In recent years, Hazard Analysis Critical Control Point
(HACCP) systems have been actively adopted by the aquatic
food industry. In the field of aquaculture involved in supplying
fish, use of HACCP is under close examination for producing
healthy fish. Mass outbreaks of pathogenic bacterial infections
have killed large quantities of fish in recent years, causing great
financial damage to fish farms. In addition, from the perspective
of food hygiene for delivering safe fish to markets, farming fish
with minimal dependence on antibiotics is important. Periodic
checks of fish health and detection of abnormalities as quickly
as possible are thus necessary at fish farms. Several studies
have shown blood glucose levels closely correlate to the level
of stress in fish and represent the state of respiratory or nutritional disturbance [1–6]. Recent studies have also clarified that
decreased levels of blood cholesterol represent a useful indicator
of reduced resistance to bacterial infection [7,8]. In this manner,
determination of blood glucose and cholesterol is important for
ascertaining the health of fish. At present, these tests are conduced
using clinical laboratory test kits that have been designed
for humans. Furthermore, as each sample needs to be analyzed
separately, testing is time- and labor-intensive. When ascertaining
the health of fish at fish farms, testing as many fish as possible
in a fast and convenient manner is crucial.
Recent research has been actively investigating the development
of biosensors consisting of an immobilized enzyme membrane
and an electrochemical device. We have already developed
a biosensor to measure cholesterol levels in fish plasma, in an
attempt to establish rapid and convenient methods to ascertain
fish health [9]. Since this method is based on flow injection analysis
(FIA), continuous measurement is possible and only 5 min is
needed to analyze each sample, markedly reducing testing time.
However, even this method requires a certain amount of skill