Continuous Underway Fish Egg Sampler

CUFES Concentrator and Sample Collector

The Continuous Underway Fish Egg Sampler (CUFES) is an instrument used to collect pelagic eggs of fish, and the corresponding hydrographic data, from ~3m depth on moving ships.

The CUFES system consists of an inboard or outboard submersible pump, concentrator and sample collector. Water is pumped continuously from a fixed depth (surface to 3 m) to the concentrator onboard the ship. Eggs and similarly-sized particles are retained in the sample collector. CUFES operates continuously under most sea conditions.

On Winter, Spring, and Summer CalCOFI cruises, samples are examined, preliminary egg counts performed, and the samples are preserved for further analysis on-shore. These samples and data are used to investigate spawning habitats and estimate spawning biomass.

CUFES has been used to sample the eggs of sardine, anchovy, mackerels, menhaden, pinfish, and round herring off the United States, Mexico, Peru, Chile, France, Spain, Portugal, and South Africa.


Water is continuously pumped at approximately 600-700 liters per minute from 3-m depth to the concentrator. Particles are concentrated by an oscillating net (e.g. 500 micron Nitex mesh) and the filtrate is discharged overboard.

The concentrate passes to the sample collector, where particles are retained over sequential sampling intervals (5-30 min) on a codend of the same size mesh as used in the concentrator. Fish eggs are usually counted at sea prior to preserving the sample.

Simultaneously, ancillary data are continuously collected (date, time, position, temperature, salinity, and chlorophyll-a fluorescence). The system operates continuously and under nearly all sea conditions, providing a real-time estimate of the volumetric abundance of pelagic fish eggs at the pump depth.

CUFES-derived egg density estimates are regularly calibrated with estimates of abundance made using vertically-towed nets such as the Pairovet or the obliquely-towed Bongo net.

Example Egg Distribution Map