Whilst some may focus on improving catch efficiencies, losses can occur throughout the supply-chain. These ‘post-harvest losses’ are most prevalent in small-scale fisheries, in less wealthy regions of the World. Post-harvest losses aren’t just an economic concern, but also one from the perspective of food security.
On the boat
Post-harvest losses first appear when fishers haul in their catch. Nets or pots left in the water too long may bring up fish that have long since died, reducing their quality, or have been partly/completely eaten by other predators.
Discarding of part or the whole of an animal is common in many fisheries both in developed and developing nations. Fishers may not be allowed to land individuals below a certain size, or species that they do not own quota for. In individual quota situations where fishers are allocated a portion of the total quota, selecting for the most valuable fish (high-grading) can exacerbate discard rates.
Where only part of the animal has market value, fishers may simply remove the piece they want, discarding the rest. Shark finning is among the most controversial discarding practices of this nature.
Finding markets for edible species that are not commonly consumed remains a global issue for fisheries in developed and developing nations.
Whilst discarding of edible fish may be significantly lower in subsistence/small-scale ‘artisanal’ fisheries than for more industrial operations, losses from storage and preservation may play a greater role.
Fish are susceptible to spoilage, particularly through exposure to high temperature, or even physical damage from people working on the boat if they are not sufficiently contained.
Refrigerated storage is widely used on industrial fishing boats that spend many months at sea, but for artisanal fishers, both cost and space on board the vessel may block such measures. However, even cool-boxes filled with ice, alongside the rapid gutting and storage of fish can help reduce degradation in quality of the fish.
Other options include slowing down spoilage by, for example, keeping the fish covered with cloth, out of direct sunlight, and regularly pouring seawater onto the covering to cool the fish.
Problems with insufficient storage and preservation can continue once the fish has been landed. Fish may be sold direct to consumers or to processors at markets or direct from the landing site. During marketing and subsequent processing and storage, there may be losses both in terms of quality (reducing the value of the product) as well as physical losses such as through predation from other animals, and fragmentation through poor handling and transport.
As on the boat, storage – ideally cold – is desirable but not always obtainable. Shade remains important, but other measures such as keeping the fish off the ground can help reduce contamination that may spoil or reduce the quality of the fish. Infestation from pests can be a particular problem.
Blowflies are a common pest in most parts of the world, and can easily contaminate accessible fish with eggs both at market and at the processing stage. Once hatched, the larvae eat the flesh of the fish, resulting in physical as well as quality loss. The use of insecticides on fish to reduce contamination is widely reported. Whilst some insecticides are considered safe for human food, others are not. In addition, concerns about overuse of food-safe insecticides in some areas such as Bangladesh have been raised.
Work by fisheries consultant Nancy Gitonga in Kenya suggests that salting before curing could significantly reduce the number of blowfly laying eggs in the fish, though other studies such as those from John Esser, formally based at University of Lincoln, suggests that success can be highly variable. Blowfly may prefer unsalted fish, but where there is no alternative, salted for some blowfly species can work just as well.
Mould is another shore-based issue, but one that more often occurs during processing, storage, or transportation, typically when fish are not properly dried, or where packaging allows damp to get into the fish. Poor/unhygienic packaging (and indeed handling) can also introduce other contaminants such as bacteria that may not just reduce the quality of the fish but make it hazardous for consumption.
Whilst solutions to the sorts of causes of post-harvest losses listed here may seem simple for developed nations, it is worth remembering that for developing nations cost can be extremely prohibitive. Ice, for example, can be extremely expensive, and in places where there is no electricity, may not even be possible to obtain.
Other solutions may simply not be cost-efficient-they do not guarantee a sufficient increase in value for the cost of implementation. In addition there can be a failure to get the right information to those working in the industry to help them reduce losses, or indeed a lack of resources to help them assess and implement solutions.