In ancient Hawaiʻi, fishponds were remarkably successful in ensuring a steady supply of food. In modern times, these seafood “farms” can greatly relieve pressure on wild stocks and supplement market demands – especially local species that are increasingly important economically. 

Yet, efforts to revitalize this traditional aquaculture have encountered challenges. For example, fish introduced into the fishponds to enhance stocks often have low resilience. And for some species of high economic interest, there’s also a lack of reliable reproduction techniques.

But with biennial Sea Grant awards in hand, two new aquaculture track projects led by Andre Seale of the Dept. of Human Nutrition Food and Animal Sciences are addressing these problems. His twin studies employ two local species of interest for sustainable aquaculture development: the sea cucumber (Stichopus horrens) and ʻamaʻama, or striped mullet (Mugil cephalus). 

The grants have also enabled Andre to add graduate assistants Tyler Goodearly and Reilly Merlo, who are enrolled in the Nutritional Sciences PhD program, as co-investigators. 

Sea cucumbers

To improve the productivity of these echinoderms, Andre and Tyler will partner with local producers, fishpond managers, and collaborators to devise a species-specific approach for inducing oocyte maturation and spawning behavior while assessing the viability of larvae. The researchers hope the knowledge gained will provide a framework for overcoming the reproductive dysfunction of Stichopus horrens and reliably producing sea cucumbers in Hawai‘i. Ultimately, it could spearhead national sea cucumber production efforts and lead to practices that will optimize growth in sustainable aquaculture systems, including Hawaiian fishponds.

“This sea cucumber is a good candidate for aquaculture, given its fast reproductive life cycle, ecosystem services rendered as sediment feeders and high value in Asian markets” Andre says. 

Striped mullet

Natural recruitment of the ʻamaʻama, or juvenile striped mullet, to fishponds has become unreliable. What’s more, the introduction of hatchery-raised fry directly into the fishponds has been largely unsuccessful.

In order to better understand how to improve rearing practices and stock enhancement of this species, this project aims to establish strategies to adjust the fingerling hatchery environment in order to precondition the ʻamaʻama, improve their environmental resillience, and optimize their survival and growth once introduced to a Hawaiian fishpond setting.

Andre and Reilly will focus on the effects of variable salinity and temperature regimes on physiological markers of growth, stress, and salt-and-water regulation in the fish. This will help establish which environmental conditions can best prepare the juvenile mullet for survival in the natural fishpond setting.

“In addition to informing management strategies for rearing the ʻamaʻama in fishponds, the results should also provide further insight into how these native fish might adapt to future changes in climatic conditions,” Andre says.

Read: “Development of gonadal maturation and spawning strategies in Hawaiian sea cucumbers.”

Read: “The development of environmental acclimation-based rearing strategies to optimize survival and growth in amaʻama or striped mullet, Mugil cephalus”