Restoring and maintaining the few remaining ancient Hawaiian fishponds are important for preserving this nearly 1,000 year old technology. The current problem of low recruitment and production of the keystone species, striped mullet (Mugil cephalus) and milkfish (Chanos chanos), reflects on the deterioration of Hawaii's nearshore fisheries. Hatchery production is possible but regardless of the source of the fry the Hawaiian fishponds must have a balanced ecosystem with phytoplankton and other microorganisms to support the growth of these filter-feeding and grazing herbivores. Microscopic observations of water samples and sediments from Waikalua Loko I'a indicates an extremely low population of desired feed organisms. The standing biomass of fish is estimated to be around 10 grams/square meter. The importance of these factors in the biological restoration of Hawaiian fishponds or loko i'a will be discussed.
Loko i'a that are currently in production have been in continuous production since they were originally built. Even when left unmanaged they are subject to the inflows and outflows of tides and currents. Pua or fish fry are attracted to the estuarine environment within the pond walls or kuapa. After reaching a certain size they may not be able to swim out of the pond due to the 1/2" grate (makaha) that blocks the entrance of the channel (auwai). The striped mullet ('ama'ama) and milkfish (awa) are two species that traditionally represented the health of a loko i'a. They enter the pond as fry during different seasons. Mullet fry (pua 'ama) enter ponds during the winter months. Milkfish fry (pua awa) enter during summer months. Other species enter during their own seasons.
Nursery systems are important in modern mullet and milkfish production. Post-larval fry are grown to fingerlings or larger sizes before being placed in growout ponds. Nursery tanks or ponds are prepared to receive fry. Wherever possible an effort is made to slowly acclimate the fish to their new home environment. The appropriate live feeds and commercial feed are fed until the fry have fully transitioned to the formulated diet. What is often overlooked is the microbial biofilm that develops on tank walls and along the bottom of ponds. As in aquaponics systems waste products from feed digestion are taken up by algae and other microorganisms resulting in a microbial community that often serves as supplemental food for the fry. The nutritional value of this microbial ecosystem, when properly managed, can be important for its contribution to fish growth and health. Such studies have been done in shrimp production systems. It is reasonable to relate a similar importance of microbial communities and biofilm to herbivores and omnivores in loko i'a.