How Will Climate Change Impact Fishing?

As our waters warm, seas rise and fish move. Climate change impacts fishing below the surface.

Climate change affects our oceans, particularly sea level rise, which, in turn, affects things below the ocean surface, where the results are harder to see. Aquatic life adapts to these changes. Some species may migrate in search of the environment that best suits them. Other species may become less productive and may even face extinction.

Decreasing populations will impact commercial, sport and recreational fisherman, but most importantly, a vital food supply. Marine and coastal fisheries are a $200 billion industry and support nearly two million jobs; any major changes are concerning.
Climate change impacts the oceans a number of ways. Of paramount importance for sea life is increasing water temperatures.

Troubling Times

In fact, the ocean is warmer today than at any time since record-keeping began in 1880. Water has a high heat capacity. It is believed that the oceans store 90 percent of the excess heat generated by the greenhouse effect. On an even more troubling note,
the rate at which the oceans are warming is also accelerating. This has a harmful effect on aquatic organisms who are sensitive to relatively small variations because water temperatures rarely change.

A graphic outlines how dead zones form in our waters.

In addition to increasing water temperatures, there is more carbon dioxide in the atmosphere that dissolves into the water; seawater is becoming more acidic. This means less calcium carbonate for coral reefs to build, a major factor in the destruction of these reefs. Melting ice caps and glaciers, as well as the physical expansion of water at higher temperatures, have caused sea levels to rise, which certainly affects the spawning areas of many fish species.

Variations in seasonal rainfall and individual storm events cause local changes in water
conditions both in terms of temperature and salinity. The amount of dissolved oxygen water can hold, a critical factor for all underwater life, is a function of temperature. Warm water can’t hold as much oxygen, another negative factor for undersea life. The oxygen-devoid “dead zones” we see in the Gulf and elsewhere will likely intensify and expand, just another way that climate change impacts fishing.

High Temps = High Stakes

Nearer the shore, the stakes are even higher. Many fish, such as red drum and sea trout, use bays and estuaries as breeding grounds. Shrimp, oysters and blue crabs are dependent upon them. Unfortunately, the risk of environmental changes is even greater here. With shallow water, temperature changes are more pronounced and happen more rapidly. Salinity is also significantly affected. Heavy rains will bring an influx of fresh water and lessen salinity.

Drought conditions will diminish freshwater inflow and increase salinity. Pollution, especially nutrient pollution, is a major concern in some areas. In conjunction with warmer water temperatures, this will lead to more harmful algal blooms such as red tide. Stronger storms can produce more damage, and the rise in sea level can dramatically alter habitats.

Even the increase in air temperature can change habitats. For example, along the Texas coast and the Florida east coast, black mangroves are moving northward and replacing
cordgrass marshes. One comprehensive study looked at the predicted geographic distribution of nearly 700 marine species in the Atlantic and the Pacific out to the year 2100 for a number of different climate scenarios. Most, but not all, species shifted poleward, generally following the adjacent coastline.

Many species were forecast to migrate more than 500 miles from current locations because of the higher temperature predictions. A study on the effects of climate change on the Gulf of Mexico fish populations yielded mixed results with some species benefiting and some suffering. Red and gray snapper and red porgy benefited from habitat expansion, whereas, Spanish mackerel were likely to move to deeper, cooler waters. Another study forecast pink shrimp Gulf habitat to decline by 70 percent by 2100. It also predicted that species from the Caribbean may move north into the Gulf.

The Times, They Are A-Changin’

Changes are already taking place. The oyster catch along the Gulf coast of Texas is down significantly. Butterfish are replacing herring in the Gulf. Atlantic cod have decreased by more than a third. Black bass, which concentrated off the North Carolina coast, are now most abundant off New Jersey. The lobster population in the Gulf of Maine has increased dramatically with warmer water temperatures, and blue crabs have also moved in.

Fisheries are among the first industries affected by climate change. Coastal communities feel the brunt of the economic impacts. Fishermen may have to travel much farther to
find the preferred species or just give up on it. Regulations on fishing that worked in the past will become obsolete if not counterproductive. Jurisdictional disputes, even up to
the international level, may result. The increase in ocean temperatures will likely continue, and the effects on sea life may even become more pronounced.

Climate Change Impacts Fishing

The NOAA Fisheries Climate Science Strategy was developed to provide pertinent climate information and predictions to those involved with fisheries so they can prepare to deal with and manage climate changes. In conjunction with Rutgers University, NOAA Fisheries developed the OceanAdapt web-tool to provide easy access to information about the distribution of marine species involved in commercial and recreational fishing over time. Wise management of our ocean resources is our only option. We must keep a constant watch on what is going on under the water’s surface and change policies accordingly.

By Ed Brotak, Southern Boating June 2019

Sea levels are rising across the globe, leading to increased concern for the safety of coastal communities and wildlife populations.

