Refrigerated Sea Water Evaluation                    See Video

January 2008

Acknowledgements

A number of government officials as well as fishing industry representatives assisted in the completion of this project. Funding for this project was provided by the Government of Newfoundland and Labrador, Department of Fisheries and Aquaculture. Thanks are expressed to North Atlantic Cold Company Ltd., the Fish, Food and Allied Workers Union, Atlantic Hydraulic and Machine Ltd, and Joe Brake and crew of the fishing vessel Kara and Karen.

Background

Fish quality is of great importance to fish harvesters, processors and consumers. It has been the goal of the fishing industry for many years to continually increase the landed quality, and the quality of processed fish. Refrigerated Sea Water (RSW) systems have been known to increase product quality, allow increased trip times and distances, and reduce product loss. But small scale systems for inshore vessels have not been practical, due to the size and cost of the units. The unit used for this project has just been introduced to the market (March 2007) after years of development by the manufacturer, costs substantially less than other units, takes up much less space, and is portable.

Introduction

This project involved the purchase of a newly designed small-scale Refrigerated Sea Water (RSW) unit designed for boats ranging in size from 25-45 ft. Department representatives viewed the North Atlantic Cold Company (NACC) unit at the International Boston Seafood Show in March, 2007. The information distributed at the seafood show indicated that this unit could chill, aerate and re-circulate 1000 litres of seawater, and keep harvested species alive on the vessel until delivery to the dockside. It was apparent that this unit could potentially solve some issues of quality related to several currently harvested fish species, including Snow Crab, Lobster, Cod, and pelagics such as herring  and mackerel. Transport of fish to the processor in mid-summer while keeping the product at the required temperature means keeping an adequate supply of ice on the vessel from the time of departure to return to the dockside, sometimes a difficult task when summertime surface water temperatures can reach 20ºC, and air temperatures are up to 30ºC. The quality advantages of live delivery are clear, especially in shellfish, but also to finfish such as cod, where premium quality product can be marketed at a higher price. The Department carried out an evaluation of its usefulness in bringing superior quality product to the processing plant, especially in warm weather conditions, and where ice is difficult to obtain or use. The budget for the project, including purchase of the unit ($10,000.00 USD), was $22,300.00. Funding for this project was provided by the Government of Newfoundland and Labrador, Department of Fisheries and Aquaculture

Objective

The objective of this project was to complete an initial proof of concept trial. We undertook a one day experiment to shoe that the unit operated correctly, could keep cod fish alive in an insulated fish tub, and allow transport of live fish to the dockside.

Project Methodology

The RSW unit was purchased in June 2007, and Atlantic Hydraulic and Machine Ltd. was contracted to complete the setup of the unit. The RSW unit was bolted to a Seaplast 335 1000 Litre insulated tub, and all electrical, hydraulic and water lines were installed. The resulting unit measured approximately 2 m long, 1.5 m high, weighing approx. 250 kg. This unit can be easily lifted by most dock cranes and lowered on to the deck of a fishing vessel. Through the cooperation of the FFAW, Joe Brake of Trout River agreed to provide his vessel, the Kara and Karen for the trials.

Figure 1. The Kara and Karen at the dockside in Trout River

Once the unit was installed on the deck of the vessel on October 2, the hydraulic and electrical lines were connected and the unit was run for approximately one hour at the dockside to ensure it operated correctly. The designer of the unit, Larry Vallée of NACC traveled to Trout River to offer advice on installation and use of the system. Unfortunately, poor weather prevented at-sea trials while Mr. Vallée was in Trout River, and we had to wait for better weather conditions.

Figure 2. Larry Vallée of NACC, ensures the unit is operating correctly.

On October 15, we traveled approximately 8.5 km offshore West of Trout River (Figure 3) and filled the insulated tub with seawater. We caught 17 cod fish using handlines and placed them in the tub for transport to the dock. The water temperature in the tub was monitored every 10 minutes for 1 hour and 40 minutes. A 23 litre bucket of seawater was taken aboard at the start of the project, and monitored for 30 minutes. Throughout the trial, the fish were checked for condition.

Figure 3. Showing the location of the cod sampling site.

Results

At 09:20 on October 15, the air temperature was 6.8 ºC and the surface water temperature was 8.9 ºC. The RSW unit was started at 09:20, and fish were put into the tank at the same time. Of the 17 fish, three had injuries due to hooking either along the side or in the gut. The 14 uninjured fish remained active and in apparently good health throughout the transport to the dockside. The initial temperature of the output water from the chiller was 9.0 ºC. Table 1 shows the temperature of the water in the tub at 10 minute intervals.
 

Table 1. Temperature of the water in the insulated tub

Figure 4. Graph showing the temperature in the RSW unit vs the 23 litre bucket

The temperature of the water in the bucket on deck went from 8.9 ºC to 10.2 ºC in 30 minutes. The results show that with fish placed in the tub, and with no prior chilling of the water, the unit was able to maintain surface temperatures for the nearly two hours of transport time to the dock.

Figure 5. RSW unit and insulated tub on deck of the Kara and Karen. The
cover of the chiller has been removed for access to the internal mechanics.

Discussion

The objective of this project was to show that the RSW unit worked properly and could keep cod fish alive during transport to the dock. The unit performed as hoped, and further discussions with the designer showed how performance could be improved in the future. Running the unit during travel to the fishing grounds would allow water temperatures to drop below surface temperatures and be closer to actual bottom temperatures, making it even better for fish pulled up from colder conditions. Although there is no need to carry ice when using this unit, pre-chilling the water by using 20-30 kg of ice at the time of filling the container would reduce the time required to lower the temperature of the water prior to placing the fish in the tub. Discussions with the designer also showed that, if aeration is not an issue, the unit can be mated to two 1000 litre tubs and it can chill and re-circulate 2000 litres of water, thus allowing more product to be transported.

The fisher told us of past projects where fish were brought from the same area to the dock for tagging studies, and held for transport in un-chilled water. He reported that mortality was high, and the fish died within 15 minutes, either from high temperatures or lack of oxygen. We showed that cod fish lived much longer than this, and appeared to be in good health after the boat returned to the wharf. We suspect that for future studies involving tagging or other fish handling, such as surgical implantation of radio telemetry units, this type of unit would be very helpful in reducing fish mortality during handling and transport.

As an addition to this project, we tested a new bag designed to lift snow crab out of a container. The bag works with a metal frame attached to a crane cable and hooks on the four corners of the bag, lifting the entire catch out at one time, reducing crushing and extra handling.

Figure 6. Showing the crab handling bag in the insulated tub.

The intent was that the bag would allow easy offloading of product from the insulated container and still allow water circulation. Unfortunately, the bag did not fit the Seaplast 335 containers we used for this project. We may have the manufacturer redesign and build an appropriately sized bag for future trials with the RSW system.

Given that the Department has purchased the RSW unit, further testing is planned to more fully explore the capacity of these systems, and the species with which it can be used. Future trials will involve shellfish such as lobster and snow crab, and pelagic species such as herring and mackerel. The pelagic fishery could benefit from this technology in smaller quantities of product destined for higher quality food markets, rather than volume based markets.