Sea grant researchers developing new stress tes...( RALEIGH NC. North Carol...)

RALEIGH, NC. North Carolina Sea Grant researchers have identified naturally occurring antibiotics in channel catfish that may be a promising indicator for monitoring fish health in the expanding aquaculture industry nationwide. Scientists discovered that fish, under stress, suffer from a decline in polypeptides called histone-like proteins (HLPs). From this scientists hope to develop a commercial stress test instrument.

The scientists found that polypeptides called histone-like proteins (HLPs) are likely an important component of nonspecific immunity in channel catfish. Nonspecific immunity protects against many different diseases at once. Specific immunity protects against only a single pathogen. Thus, in some ways, nonspecific immunity can be considered a "natural broad-spectrum protectant."

In the study, catfish were exposed to chronic stress - from overcrowding and elevated ammonia - for several weeks. This stress caused a significant decline in HLP levels in the skin without any visibly apparent change in the health of the fish. This suggests that HLPs could alert farmers when their fish are at risk for becoming sick, but before any visible clues are present.

"These HLPs were found in the spleen, skin, and gills and are probably in other tissues of catfish," said Ed Noga, professor at North Carolina State University College of Veterinary Medicine. "So these HLPs appear to be everywhere. This is significant because it suggests that HLPs may be important in protecting against many diseases. We also have found these types of antibiotics in rainbow trout and hybrid striped bass."

"This suggests that monitoring HLP levels in the skin - especially during early stages of stress - can help farmers to detect problems before they become catastrophic," said Noga.

The identification of a stress test usable in the field would be important for the aquaculture industry where fish are reared under very high stocking densities, o
'"/>

Contact: Ben Sherman
sherman@nasw.org
202-662-7095
National Sea Grant College Program
26-Apr-2001