Human Impacts on Fisheries Resources

Throughout history people have caused themselves problems by not understanding the consequences of their actions.

Many people tend to think of fish species in isolation , but each species is part of a complex ocean ecosystem. There are interactions between fish, plankton, nutrients, water and air, If we don't understand how these interactions work, we can upset the relationships between species or between species and their habitat, So, without meaning to , we upset the balance of oceanic ecosystems.

Fishing
People have been fishing since prehistoric times, for food, for profit, and for leisure, but it is only in the last few decade that there has been serious concern about overfishing, This has been partly caused by a dramatic increase in the world's population and greater international demand for food, fish meal and other marine products.

Both recreational and commercial fishing are now big business, Some commercial boats are large and are capable of staying at sea for months at a time, processing fish as they catch it, Some big boats can process 100 tonnes of fish a day. Fish yields have increased nearly fivefold over the past four decades. The current reported world total marine catch is about 90 - 100 million tonnes. The actual catch could be 30 - 50 percent higher.

At the same time, there has been an improvement in fish- catching technology, especially in deepwater fisheries. Processing , storage, transportation, and marketing systems have also improved, For example, fish finders are now used to locate fish and whole fish can now be packed in ice and sent by plane to arrive fresh or even live in overseas markets.

By-catch
When commercial fishers are targeting a particular species they can also catch other fish species, and sometimes birds and marine mammals. This is known as by-catch. Marine mammals and sea birds are protected under law. Over the last few years the fishing industry has taken steps to minimise unwanted by-catch, for example by designing better nets, blowing hooters to scare seals and making their lines more visible so birds can avoid them.

Reclamations
Land reclamations can destroy nursery grounds of juvenile fish and the habitats of shellfish. Many coastal cities e.g. Wellington, Auckland and Lyttelton, have reclaimed shallow marine areas for extra land. Reclamation is still continuing around New Zealand, but now environmental Impacts Reports are required as part of the consent process. Regional coastal plans are also required to be prepared by regional councils, setting out what activities and effects are allowed in the coastal marine area,, The impact or reclamation on fisheries resources is more likely to be taken into account.

Mineral Exploitation
Oil production, with its associated pollution risks, and mining of the seabed and beach sands can disrupt marine habitats, Mining companies are now much more aware of environmental impacts than in the past.

Pollution
Dealing with waste products is a worldwide problem for both developed and developing countries, Many cities and large industries have often chosen the " out of sight, out of mind" option, discharging sewage and waste products into the sea, Some of the waste products are toxic. In parts of the North Sea, some fish are now so contaminated they're unfit to eat, Some fish are being born deformed.
The problem has not reached that scale in New Zealand, but it is a problem we all need to think about, For example, if you tip house paint down the drain, where will it end up and what damage will it do? If a person tips the remains of pesticides into a stream, what are the likely consequences?