Resource Utilization in Heterotrophic Vs Autotrophic Marine Shrimp Production

Abstract

<b><sc>Abstract </sc></b>Limited-discharge bio-floc technology applied to marine shrimp production within recirculating aquaculture systems has gained popularity over the last 20 years. There are two approaches to biofloc shrimp production; 1) Autotrophic water treatment utilizing either, nitrifying bacterial growth or, photosynthetic culture utilizing algal growth or, 2) Heterotrophic water treatment utilizing organically supplemented bacterial growth to maintain control over potentially toxic ammonia and nitrite levels within the culture system. The major operational difference between nitrifying biofloc culture, as opposed to heterotrophic culture, is the C/N ratio of the input feed. Marine shrimp culture fed a 36% protein feed functions at an input C/N ratio of ~ 8.7/1 whereas heterotrophic culture system requires supplemental input of organic carbon in addition to feed to support bacterial growth to remove ammonia nitrogen, typically resulting in an input C/N ratio of 12-15/1. A prototype nitrifying marine shrimp production system is projected to yield 22-23 count shrimp at 45,000 lb/acre every 120 days as compared to a heterotrophic system yielding 45,000 lb/acre every 90 days. The primary advantage of the heterotrophic system is more immediate/rapid control of ammonia and nitrite levels. However, the major disadvantage is substantial carbohydrate requirement (0.86 lb-sugar/lb-feed). In addition, the heterotrophic system would produce in excess of 600,000 gallons of sludge (at 2% solids) that would need handling and disposal, as opposed to 200,000 gallons of sludge produced from an autotrophic system.