Sea levels are rising as a direct result of the earth’s warming. Due to this warming, the permanent ice sheets over Greenland and Antarctica are melting, which means less sea ice (ice floating in the polar ocean areas) is being formed each winter. Further complicating the matter, the warmer the water the more it expands, which also takes up an increased amount of space. The melting and loss of sea ice has accelerated over the last decade and is now believed to be one of main causes of increasing sea levels. This is irrefutable evidence of global warming, which isn’t limited to one incident but marks a trend of increasing ocean temperatures and levels.

Global average absolute sea level change from 1880 to 2015. Photo: CSIRO / NOAA

According to the National Atmospheric and Oceanic Agency’s (NOAA) State of the Climate Report (ncdc.noaa.gov/sotc), 2015 was the second warmest year on record for the U.S. The report stated that it was “the 19^th consecutive year the annual average temperature exceeded the 20^th century average”. Not only were global temperatures measured at the highest level ever recorded, but they also broke the previous temperature records by an unprecedented margin. And after the data points for 2016 temperatures are finalized, we may find that 2016 was even warmer than 2015. Overall, the earth has been warming since comprehensive temperature records have been kept in 1880, and this warming rate has increased in recent decades. Global warming has been attributed to the actions of humanity, particularly those that have increased the global quantities of greenhouse gases such as carbon dioxide. For example, prior to the Industrial Revolution in the 18^th century, atmospheric carbon dioxide levels were about 280 ppm (parts per million). Today, that level rests at about 400 ppm.

Global warming is an issue for both the Northern and Southern Hemispheres. The Arctic region is facing the harshest increases in temperature. In 2006, NOAA started issuing an annual Arctic Report Card documenting observed weather conditions. The 2016 report is particularly disturbing. The average annual air temperature over land areas was the highest on record with a 6 degrees F increase since 1900, while the Arctic Ocean temperatures were 9 degrees F above average in August. Spring snow cover was at a record low in the North American Arctic, as was sea ice in the fall. On December 22, 2016, a weather buoy just 90 miles south of the North Pole registered a temperature of 32 degrees F, nearly 50 degrees above normal. Even more disturbing, one study suggests that the Greenland ice sheet lost one trillion tons of ice between 2011 and 2014 alone.

There are two ways to accurately measure sea level. Tide gauges have recorded local sea levels for more than a century. However, the old ruler-type gauges are giving way to modern microwave sensor stations. And in the past 20 years, satellite measurements have been available that use laser altimeters. According to NOAA, the sea level has been rising for the last 100 years (corresponding to an increase in the earth’s temperature), and the rate of rise has been increasing in recent decades. Globally, the overall rise in sea level is eight inches, which may not sound like much, so for reference consider that nearly 70 percent of the earth’s surface is covered by water—an estimated 3.5 x 1020 gallons. Also keep in mind that the surface of the ocean isn’t simply flat since the moon’s gravitation causes a significant bulge that moves with the earth’s rotation and causes the tides. Local currents and winds also distort sea level.

Why should we be worried about rising sea levels? About 40 percent of the U.S. population lives in coastal areas, all of which are at risk of flooding. According to NOAA, “Flooding increased on all three U.S. coasts between 300 and 925 percent since the 1960s, with the biggest increases in the Mid-Atlantic.” Naturally, we expect the damaging high tides and storm surges of hurricanes or other coastal storms, but the danger is intensified by higher sea levels, which allow these storm-induced tides to reach further inland and produce even more destruction.

One of the most pressing problems related to rising sea levels is the increased occurrence of “nuisance floods,” which are typically not storm related but rather occur with unusually high astronomical tides. Perigean spring tides or “king tides” occur several times a year when the moon is closest to the earth. Normally, the flooding caused by perigean spring tides is usually minor in low-lying areas and at their worst produce road closures and minor damage. However, in recent years, this tidal flooding has gotten progressively worse and is far beyond just being a nuisance. Roads are frequently becoming submerged under deeper water for increasingly longer periods of time. Homes and businesses have also experienced flooding in their basements. Some king tides rank with major storm tides as the highest on record. South Florida was hit particularly hard by these tides in the fall of 2016.

Wildlife is also severely impacted by rising seas and the resulting loss of coastal habitats. Warmer water temperatures have a negative impact on animal and fish populations that are already adapted to cooler water temperatures. Furthermore, algae blooms occur more frequently in warmer water temperatures, bringing about an increasing number of “red tides”.

What does the future hold? Scientists agree that sea levels will continue to rise as the earth’s temperature rises. Estimates predict that by 2100, sea levels will likely be at least a foot higher than they are today, but this is assuming we don’t have a rapid collapse of the major ice sheets, which could lead to water level rises of 20 to 30 feet.

Is there anything we can do as global citizens to mitigate the impact of global warming? Certainly, we need to cut greenhouse gas emissions around the world, but we also have to prepare for rising sea levels. The infrastructure of coastal cities and communities will need adaptations to prepare for rising sea levels, and ultimately some may need to be abandoned. But rising sea levels impact the entire planet and each of us should take steps to reduce our global footprint. For more information visit arctic.noaa.gov/report-card or climate.gov.

By Ed Brotak, Southern Boating February 2017

Tag: sea level rise