Warmer global temperatures have an all-encompassing effect on fish. Fish are ectothermic and the temperature around them regulates their bodily functions; a disrupted temperature affects all parts of the fish life-cycle. Here are 5 major problems facing fish in warmer waters:
Yes, the oceans are warming, and yes the small increase in overall ocean temperature is very significant. NOAA (National Oceanographic and Atmospheric Administration) scientists gathered data between the years 1993 and 2008 and noted a 0.18oC rise in temperature. But it is critical to understand that this level of heat increase is HUGE, when you take into consideration the enormous amount of water on Earth.
“…that little bit of temperature increase represents a lot of heat…the total heat added to the oceans during that 15-year period is equivalent to the energy that would be released by exploding about 2 billion Hiroshima-scale atomic bombs” - John Lyman, NOAA
Our Earth is more than 70% covered by water, so there should be little surprise that climate change will have a vast effect on the creatures that inhabit this watery part of the world. Fish live in specific waters that meet all of their needs for survival- the right temperature, adequate amounts of food and good breeding grounds, and all of this is changing because of rising global temperatures.
Eventually all species will be affected by climate change. But for now, different fish species, in varying regions will face unique effects. The global temperature is rising, and waters, although slow to change temperature, will have enormous effects on marine wildlife. As waters do warm, fish must migrate away from traditional ranges and toward the poles, in an attempt to escape hotter temperatures. Scientists are predicting that fish will change their ranges by more than 40km (25+ miles), each decade (http://www.telegraph.co.uk/earth/earthnews/4604439/Tropical-fish-swimming-north-because-of-global-warming.html). That means in an average lifetime of 80 years, we will witness fish moving over 2,000 miles.
Change in distribution and survival of fish will impact millions of people. Many rely on fish for food, business, local economy and tourism.
This wide-spread migration of fish, towards cooler water will have significant negative effects on people, as fisheries will no longer be able to sustain their traditional fishing stock. One example from scientists at the New England Aquarium,
A loss of cod would be devastating to the Cape Cod ceconomy. And, although some areas will continue to support adult fish, the low survival rate of juvenile cod, will ruin the fish population in a few short years. Here is another example, of a region that is seeing very real consequences of global warming presenting in their local fish populations.
Like the cod, which will migrate north in a search for cooler waters, many other fish will make a similar relocation. However, not all fish have somewhere colder to move towards. The polar region represents a particularly critical environment whose inhabitants depend upon the icy waters. Many of these northern fish simply have nowhere colder to go. The arctic will be among the first places to see a dramatic decrease in native fish species—also negatively affecting the Native peoples that rely on fish as a major part of their diet.
Causes for Concern
Warming temperatures coincide with an increase of more extreme weather events (hurricanes, flooding, droughts etc.). These present significant problems for fish, as vital coastline habitats are destroyed, not only by the increased erosion caused by rising sea levels, but also by strong storms. These rough waters reduce population numbers, especially for Salmon, as their eggs are “scoured” (where quick tides wash the eggs away) from the river-beds http://www.thinksalmon.com/learn/item/what_are_the_impacts_of_flooding_on_salmon1/.
Warmer waters encourage fish to mature at a faster than average pace. This quick maturity results in smaller adult fish, and reduced numbers of offspring in comparison to similar fish living in cooler waters (http://assets.panda.org/downloads/fisherie_web_final.pdf). Lower levels of oxygen will also reduce populations, as fish have to work harder for less amounts of oxygen. With increased temperatures, spawning becomes increasingly difficult for various types of fish. Temperature is a key signal for fish to know when to begin their once in a lifetime journey to spawn. As waters warm, fish must navigate through unusually rough waters, poor quality water and some stream conditions with lower than normal depths. It has also been documented that deviations from current ocean acidity could have profound changes on the survival instincts of many fish.
“Baby fish may become easy meat for predators as the world’s oceans become more acidic. In a series of experiments reported in the latest issue of the Proceedings of the National Academy of Science (PNAS), the team found that as carbon levels rise and ocean water acidifies, the behavior of baby fish changes dramatically – in ways that decrease their chances of survival by 50 to 80 per cent.” - Australian Research Council, Coral Reef Studies
These scientists described young fish, as not having traditional reactions to dangerous situations—viewing predators with curiosity, instead of with instinctual fear.
Warming oceans will have a profound effect on millions of people. In 2008 the US fishing industry made more than $400 billion in global seafood (Food and Agriculture Organization of the United Nations). There are vast economic impacts that will be felt across the country, should fish stocks cease to be so readily available.