The use of ice on small fishing vessels
By
Michael Shawyer and Avilio F. Medina Pizzali
Food and Agriculture Organization of the United Nations
Introduction
All species of fish, when properly chilled, will stay fresh for longer periods than those that are not preserved in any way. The use of chilling techniques such as ice, therefore, effectively prolongs the length of time available for fishing trips and makes it possible to increase the catch with economic benefits for the vessel and crew. Products brought to market in a well-preserved condition will generally command higher prices, both at wholesale and retail levels, and thus give better returns to the fishing operation.
Given the above, it might be assumed that all types and sizes of fishing vessels would benefit from the use of ice for catch preservation. However, in practice there are limitations. On the smallest types of vessels, such as small rafts and the smallest dugout canoes, there is no space to keep ice until it is needed. However this may not be a problem as the fishery undertaken by these very small craft usually only lasts a few hours and fish is consumed or sold on a daily basis. In some of these very small fishing craft, owners are aware of the problems of catch deterioration and often use wet sacking or palm leaves to cover the catch, lower the temperature and so reduce spoilage.
Many larger vessels capable of spending a day or more in fishing operations will benefit from the use of some form of on-board preservation, such as ice or chilled seawater (CSW). This category might include artisanal fishing vessels, such as larger dugout canoes, outboard-motor-powered launches and larger inboard- engine-powered vessels up to 20 m long.
With increasing demand for good-quality fresh fish, globalization of the market for these products and increasing awareness of fishermen, the use of ice on board boats is growing. Increase in the use of ice creates a need to ensure that it is used efficiently. Ice production consumes a lot of energy, so unnecessary waste is to be avoided. The most economic way of reducing this waste on board fishing vessels is by using proper storage, such as adequately insulated ice boxes, containers and fish holds where ice is stored and used to preserve the catch.
On small boats portable insulated boxes made of various materials are often used to carry ice to the fishing grounds. Ice is then transferred to the catch in suitable ratios until either all the ice is used, or there is no more space aboard for more fish.
Larger boats are able to carry more ice, which allows them to make longer fishing trips, generally with better economic returns for the vessel and crew.
With advances in refrigeration, in particular the advent of compact and relatively lightweight ice-making machines suitable for on-board installation, it is now possible to install ice machines of various types on quite small vessels. This gives a certain measure of independence in fishing operations where trip length is no longer limited by the quantity of ice loaded in port or by how long it will last in the ice hold.
The beneficial effects of using ice can be apparent for a wide range of fishery activities, both small and large scale, and for virtually all species. Ice raises both the quality, and thus the value, of practically all species of fish. This promotes sustainable use of these renewable resources because the harvesting sector is able to preserve catches for longer periods and therefore reduce post-harvest losses.
Contents
1 – Introduction
- Chilling versus freezing of fish
- The preservative effects of chilling fish
- Factors affecting the rate of spoilage in fish
- Shelf-life of fish in ice
2 – The manufacture of ice
- Sea or freshwater
- Types of ice and how they are made
- Refrigerants and their environmental impact
- Safety observations
3 – Planning considerations for ice plants
- planning the requirements
- Storage of ice on shore
- Handling of ice
4 – The use of ice and chilled seawater on fishing vessels
- Initial capture and immediate handling on board
- Fish storage considering type of ice used
- Workability of ice over time
- Quantities of ice required on board
5 – Thermal insulation materials, technical characteristics and selection criteria
- Heat transmission modes and technical terms
- Why insulation is necessary
- Thermal insulation materials
- Types of protective lining for fish holds and selection of insulation materials
6 – Containers and fish holds
- Design of insulated boxes and containers for canoes and small fishing vessels
- Insulated fish containers
- Fish hold design
7 – Calculations and examples for insulated containers and fish hold
- Calculating the specific ice melting rate for an insulated container or fish hold
- Methodology for the calculation of ice requirements for cooling fresh fish
- Calculating gross fish hold volume
- Losses of fish hold volume on installing insulation
- Fish hold volume losses with penboards, shelving and/or boxes
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