Christian Lawrence

A Novel Method for Rearing First-Feeding Larval Zebrafish: Polyculture with Type L Saltwater Rotifers (Brachionus plicatilis)

Promoting high rates of growth and survival can be a major challenge in zebrafish culture, especially during the first-feeding stage. Here we describe a new rearing technique in which zebrafish larvae are polycultured in static tanks with Type L saltwater rotifers (Brachionus plicatilis) for the first 5 days of feeding (days 5-9 postfertilization). To demonstrate the effectiveness of this technique, we conducted rearing trials using fish from two different strains: AB and nacre. Growth, survival, water quality, and rotifer density were assayed daily through the polyculture phase (days 5-9), and during the transition to standard rearing conditions (days 10-12). After that point, once the fish were fully integrated onto recirculating systems, parameters were measured once per week out to day 30. In all trials, the fish displayed high rates of growth and survival throughout the three phases (polyculture, transition, and recirculating flow), indicating that this method may be employed during the critical first-feeding stage to help improve rearing performance in zebrafish facilities. Additionally, water quality parameters observed during the polyculture phase of the trials reveal that early zebrafish larvae are much more tolerant of elevated levels of ammonia and salinity than previously believed.

The Effect of Stocking Densities on Reproductive Performance in Laboratory Zebrafish (Danio rerio)

Despite the growing popularity of the zebrafish model system, the optimal husbandry conditions for this animal are not well defined. The aim of this study was to examine the effect of stocking density on reproductive performance in zebrafish. In this study, undertaken by eight different zebrafish facilities, clutches of at least 200 wild-type zebrafish embryos from a single pairwise mating were produced at each participating institution and subsequently reared according to in-house protocols until they were 14 weeks old. Fish were then randomly assigned into treatment groups with balanced sex ratios and densities of 3, 6, or 12 fish/L. After a 1-month acclimation period, fish were spawned in pair crosses every 2 weeks for 3 months, for a total of six spawning dates. The number of viable and nonviable embryos produced in each clutch were counted at 1 day postfertilization. Although there was a great deal of variability in clutch size and percent spawning success among laboratories, there were no significant differences in average clutch size, spawning success, or percent viable among the treatment densities. These data suggest that using stocking densities as high as 12 fish/L does not have a negative impact on performance, when measured by reproductive performance.

Generation time of zebrafish (Danio rerio) and medakas (Oryzias latipes) housed in the same aquaculture facility.

The zebrafish and the medaka are both important model organisms in biomedical research. Both species are frequently characterized as having a generation time of approximately 2–4 months, but the precise onset of sexual maturity and the variability of reproductive success with age have not been previously examined. The authors studied reproduction in replicate groups of wild-type zebrafish (strain AB) and medakas (strain Cab) that were maintained together in the same aquaculture system. Length, weight and survival of the fish were measured and recorded once per week. Reproductive success and viability of offspring were also evaluated. Both zebrafish and medakas began producing viable embryos within 60 d post-fertilization. These findings show that it is possible to successfully maintain populations of both species within the same research infrastructure without compromising reproductive success or embryo viability.

Methods for Culturing Saltwater Rotifers (Brachionus plicatilis) for Rearing Larval Zebrafish

The saltwater rotifer, Brachionus plicatilis, is widely used in the aquaculture industry as a prey item for first-feeding fishes due to its ease of culture, small size, rapid reproductive rate, and amenability to enrichment with nutrients. Despite the distinct advantages of this approach, rotifers have only been sporadically utilized for rearing larval zebrafish, primarily because of the common misconception that maintaining cultures of rotifers is difficult and excessively time-consuming. Here we present simple methods for maintaining continuous cultures of rotifers capable of supporting even the very largest zebrafish aquaculture facility, with minimal investments in materials, time, labor, and space. Examples of the methods application in one large, existing facility is provided, and troubleshooting of common problems is discussed.

Regulatory compliance and the zebrafish.

The growth of the zebrafish as a model organism has so far greatly outpaced regulatory oversight governing its care and use in research. However, the same levels of regulation that characterize the use of traditional mammalian model animals will likely be extended to zebrafish, especially as use of the animal continues to increase. The challenge for both the zebrafish research community and regulatory agents is to ensure that emerging guidelines are sensible and serve to promote quality science and the highest standards of animal care. This brief review summarizes a panel discussion that was convened on this subject at the World Aquaculture Societys Aquaculture America 2009 Conference in Seattle, Washington. The current regulatory environment in the United States is discussed, and a set of generalized recommendations for developing new guidelines is presented.