Cultivating Palmaria palmata - Bord Iascaigh Mhara

Nets are attached directly to the header rope in a similar way to the droppers but with multiple attachment points.
To keep a 3-m long net straight and unfolded in the water, a metal or plastic rod should be attached to the
bottom end of the net and 2-3 weights attached.
Timing: The best season for deployment is late autumn/winter. At this time of the year, the growth of Palmaria
will be reduced by the short daylengths and low temperatures but these factors will also inhibit the growth of
opportunistic fast-growing fouling algae. Consequently, the Palmaria will be able to grow sufficiently to develop a
good cover of the string, and this will make it more difficult for fouling organisms to settle when growth conditions
improve at the start of spring in the following year.
Palmaria collectors can also be deployed in late spring/early
summer to exploit the natural period for optimal growth. The
material used for spring deployment should be well developed, i.e.
Palmaria fronds should be at least 1 mm in length, and the culture
string should be densely seeded. This is essential to prevent the
settlement of opportunistic algae which can out-compete Palmaria
plants by very fast growth. Another factor to consider is light. In
summer, light intensities can be very high and small Palmaria
plants can be easily and irreversibly damaged by bleaching (Fig.
6.2). In their natural habitat, this doesn‟t occur because Palmaria
plants are shaded by the canopy of kelp blades. Lowering the
nets or droppers to a greater depth (e.g. 1 m below the surface)
may prevent bleaching over the summer.
6.2 Monitoring of plant development
Biomass increase should be monitored frequently, at least once a month. Fouling algae should be removed from
the header ropes and from the droppers or nets. Depending on the time of deployment and the size of plants
required, the growing season at sea will be between 5 and 8 months (e.g. May to September for spring
deployment, October to April or May for winter deployment). Fronds should be harvested before fouling starts to
affect the quality of the plants.
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Fig. 6.2. Palmaria palmata on a longline in
Strangford Lough in June. The green tips
indicate bleaching by high light. At this stage
affected tissue can still recover.