ABILITY IN SOUTHERN FLOUNDER, PARALICHTHYS LETHOSTIGMA

Research Team:
Marty Riche (USDA) - Principle Investigator
Rikke Bachmann
Ken Riley

One of the most important factors affecting the success of a feeding regime for larval marine finfish is the availability of live prey that are within the size range that the fish larvae are able to eat. If the prey is too large, the fish larvae will not be able to swallow it. If it is too small, the larvae will expend an excessive amount of energy capturing the number of prey items needed to meet there nutritional requirements. This study was undertaken to identify the optimal prey size for larval southern flounder as a function of larval age and body length.

Larval southern flounder (Paralichtys lethostigma) were reared and sampled daily for 50 days post-hatch (N=230). Samples were preserved in 10% buffered formalin, and filmed using a dissecting microscope. Computer image analysis was used to measure larval lengths, upper and lower jaw lengths, and mouthgape. Mouthgape (was calculated from the upper and lower jaw length using the following formula:

c = (a2 + b2) 0.5

where,

c = mouthgape
a = upper jaw length
b = lower jaw length

Research conducted elsewhere has demonstrated that the optimal prey width for other species of flatfish is about 36% of the mouthgape. Table 1 shows the relationship between larval standard length, mouthgape, and optimal prey width.

Table 1: Relationship between larval standard length,
mouthgape, and optimal prey width (36% of mouthgape)


Commonly used live feeds for southern flounder larvae include s-type rotifers (Brachionus rotundiformis), first instar Artemia nauplii, and enriched Artemia metanauplii. The dimensions of these common prey types is presented in Table 2:

Table 2: Size of live feeds


The data on mouthgape, optimal prey width, and the size of the different types of live feeds allows for the development of a feeding regime optimized for prey size.