Seed production of red abalone (Haliotis rufescens) in Monterey region – California (USA) – Video

Video description: Peter Hain (USA) and Abdel Rahman El Gamal (Founder of the video channel)

I filmed this video during my visit to this facility on 22 January 2015 where I received a warm welcome from Mr. Peter Hain, the manager of the facility who toured me around the facility. This facility is located in “Moss Landing” in the Monterey region, California.

This facility could be classified as possibly the smallest commercial hatchery/nursery in the state. The collaborators are Monterey Abalone Company collaborates with the Moss Landing Marine Laboratories.

During the visit and as seen in the video, the hatchery component was described verbally as we were out of the spawning season for the abalone, while the spat nursing was adequately covered. The hatchery and nursing facilities and operations are described in the following components:

Source of hatchery broodstock: There are two sources of the red abalone broodstock:

From the wild:  Gravid abalone females and males are collected in season at a site north of Fort Ross, California, under permit from the California Department of Fish and Wildlife.

From other farms/hatcheries:  Gravid females and males are also purchased as needed from two commercial abalone farms and are spawned together with Monterey Abalone Company broodstock and the wild broodstock to increase and maintain genetic diversity.

Sex ratio of broodstock:  In general a ratio of three females to every male is used when spawning commercial farm broodstock.  The ratio can be reversed if crossing large wild females with smaller farmed males.

Spawning season: Wild abalone broodstock from the Northern California coast are generally gravid during the months of March and April, sometimes into early May.  Collection trips are planned to take advantage of favorable weather.  The hatchery phase generally begins in May and extends into June and July.  If any of the initial settlements are poor then additional spawns can occur in August to early September.

Water source and quality during the hatchery operations:

Filtration: Filtration through sand filters (20 microns).   Sand filtered seawater is delivered to the hatchery from the pumping station.  The seawater intake is located approximately 300 meters offshore at 16.6 meters depth.  Hatchery water is further filtered through 20 microns, 10 microns, and 5-micron cartridge filters.

Sterilization: A UV sterilizer is used during the spawning of the adults and hatch-out of the larvae.  The UV sterilizer is generally turned off on Day 3 of the eight to nine-day larval cycle to introduce the larvae to the natural mix of bacteria present in the seawater.

Fecundity:  Large wild females can spawn upwards of eight million eggs with smaller, 4-5 inch, farm animals producing up to one million each.

Incubation: Fertilized eggs will generally hatch in eighteen to twenty hours, dependent on temperature, as trochophore larvae at which point they are transferred to a conical bottom tank with flow-through water and retained with 70-micron banjo screens.  Water flow is maintained at six exchanges per day as the larvae, now veligers, develop.  Generally by Day 8, once again dependent on temperature, the larvae are beginning to show settling behavior.  The larval foot has developed and once this final development stage is reached the larvae are settled the next day into the nursery tanks. 

Larvae develop in the incubator but should be moved to the nursery before the settlement (Should not allow settling in the incubator).   Red abalone larvae in particular are capable of adhering strongly to surfaces and should not be kept in the Larval Rearing Tank any longer than necessary.  

Larval rearing tanks: The conical bottom larval rearing tank holds 454 liters and the ideal density is around five larvae per milliliter.

Production cycle: The hatchery production cycle lasts 8-9 days, depending on temperature, generally 13-15 C.

Abalone Nursing

Nursing capacity: Based on the current volume of nursery tanks, the capacity of the nursery facility is 120,000 – 130,000 abalone spat (seed).

Water source and management: Monterey Bay is the source of water whereas water is pumped from 300 meters offshore and from 16.6 meters under the surface. Water passes through sand filters which filter down to around 20 microns. The filters are backwashed as required by a PLC monitoring system. Filtered water is directed to nursery tanks as required.

Water temperature: 15C is considered ideal but the range is generally 12 to 16C.

Water salinity: Abalone prefers oceanic salinity of 32-36 g/L and will suffer mortality if salinity drops below 25 g/L for an extended time.

Water renewal throughout the nursing:  During the majority of the nursery phase a renewal rate of every two hours is sufficient to maintain water quality although that rate would be increased if, for instance, heavy rain were forecast.  Once the juvenile abalones are beginning their transition to macro seaweed the renewal rate is increased to once per hour.

Nursing tanks: There are four nursery tanks of 5×10 feet with a depth of 50 cm and four tanks 2×8 feet.

Nursing tanks are equipped with settling racks, holding corrugated fiberglass sheets, are locally made of PVC to provide a large surface area.  The surface area available for settlement in each of the large tanks exceeds 125 square meters.  The smaller tanks each have 46 square meters available. The tank standpipe is fitted with a 100-micron banjo screen which is taken out the day after the larvae are settled. The settlement racks sit off the tank bottom on an aeration manifold made of PVC pipe.

Two layers of shade cloth, 85%, are fitted to each tank and a third shade is available for the initial settlement phase.

Management of nursing phase:

Nursing tanks are filled with the filtered water 3-5 days before the introduction of larvae from the hatchery and a slow flow is maintained over the settlement racks.  This practice allows a bacterial coating, the first food of the abalone, to be established on the corrugated sheets. Abalone larvae are settled into the tanks and distribute themselves onto the corrugated sheets.

Diatoms of 10 microns are inoculated into the tanks the day after settlement of the abalone larvae.

Tanks are left uncovered for several days until the diatoms are established and then the tanks are shaded with the three layers to slow further diatom growth.

Spat-diatom ratio: Once the settled spats are seen grazing on the diatoms, one of the three shades is removed to encourage the growth of diatoms. The same process is repeated depending on the spat-diatom ratio. Diatom growth is strictly regulated so as not to overgrow the abalone while at the same time keeping sufficient diatoms available as the juveniles graze. 

Supplemental food: Diatoms growing on the corrugated sheets can be supplemented in the later stages with the addition of dried diatom powder, artificial abalone feed wafers and with wild Ulva sp. that grows in the tanks.  About two months before harvest the juveniles are introduced to macroalgae which may include Ulva, Palmaria, or Gracilaria sp.

Note: I have been told that one kg of diatom was found sufficient for the production of the 120,000 spat. In fact, one kg of live diatom (Navicula incerta) was purchased from a commercial producer and used to inoculate two newly settled tanks as well as being used to inoculate an unsettled tank.   Diatoms were later harvested from this tank for further inoculations in later settlements.

Collecting grown spats: When the spats are ready for farming, they are collected and graded. During the visit, there were four graders. The largest size could reach about 1-g while the smallest can be 0.25g

Note: The largest spat seen during the visit was introduced in the nursery facility six months before and will be ready for farming about three-four months after the visit.

Sampling: Settled juveniles are counted when they become visible so that populations can be adjusted as necessary.  Periodic length measurements are taken to check the rate of growth.

Settlement success: The ratio between the larvae and produced spats can vary from year to year and from tank to tank.  Temperature, genetics, tank management and diatom diet all factors contributing to survival. This nursery operation plans on 2% survival which gives sufficient grazing surface per animal until they reach a size that they can be weaned onto macro seaweeds.  Survival at greater than 2%, if not dealt with by early population reduction, will lead to overcrowding and reduced growth rate.

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