Fishing opportunities have long been improved by supplementary releases of hatchery-reared fish such as trout and salmon. The success of the stockings has declined over time creating a need to develop more sustainable methods to replenish declined or even extinct fish populations. The most natural method to re-create a self-sustaining population is to introduce fish eggs to natural reproduction habitats in rivers. Typically this has been done using plastic boxes, which are expensive and difficult to recover from the fast-flowing rapids in rivers.
Now there is a revolutionary new solution for introducing fish eggs to rivers in renewable paperboard boxes that decompose naturally without a need to recover them. The idea was created in 2012 by Manu Vihtonen, an ichthyologist and fish farmer from Finland, who has developed and tested the new boxes during the last two years in cooperation with the packaging manufacturer Pyroll Tampere. The boxes are made from Stora Enso’s CKB multilayer kraft back board, which is durable enough to protect the developing eggs until hatching but decomposes naturally, eliminating the need for the laborious egg box recovery.
Compared with the traditional plastic egg boxes, paperboard is more environmentally friendly, cost-effective and handy to use. The new solution has a significant potential to replace the plastic boxes and increase the use of fertilized fish eggs as a management action to strengthen the declined or even re-introduce the extinct fish stocks.
A 2 dl box can carry 1000-2000 salmon or trout eggs and 95-98% of them will hatch as was confirmed in the trials. Not any box will do but the structure with numerous small holes has to be tailored to various fish species such as trout or salmon. Such a structure is demanding to make as the board has to have a very good stability and any die cutting waste has to be carefully removed, says Pyroll who has protected the design.