Overfishing harms Aotearoa’s marine ecosystems by depleting fish stocks, disrupting food chains, destroying habitats, and affecting local communities and economies. Sustainable fishing practices are essential to protect the ocean’s health.

Depletion of Fish Populations Overfishing reduces fish populations faster than they can reproduce, leading to a decline in important species like snapper, hoki, and pāua. This disrupts the balance of marine ecosystems and affects the entire food chain.

Ecosystem Imbalance When certain fish species are overfished, it causes an imbalance in the ecosystem. For example, predators may struggle to find enough food, and prey species may grow uncontrollably, disrupting the natural harmony of the ocean environment.

Bycatch of Non-Target Species Overfishing often results in bycatch, where non-target species like dolphins, seabirds, and turtles are accidentally caught in fishing gear. This can lead to declines in these species and further harm to marine biodiversity.

Impact on Local Economies and Communities Overfishing can reduce the availability of fish stocks for commercial and recreational fishing, affecting the livelihoods of those who rely on the ocean for their income. This includes Māori communities who depend on the ocean for traditional fishing practices.

Overfishing can reduce the availability of fish stocks for commercial and recreational fishing, affecting the livelihoods of those who rely on the ocean for their income. This includes Māori communities who depend on the ocean for traditional fishing practices.

Undaria (Asian Kelp): Undaria pinnatifida, or Asian kelp, is an invasive seaweed from Asia that grows rapidly, forming dense underwater forests. It competes with native seaweeds for space and light, reducing habitats for species like pāua, kina, and fish. It alters marine ecosystems, making it difficult for native species to survive.

Northern Pacific Seastar: The Northern Pacific seastar (Asterias amurensis) is a large invasive starfish introduced to New Zealand through ship ballast water. It preys on shellfish like mussels and clams, causing their populations to decline. This disrupts local food chains and outcompetes native starfish and other bottom-dwelling species, further harming the marine ecosystem.

Asian Date Mussel: The Asian date mussel (Musculista senhousia) is an invasive species that spreads quickly and attaches in large numbers to the ocean floor. It outcompetes native mussels by forming dense mats, reducing space and resources for other marine life. It disrupts ecosystems by altering the seabed’s structure, affecting sediment and nutrient flow, and degrading habitats for species like fish, shellfish, and seabirds

European Green Crab: The European green crab (Carcinus maenas) is an invasive predator introduced via ship ballast water. It preys on native shellfish like pāua, mussels, and cockles, reducing their populations. The crab also outcompetes native crabs and other small marine species for food and habitat, and damages vital habitats like eelgrass beds, which are important for fish breeding and marine biodiversity.

Plastic Pollution Plastic waste, enters the ocean from land-based sources and littering. Marine animals can mistake plastics for food, leading to ingestion and suffocation. This often causes injury or death. Microplastics in the Food Chain: Small plastic particles, or microplastics, are ingested by plankton, fish, and shellfish, contaminating the food chain. These plastics eventually make their way into human diets when seafood is consumed.

Chemical Pollution: Agricultural Runoff: Fertilisers and pesticides from farms can wash into rivers and oceans, leading to nutrient overloads in coastal waters. This can cause harmful algal blooms, which deplete oxygen levels in the water (eutrophication), suffocating marine life and damaging habitats like coral reefs and seagrass beds. Impact: Species such as fish and shellfish can suffer from low oxygen environments, disrupting ecosystems and fisheries. Heavy Metals and Toxins: Industrial waste and mining activities release toxic substances, including heavy metals like mercury and lead, into the ocean. These substances accumulate in marine species, especially larger fish, making them unsafe for human consumption and causing long-term harm to marine ecosystems.

Marine Debris Ghost Fishing Gear: Lost or abandoned fishing gear, such as nets and lines, continues to trap marine life, a phenomenon known as “ghost fishing.” This can entangle and kill fish, turtles, dolphins, and seabirds, further endangering already threatened species.

Climate change is affecting Aotearoa’s oceans by warming sea temperatures, increasing acidification, and causing sea levels to rise. These changes threaten marine ecosystems, species, and industries, making it crucial to protect and manage marine environments more sustainably.

Sea Level Rise As global temperatures increase, polar ice melts and sea levels rise, which can lead to coastal erosion and the loss of critical habitats like estuaries, mangroves, and wetlands. Rising sea levels also pose a threat to coastal communities, infrastructure, and ecosystems, increasing the risk of flooding and storm surges.

Impact on Marine Species Coral reefs and kelp forests, which provide habitat for many marine species, are also threatened by temperature increases and acidification. Species like New Zealand’s unique seabirds, dolphins (like Māui and Hector’s dolphins), and penguins are particularly vulnerable to changing ocean conditions. Warmer seas and habitat shifts can affect breeding, feeding, and migration patterns.

Ocean Acidification: Increased carbon dioxide (CO₂) in the atmosphere is absorbed by the ocean, making the water more acidic. This affects the ability of marine organisms like shellfish, corals, and plankton to form shells and skeletons, which weakens their survival. Acidification threatens New Zealand’s aquaculture industry, which relies on species like mussels, oysters, and other shellfish.