Fishing

4 Factors Influencing Fishing

These four physical and socioeconomic impacts influence the success of fishing.

• Presence of fishing grounds: fish rely on plankton as a source of food. For an area of ocean to support a plankton population, it must be shallow enough to allow sunlight penetration and be near upwellings to receive an adequate mineral supply.

• Coastline configuration: indented or irregular coastlines provide high-quality breeding sites for fish. The fish are sheltered from strong winds and ocean currents, and remain undisturbed by ships and other human coastline activities.

• Capital: fishing requires capital to purchase gear, vessels, refrigeration systems, and afford new technologies.

• Market: fishing industries will be most successful in areas with large populations, enabling a steady market.

Benefits of Fishing on the Human Environment

Approximately one billion people around the world rely on fish as their primary source of protein. As a result, fishing provides an income for millions.

Furthermore, seafood is often considered a superfood, packed full of essential nutrients and minerals:

• Protein enables tissue growth and repair

• Seafood is low in saturated fat (which raises 'bad' cholesterol, increasing the risk of heart attacks and strokes)

• Iron is used to make haemoglobin in red blood cells, which transport oxygen around the body

• Vitamin D regulates calcium and phosphate to keep bones healthy

• Omega-3 reduces the risk of cardiovascular disease and heart attacks

• Docosahexaenoic acid (DHA) plays an important role in brain development, improves memory and focus.

Different Types of Commercial Fishing Methods

What is commercial fishing?

Commercial fishing differs from subsistence fishing – where individuals fish at a small scale for personal or family consumption.

Large-scale commercial fishing is unsustainable. It damages the environment, leads to overexploitation, and generates bycatch.

This table summarises the main commercial fishing methods, their energy usage, catch selectivity, and their negative environmental impacts.

Negative Effects of Fishing on the Environment

Large-scale commercial fisheries negatively affect the environment.

Overfishing

Many fish species are being removed faster than they can replenish their population, leading to population decline. Approximately 34% of the world's fish stocks are being overfished.

Changed Age Structure

Commerical fishing has influenced the age structure of fish populations. Fishing targets larger individuals because they provide more food. Larger individuals are older, thus mature and able to reproduce.

Removing larger fish may limit reproduction, leading to population decline.

Alternatively, it may act as a selection pressure on the remaining population. Smaller individuals are not targeted by fisheries, so they are more likely to survive and reproduce than larger individuals. So, fishing could actually trigger a fish species to evolve a smaller body size!

Bycatch

Approximately 40% of the world's catch is bycatch, so it's a major issue.

Bycatch contributes to overfishing and declining populations. Other animals, such as sea turtles and marine mammals, are also affected.

Bycatch also causes economic problems for fisheries and their consumers.

Ghost Fishing

Abandoned fishing gear, such as nets and traps, is one of the main sources of debris impacting the oceans.

The gear traps animals, entangles and endangers marine life, and affects habitats.

Habitat Damage

Commercial fishing – in particular, demersal fishing methods – can damage benthic environments.

Benthic habitats are at high risk of damage from commercial fishing activities.

• Seabeds: trawling erodes the sea floor, disrupts habitats, and may impact the ability of the ocean to absorb carbon.

• Coral reefs: these biodiverse ecosystems are an excellent food sources for millions around the world. However, destructive fishing methods (such as trawling and the use of explosives) can damage corals, altering habitat structure and reducing diversity.

• Seagrass beds: these ecosystems are used as breeding grounds for many fish species. Destructive fishing methods can damage the habitats.

Impacts on the Food Web

Targeting a particular species can have knock-on effects on the marine food web.

Removing a prey species may result in a decline of predators due to decreased food availability.

Alternatively, removing a predator species could result in an abundance of herbivorous prey, who overexploit important plant species.

It's not just fish who are affected – marine mammals may experience removal of their preferred prey, and the consequences of habitat damage.

Fish Population and Maximum Sustainable Yield

To understand population ecology, let's quickly learn a new term.

Fishing and Population Ecology

How can unsustainable fishing affect a population?

Increased mortality, combined with decreased growth and recruitment, lead to population decline.

Maximum Sustainable Yield and Population Size

Fisheries aim to maintain the fish stock at their maximum sustainable yield (MSY).

The MSY keeps the fish stock at the level that produces maximum growth. It's around half of the carrying capacity of the population.

If individuals are constantly harvested from a population at a greater rate than the MSY, the population will decline into extinction.

Population Data

Fish populations are regularly analysed to ensure that overfishing is not taking place.

Commercial Catch Data

• Catch size: the number of individuals harvested

• Catch per fishing effort: an indirect measurement of the abundance of a target species

• Mean fish size: the average size of the catch

• Mean age: the average age of the catch

Biological Research Data

• Breeding success: data sources include egg viability, larvae density, and recruitment rates

Importance of Fish Conservation

Fish populations are declining due to overfishing. As a result, it's important to conserve these populations to minimise ecosystem disruption and ensure an adequate food supply. How can fish be conserved?

Catch quotas set limits on the catch size, thus limiting the number of fish that can be harvested from a stock.

Net design, which includes:

• A small mesh size to limit entanglement

• Escape panels for small fish to escape

• Acoustic deterrent devices (e.g. dolphin pingers) to scare away marine mammals

Alternative fishing methods, such as rod-and-reel and spearfishing, limit the number of individuals who can be caught at a time.

Restriction of fishing efforts limits when and where fishing can take place. They include:

• Marine Protected Areas, which put legal restrictions on fishing in certain locations

• No-take zones, which can be established during breeding seasons

Minimum catch sizes prevent immature fish from being harvested, allowing fish recruitment and reproduction to take place.

Captive rearing and release programmes can be used to boost wild populations of threatened fish species.

Reducing ghost fishing, which includes:

• Biodegradable equipment

• Using radio-tracking to prevent abandonment, make lost gear easier to recover, and make it easier to hold those who discarded it more accountable

Positive Impacts of Sustainable Fishing on the Environment

How does sustainable fishing benefit the environment?

• Protects marine fauna: sustainable doesn't disturb the population structure, preventing declining birth rates and extinction.

• Selective methods and waste reduction: sustainable fishing methods minimise bycatch and unnecessary waste. If there is any bycatch, it's used to make fishmeal to prevent waste.

• Reduces pollution: sustainable fishing methods produce less waste, consume less energy, and don't use harmful chemicals.

I hope that this article has explained fishing for you. It's a significant food source for millions, but commercial fishing activities affect the environment and harvest fish unsustainably. Understanding sustainable yields and population ecology can help us conserve fish stocks.

^{1. Jane Marsh, The Pros and Cons of the Commercial Fishing Industry, Environment, 2020}

^{2. Joanne Bradbury, Docosahexaenoic Acid (DHA): An Ancient Nutrient for the Modern Human Brain, Nutrients, 2011}

^{3. Lawrence C. Hamilton, Outport adaptations: Social indicators through Newfoundland's Cod crisis, Human Ecology Review, 2001}

^{4. National Geographic, Sustainable Fishing, 2022}

^{5. WWF, Supporting sustainable fishing practices, 2022}

^{6. WWF, Working on seafood: The Blue Food, 2022}