Environment & Sustainability
What’s the Biggest Threat to Marine Life?
By Quinn Banning-Arndt, Broadreach HQ
SPOILER ALERT: IT’S US
As the human population grows, the demand on natural resources, such as salt and fresh water fish, increases as well. To keep up with this demand, technological advances have allowed us to find greater numbers of larger fish. The desire is to net the largest species with the biggest individual fish size and as a result of this, we are fishing down the food web. As the numbers of these larger fish populations decrease, we begin to fish smaller species that were not previously sought after. We are systematically reducing the fish populations from the oceans, starting with the biggest fish and working our way down. Because of this, overfishing has the most damaging impact on marine life ecosystems than any other danger they face.
OVERFISHING AND THE FOOD WEB
One of the largest concerns with overfishing is how detrimental it is to the food web and to the fish population size. The number of eggs that a female fish can produce is directly related to their mass, meaning that the larger fish produce more eggs than the smaller ones do. If we remove the largest species with overfishing, we greatly reduce the reproductive potential by eliminating a large percentage of the egg layers which impacts the entire food web dynamic, not just that species. Some of this happens due to by-catches, the nonselective fishing methods that catch everything instead of just specific targets. Species that are caught in these but are not the target species, are still killed but are then discarded. This is a huge waste of life and continues to be a problem despite efforts to reduce by-catching methods.
LINES AND HOOKS AND NETS, OH MY.
Some of the most harmful fishing methods include longlining, gill nets and trawling. Longlining involves setting a main line that has many baited hooks (up to 2,500) attached to it by branched lines or gangions. These lines can be left for days before fisherman return and when they do, they often find unexpected causalities – birds, sharks, marine mammals, and turtles. In an attempt to reduce these unintentional deaths, new regulations call for ‘circle hooks.’ Similar to longlining, gill nets span a long distance but instead of hooks, they consist of a net suspended in the water column. Usually made of monofilament, these nets are invisible underwater and fish swim into them, becoming tangled in the thin threads. Gill nets are a very effective way to catch large numbers of fish. Unfortunately, because the nets are so difficult to detect, other animals often become snared as well. This has caused gill netting to be highly regulated in an attempt to reduce its impact on other aquatic species. Trawling is the only one of the three that requires direct human involvement. Instead of setting up and leaving, this method involves pulling large nets through the water behind a boat. These nets catch everything in their path and therefore had a hugely negative impact due to by-catch.
Seafood is without a doubt a major source of protein for the majority of the human population but current fishing practices are not sustainable due to their many negative impacts on marine and aquatic life. The big question becomes how can we continue fishing without destroying the aquatic ecosystem? Much of this will need to be done at the governmental level through regulations and increased monitoring of fishing businesses. Our communities need to put the emphasis on ‘sustenance fishing,’ fishing designed to provide just what is needed for consumption, and deter large scale fishing operations.
REGULATORS, MOUNT UP.
Another way to help reduce needless loss is to enact catch limits for both companies and individuals. Governments can regulate when, where, and how much fish companies can catch. This has had some success but it is very difficult to effectively enforce these regulations and lobbying from companies often prevent additional regulations from being passed.
In order to protect particular species, regulations have been passed which keep fisherman from catching them year-round and instead limit them to a particular time of year. These seasonal limitations are often structured around spawning, or breeding, seasons, allowing the fish to reproduce and help to maintain their population size. While this can be incredibly affected for a single species, it can be difficult to enforce and not all species breed at the same time. Due to these complications, enforcing a minimum catch size is a much more commonly used regulation. This requires that for a fish to be kept for consumption, it be a certain size, usually determine by species. This helps to ensure that the fish has reached sexual maturity and has therefore reproduced at least once before being killed.
Another approach to relieving the pressure on wild fish populations is the use of aquaculture, also known as aquafarming. This method involves cultivating aquatic populations under controlled conditions and turns them into a ‘crop.’ While this does provide a more stable source of aquatic food, some critics think that the industry causes too much unintentional pollution. Things like excess food, medication (antibiotics and growth hormones), and excrement can escape to pollute the surrounding environment.
At this stage in our society, so much of our food is farmed or produced, very little comes from the ‘wild’. With the steadily increasing size of the human population, the ‘hunter & gatherer’ lifestyle doesn’t suffice on the large scale. Moving forward as a worldwide community, we need to figure out how we will sustainably handle the collection, production and processing of marine life. Continuing as things have been, our oceans and lakes will be depleted long before we satisfy the human need for fish. Whether it is through additional fishing regulations or through advancements in aquaculture, policy needs to keep up if we want to maintain sustainability. Either way, something needs to change or quite soon we could find that we have each dined on our very last fish.
If you’re interested in learning more about marine ecosystems, fish biology and conservation efforts, check out our Caribbean Marine Conservation and Bahamas Marine Biology programs.
To learn about another threat to our oceans and marine life, check out our post on Microplastics and how they’re Turning the Ocean Into Plastic Soup.