Pharmaq

Mowi’s Paul Fletcher assesses Pharmaq’s SmoltVision

Vision for smolt

IN an interview with Fish Farmer, Paul Fletcher, manager at Mowi’s Lochailort hatchery, shares his views on SmoltVision, the new tool from Pharmaq Analytiq designed to help managers assess the readiness of their smolts for transfer to seawater.

Fish Farmer: How long have you been working at Lochailort? Paul Fletcher: I have been working at Lochailort for just over 11 years, five at the old site here and the rest at the new unit.

FF: And roughly how many fish are taken through to the smolt stage at the site? PF: We smolt approximately five million fish per year here at Lochailort. FF: Historically, what methods have you used to assess your stock’s readiness for transfer to sea water? PF: The way we have assessed the readiness of the stocks is normally through ATPase sampling which is done through our own labs. Blood chlorides are also sometimes taken.

FF: It has been said that assessing readiness for transfer to seawater is more challenging in fish raised in recirculating aquaculture systems (RAS) than those reared in flow through or freshwater loch systems. What is your view on this? PF: It certainly can be more of a challenge to get the timing just right to transfer the smolts from a RAS system; over the years we have seen the smolting process become quicker, with us now looking at the fish to be smolted around 300350 days, whereas at the freshwater loch sites we seem to be steadily achieving this at 400450 days. We are trying to hit a small window where all the fish are at their optimal transfer point simultaneously to ensure a good transfer with very little mortality, and where the fish can take off in their new environment at sea.

FF: You have recently tried out Pharmaq Analytiq’s SmoltVision tool to assist you in your assessment of your stock’s fitness for transfer. Can you tell us a little about how this works? PF: SmoltVision basically monitors the ATPase activity of two ion pumps (pump in/pump out) located in the gill lamellae. As smolts transition from a life in freshwater to one in the sea they must switch from actively taking ions in from the environment to actively excreting them out. This active process is mediated by ATPase, for which there is a freshwater isoform in the first instance and a seawater one in the second.

By testing 20 fish over three points in time, the shift from freshwater ATPase activity (inward pumping) to seawater ATPase activity (outward pumping) can be monitored. Because the measurement is actually done at the gene

level, this provides a pre-warning of a functional shift in ion pump activity several days in advance of it happening. In addition to this, Pharmaq Analytiq is able to monitor a supplementary marker which it refers to as ‘the co-factor. This can provide useful information about the presence of potentially damaging influences on the gills, including suboptimal water quality, pathogens or simply mechanical damage, all of which can interfere with the normal smoltification process. By tracking the levels of the three markers at three time points in the smoltification period, SmoltVision helps me decide, in advance, the optimum time to transfer my fish – a decision which, I am acutely aware, fish have evolved to make themselves!

FF: Given that the analysis is conducted in Norway, this must affect the speed with which you get the results? PF: The samples are back normally within four to five days from the date sent.

FF: Since using SmoltVision have you noticed a benefit ? PF: Pharmaq Analytiq certainly helps by putting the results across in a way that are clear and easy to understand, giving us the confidence to transfer the fish within the optimal window for the population.

FF: How easy is SmoltVision to use? PF: It is very easy. You sample the gills like you would for a normal PCR gill test, except that you don’t have to use sterile technique, so it is much quicker and less hassle. You then put the tissue in sampling tubes provided by Analytiq, fill out the forms, and send them back to Bergen for analysis. No need to use dry ice, as the samples are stable enough to ship with only regular cool packs. When the samples are analysed we receive an email notifying us that the test is complete, and that we can access the results online on the confidential Pharmaq Analytiq customer portal.

FF: And how do you interpret the results? PF: We don’t have to. Pharmaq Analytiq sends through reports from each of the three sampling points. The interpretation of SmoltVision results differs a little from how the results from a regular ATPase analysis are interpreted. Instead of focusing on the specific numerical value for each fish, SmoltVision focuses on the ratio between the seawater and the freshwater ATPase level. This means that it is not the specific number for each component that is important, but instead the level of seawater ATPase compared to the level of freshwater ATPase. As long as an individual is showing more seawater ATPase than freshwater ATPase, then it is considered seawater tolerant. The results from the analysis are summarised in the report, with a comment describing how many seawater tolerant individuals there are in each sampling point.

FF: Do you anticipate using SmoltVison at Lochailort again? PF: Yes we will be using the SmoltVision testing again and I know other sites will also be using the test.

“SmoltVision helps me decide, in advance, the optimum time to transfer fish” my

Opposite: Talking smoltification. From left to right: Hugh McGinley, freshwater production manager, Mowi Ireland; Paul Fletcher, Lochailort manager Mowi Scotland; and Elise Hjelle, Pharmaq Analytiq. Above: Tracking seawater tolerance: the figure shows data from a single tank of fish with four sampling points in the period 21.01.19 – 15.02.19. Each sampling point involves 20 fish. The yellow field indicates the level of seawater ATPase expressed at each sampling point, and which increases over the sampling period. Once the group has crossed the smolt threshold the fish are considered seawater tolerant. The co-factor is within the normal level of expression, and is thus not indicating any disturbance of the smoltification process for the group in question. Below: Differentiation between seawater and freshwater (Picture McCormick et al., 2013a).: These images show immunolocalisation of chloride cells in the gills of wild salmon. The green cells are freshwater type cells and the red cells are seawater ones. The first image shows a fish at the parr stage, adapted to a freshwater environment and producing mainly the freshwater chloride cells (green). After the onset of smoltification, the fish starts to produce more of the seawater type chloride cells (red) as it develops seawater tolerance. Two weeks after transfer, represented in the last picture, the fish has fully adapted to seawater and is only producing the seawater type of chloride cells. During the smoltification process when the ratio between freshwater and seawater cells will vary, it is important to be able to distinguish between the two types, in order to track the progress of the population.