Breeding Caridina multidentata in captivity: Opportunities and challenges 

Breeding Amano shrimp, or Caridina multidentata, in captivity combines challenges with unique opportunities. These shrimp, not widely considered economical in the ornamental fish industry due to their complex lifecycle, require a specific breeding process. Amano shrimp produce nymphs that undergo a distinct cycle, starting in freshwater, transitioning to marine water, and then returning to freshwater. This process, different from many other species, often deters hobbyists from captive breeding.

Found naturally in Japan and Taiwan, Amano shrimp are primarily wild-caught, leading to seasonal availability and market shortages. This irregular supply presents an economic opportunity for commercial breeding. Breeding techniques in captivity draw from commercial shrimp aquaculture practices, offering insights for large-scale breeding. Mimicking their natural lifecycle, the breeding process begins with eggs hatching into larvae in freshwater. These larvae are then moved to a marine environment for several developmental stages, before transitioning back to freshwater as juveniles and eventually maturing into adults.

The Amano shrimp's amphidromous life history means adults reproduce in freshwater, while larvae develop in seawater. Mating occurs when the female, after molting, releases pheromones to attract males for external insemination. Fertilized eggs, attached to the female’s pleopods, correlate in number to her size, generally resulting in smaller broods of 200 to 400 eggs due to space constraints.

After hatching, larvae enter nine free-swimming zoea stages before reaching juvenile form. Each stage varies in duration, cumulatively taking up to forty days, and the shrimp bypass a megalopa stage typical in other decapods. As juveniles, Amano shrimp require ample nutrition for growth and frequent molting to accommodate their expanding bodies. This makes them vulnerable to predators.

Maturation takes about 3-4 months, after which the shrimp reach reproductive maturity and can be distinguished by sex. Understanding each stage of their life cycle is crucial for effective breeding and care in an aquarium. To successfully breed Amano shrimp, one must prepare a conducive environment with a sexed pair, stable water conditions, and food. Breeding typically follows the female’s molt, with the female carrying eggs for 3-5 weeks. Larvae, separated using light attraction, are transferred to marine conditions for development. They then require gradual acclimation back to freshwater, simulating their natural transition from rivers through brackish environments.

Post-breeding care in freshwater tanks involves feeding the shrimp a varied diet and maintaining a well-planted, cycled tank. While breeding Amano shrimp in captivity is intricate, it presents an opportunity for economic growth in the ornamental fish industry. By replicating the shrimp's natural lifecycle and leveraging aquaculture knowledge, breeders can tap into this market, ensuring a consistent year-round supply of Amano shrimp.

•    Create a suitable breeding environment with a pair of sexually mature shrimp.
•    Ensure stable water parameters and an adequate supply of food.
•    Sex identification: Females are larger (35-50mm) with brown dashed lines on their bodies and a possible green 'saddle' on the back, indicating ovarian egg development. Males are smaller (25-35mm), identifiable by dots rather than dashes. Sexual maturity is reached at 3-4 months.

•    Breeding occurs naturally in the right conditions, usually after the female molts.
•    Post-mating, the female carries the fertilized eggs for a duration of 3-5 weeks.

•    Transfer the gravid (egg-carrying) female to a separate tank.
•    Use a flashlight to attract and separate larvae, as they are drawn to light.
•    Utilize a pipette to transfer larvae to a marine environment for further development.

•    As the larvae transform into shrimp, they need to be gradually acclimated back to freshwater.
•    This process involves capturing the juvenile shrimp from the marine setting and adjusting them to freshwater over 2-3 days, simulating their natural transition from brackish environments to rivers.

•   Caring for juvenile shrimp in a freshwater tank post-breeding is relatively straightforward.  These shrimp feed on a varied diet, ranging from algae to dead fish. They flourish in well-planted, fully cycled tanks of at least 5-10 gallons, ideally with peaceful fish species as companions.