Abstract: A system for continuously collecting and preserving fish eggs and larvae by pumping, concentrating, separating, and preserving samples for a specific period of time or volume. Water containing fish eggs and larvae is pumped by a centrifugal pump through smooth-walled plumbing into a headbox. Water flows out of the headbox over a sheet-metal ogee crest down over an inclined panel and then across a wedge-wire screen. Water with retained material drops through smooth-walled plumbing and a swing-joint union into a diverter arm. The swing-joint union is coupled through a chain and sprocket to a stepper motor programmable to position the diverter arm over each of the sample buckets. A peristaltic pump operates on a preset time and delivers a calculated concentration of formalin to a previously filled sample bucket.