For the past five years, our team has conducted RAS based larviculture research with Domesticated Striped Bass, Morone saxatilis, (distinct from both wild striped bass or hybrid striped bass). The principal foci include system optimization, inert feeds, nutrition, and digestive physiology to improve production during this early life stage. We encountered numerous surprising and unexpected challenges to our basic larviculture protocols. This resulted in additional studies to improve these methodologies and technologies. This presentation will highlight these efforts from a systems approach as outlined below.
Feeding larvae usually begins 4 dph-8dph after mouthparts form. Feeding this early produces excess surface oil, impeding critical swim bladder inflation. We have enhanced the efficiency of our surface oil skimmer, examining airstone placement, lipophilic pads, and surface retainers.
In addition, water depth and water flow rate affect the ability of larvae and fry to eat and impact energy expenditure. We will discuss initial efforts to understand these variables as related to post larval and fry production. Control of these factors is enhanced in recirculating systems.
Artemia nauplii are the most common first feed for carnivorous marine species like domestic striped bass. The process to hatch and deliver healthy nauplii is expensive and time consuming. Our lab has shifted from using a common decapsulation protocol to one using a magnetic cyst shell removal process. This change has reduced labor, while also providing a superior product clean of hatching debris. In parallel, biofiltration performance has been improved.
Larvae require feeding around the clock. Examination of gut contents showed food retention time of about 3 hours, throughout most of the larviculture period. Wi-fi controlled peristaltic pumps were used to maintain uniform provision of Artemia 24/7. Some challenges remain with these units. Systems produced successfully and improvements are underway for season two.