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Oyster Grading – Hard graft

Oyster grading – Well that was hard graft!

This past weekend we decided it was time to take a break from building the farm infrastructure and catch up on some actual oyster farming. The plan was to grade last year’s Pacific oysters and move them into their final grow out baskets.

We graded these oysters back in April but between then and now we have experienced an incredibly warm summer. It started poorly, and although it was not like anything experienced further south, from mid May until mid August we have had a terrific summer.

As a result, the oysters have had a serious growth spurt, we were thinking of leaving the oysters as-is until the Spring but this is now not an option. They have grown so much that the baskets are fit to burst and so to ensure we do not stress the oysters, which can lead to mortality, and maintain good shape properties we have brought this activity forward to this autumn.

This turned out to be two very long and hard days, and to use a horrible business cliché it turned out to be what is called a ‘learning experience’.

This was the first time we have carried out a major grading on stock that is more than half grown and we learned that it is not the same type of effort as grading similar numbers of smaller stock as we did in the Spring. The key difference that comes into the play is simply the weight issue, the half grown stock is so much heavier and this has a huge impact on operations.

As this is a largely a manual activity all the baskets need to be manhandled at each stage of the process and with each weighing it at somewhere between 5 and 10 kg this is a lot of weight to be shifting. This was the hard graft bit.

Our plan was to conduct a two day oyster grading effort. On the first day we would retrieve the baskets to be graded and then run as many as possible through the grading plant. On the second day we would finish the grading and return the baskets to the lines. This would enable us to split the effort over two days and work with the tides to minimise the amount of time the oysters were out of the water.

The first unforced error we made was taking too many baskets ashore for the time window we had available to grade, as we just did not have enough time to run them all. As a result, we had to return about 30% of the baskets we took ashore to the lines untouched, and this obviously involved a lot of extra effort and time.

When running the grading plant, it also became apparent that the bigger oysters took longer to run. There was actually a twofold loss of efficiency as compared to smaller seed. Firstly, the larger seed take more time to feed into the grader, you can not just fill the machine as fast as possible as it shall not work properly. Secondly, the bigger oysters fill the output collectors more quickly, and this in combination with the lower filling density of the output baskets means it is much more time consuming to fill the new baskets.

The management of baskets on shore was also an issue. As mentioned previously the input baskets are very heavy and the output baskets are more numerous, and this means there is a lot of manual handling required moving these items between the boat and grader and vice versa. As a result, this means time is lost and the workers get tired quite quickly!

Finally, we had to redeploy all the oysters back out onto the lines and this was also a challenge due to the tight tidal window and the fact that each input basket had turned into three output baskets. We had to do three full runs with the boat and even although we were working at full steam, by the time we got the last basket on the lines the sea was pouring in and was waist deep. A close call.

So some crucial lessons for us of the type that you can only learn by doing. Firstly, when dealing with larger stock we need to break the activity down into smaller more manageable work units. Secondly, we need to make better use of our shore facilities, we need to make a platform we can fit to the boat trolley so we can use the winch to move baskets up and down the slipway and so save time and our backs. Finally, we have been using a supplementary pontoon to help move baskets in and out from site but this has not proved to be as successful as we had hoped and needs to be replaced with something with more capacity; in this way we can then reduce the number of boat journeys and free up time which shall be invaluable when it comes to deploying the baskets.

The oyster grading itself went well. As touched upon above, growth this year has been terrific and the stock is in great condition and the BST baskets are obviously doing a great job of tumbling the oysters creating good shapes and deep cups. We were delighted to observe very few mortalities within the stock, we have not crunched the numbers yet but it shall definitely be less than 5%.

In fact we culled more healthy oysters than there were dead ones. These culled oysters were doubles where the shells have been fused heavily together and can not be separated. We noticed when the seed initially went in that this batch had more of these than normal and despite effort to separate them at that point a few had made it through to this point. It is a shame as there is nothing actually wrong with these oysters but they are not fit to be sold as individuals on the half shell. The bonus was a free feed for the workers!

All in all, a really busy and at times a somewhat stressful experience. That is not to say it was not a success, it was. As well as learning that we need to adapt our approach we have now also graded 50% of the 2017 Pacific oyster stock for the final time. They are now ready for the final grow out and all being well shall be ready for sale from next summer which a great boost.

Now for the other 50%…..

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    Cuairt suas! - Maorach Beag
    21st August 2019 at 4:20 pm

    […] Hard graft […]

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