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Shellfish Assessment Program - Culturing Research: Past Research

The Effects of Holding Space on Juvenile Red King Crab Growth and Survival

Photo of a juvenile red king crab reared in holding container

Rearing crustaceans communally for aquaculture, stock enhancement or research often results in high rates of cannibalism and low yields. One potential strategy to reduce loss from cannibalism is to rear crustaceans in individual cells.As small holding cell size can result in decreased growth or increased mortality, it is essential to identify the optimal holding cell size, both for mass culturing efforts and for experimental design purposes.

In this study, we reared juvenile red king crab (3.67 to 8.30 mm carapace length) in 20, 40, and 77 mm diameter holding cells and monitored growth and survival over a 274 day experiment. A trend of lower growth per molt in the smallest holding cells resulted in crab 17% smaller than those in the large holding cells at the end of the experiment. Additionally, mortality rates were an order of magnitude higher in the small holding cells compared with the large or medium cells. For individual rearing of this size of juvenile red king crab, the medium-sized cells (40 mm diameter) are the optimal size as there was no increase in mortality and only marginally lower growth rates compared to the large-sized cells.

Photo of many reared juvenile red king crab in separate holding containers

A Quantitative Model Applied to the Development of Crustacean Larvae

Graph of king crab development from first zoeal stage through first crab stage

Scientists like to use mathematical equations to describe things that occur in nature. These equations are useful to describe processes simply and to make predictions. For example, Newton derived a series of equations to describe how objects move. In biology, many processes are described in terms of transitions between stages. For example, crab larvae generally pass through a number of larval stages. The larvae pass from one stage to the other by molting.

Up till now, a mathematical model that describes the transitions between multiple stages has not been developed. To fill this void, Research Ecologist Chris Long, developed a multiple-stage transition model to describe such processes. In a demonstration of the model he fit it to data on larval development of red and blue king crabs (Paralithodes camtschaticus and P. platypus). The model fit the data well and provides useful estimates on how quickly the larvae of these species will develop that could be applied to larger population models.

Larval development of red and blue king crab from the first zoeal stage through the first crab stage. Points represent the mean stage 1 standard error. Lines represent the best fit stage-transition model for each species. The larval stages are the 4 zoeal stages (ZI-ZIV), the glaucothoe stage (G), and the first crab stage (C1).

Blue King Crab, Paralithodes platypus, Development of Larval Cultivation Techniques

Photo of a blue king crab

Blue king crabs have a 2-year reproductive cycle. In January-February of their spawning year, female crabs molt and mate, and extrude about 150,000 eggs that are then fertilized and attached to the female's abdomen. The females carry the developing fertilized embryos for approximately one year. The next year, larvae are released or hatched, but the crabs do not molt or mate again, unlike red king crabs, which hatch, molt, mate, and extrude each year.

Photo of blue king crab embryo at the four cell stage
Click HERE for more embryo images!

In 2003, Shellfish Assessment Program received a grant from the North Pacific Research Board (NPRB) to study the early life history of blue king crab. In July and October 2003, 21 female blue king crabs were captured from the Bering Sea and were maintained at the Kodiak Lab. In January 2004 one of the old-shell females molted, mated, and extruded a new clutch of eggs. Embryos were photographed at daily intervals.

Shellfish Assessment Program - Culturing Research CURRENT RESEARCH

Related Publications

  • LONG, W. C. 2016. A new quantitative model of multiple transitions between discrete stages, applied to the development of crustacean larvae. Fish. Bull., U.S. 114:5866. Online

  • SWINEY, K. M., W. C. LONG, and S. L. PERSSELIN. 2013. The effects of holding space on juvenile red king crab, Paralithodes camtschaticus (Tilesius, 1815), growth and survival. Aquaculture Res. 44:1007-1016.

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