The sea has prevented the world from being affected by climate change by absorbing most of the CO2 that we have released into the air in various ways and a significant amount of heat from the atmosphere. The seas will demand a price for this obligatory duty imposed on them.

Inhabitants of the underwater continue to swim in waters whose conditions are now rapidly changing, and we are only beginning to understand what these changes mean for them. Simply put, fish populations are changing their habitats in response to ever-increasing temperatures and consequent food shortages. As a result, scientists point out that the total fish catch in the whole world may decrease by up to 25% towards the end of the century [link↗]. Since 1970, global sea surface temperature has increased by about 1oF, according to the U.S. Environmental Protection Agency. The ocean is warmer today than ever since record keeping began in 1880 [link ↗].

As water heats up, it tends to hold less oxygen, and its pH drops, making it acidic. So this means that under the sea will be less familiar and colorful in the future.

The number of underwater forests, which are among the most important partners of the seas in protecting the climate, and the coral reefs, which are the most important sources of underwater life, are gradually decreasing and their areas are shrinking. As a result of the decrease in these components, mammals, birds, and even coastal societies, whose regular nutrition depends on the sea, have difficulty in finding the necessary prey / food in the temperature changes experienced.

Coastal people that make a living by fishing are directly linked to the sea they live on in order to maintain their current economy as it is. New effects created by changes in marine ecosystems due to increasing temperatures are inevitable. We have been talking about the decline in the fish species that were caught abundantly until recently from the sea. Although this is not related to climate change alone, it is a result that we can see directly.

For example, the tuna, swordfish and bluefish overflowing from the crates seen in old Istanbul photographs are not seen at all today. In another part of the world, in Alaska, fewer fish are returning to streams and rivers where salmon have been sustainably fished for thousands of years. In the North Pacific, more than one economically valuable crab species is disappearing and commercial hunting of these species is coming to an end. In Alaska, it even canceled snow crab fishing in 2022 as its population was endangered. Dead zones due to prolonged heat waves in the water are more common on the west coast of the USA; therefore, while disrupting fishing activities, it causes more algae blooms. 

Developments are not only about those who are engaged in underwater and water-related economic activities. Hurricanes that accompany climate change-induced superstorms that are stronger than those seen in the past are putting the economic sustainability of fishing communities around the world at risk.

The first thing we have to accept is this: All things that happen due to climate change will only get worse in the future. Today, both air conditioning models that predict how the world will respond to emissions are increasing steadily through 2050. The emission reduction efforts we demonstrate today will be effective in the future. One of the main reasons for this is the thermal inertia in the climate system. So this means that even the heat absorbed long ago continues to warm the planet today.

Despite the recent significant and remarkable climate action with the enactment of the US Inflation Reduction Act, the climatic future is already evident for the next 30 years; it will continue to warm before going into stagnation.

The latest findings from a report by the US State Accountability Office on the management of fisheries in the country are quite remarkable. The report showed that only a quarter of the 46 management plans that identify the fisheries of more than 450 critically important fish stocks in the US alone consider climate change. It draws attention to the conclusion that NOAA Fisheries, the government agency responsible for sustaining ocean fisheries for the benefit of the public, should identify and prioritize opportunities for managers to improve the climate resilience of federal fisheries.

At the bottom line, we need to be open to new approaches, and even ready to put them into practice, to review the way we manage fisheries and change them as needed. In light of decades of evidence-based management approaches, it is necessary to prepare fisheries for climate change to help reduce overfishing, rebuild stocks and restore coastal communities.

We should also keep in mind that since each fishing activity has its own methods and control points, and climate change is not the only impact on fisheries, there is no single solution to adapt our fisheries to the changing climate. Fisheries management authorities will need to review options with tools that can help them predict, model, understand and plan for climate impacts on fisheries.

It is an inevitable fact that if we cannot find a way to improve fisheries in the face of climate change, which is stronger than us, we will be deprived of the blessings of fisheries in the future. Researchers around the world are investing in a better understanding of the changing marine ecosystem and trying to build meaningful models to develop a scientific understanding of how climate change will change fisheries.

The good news for now is that there are several approaches that can address the different challenges that may arise in a changing climate-ready fishery, and some of them have been tested and even used on the water. There are remarkable results obtained as a result of these researches, but they are far from being decided by the fisheries-related lawmakers and put into practice. It is very important to understand and take action on the requirements of the data obtained through science.

Will we be able to continue traditional fish farming activities?

According to FAO data, while world fish production was approximately 99 million tons in 1990, it increased to 122 million tons in 1997. When it comes to aquaculture production, the biggest increase in the sector is seen in aquaculture. While the volume of aquaculture was 13.1 million tons in 1990, it was 28.8 million tons in 1997. In the same period, the fishery products obtained from hunting increased from 68.9 million tons to 93.7 million tons. As of 1997, Turkey's total aquaculture production is around 500 thousand tons, of which 382 thousand tons are marine, 50.5 thousand tons are freshwater, 45.45 thousand tons are culture, 22.5 tons are other seafood.

When we focus on fish farming in the Aegean Sea, which is a little further north than the Mediterranean, the two most important species we encounter are Sea Bream (Sparus aurata) and Sea Bass (Dicentrarchus labrax). While these two species account for 95% of the total production, species such as Striped Bass - Granius - Meagre (Argyrosomus regius) and Yellowtail (Seriola dumerili) are also being tried.

Greece is the main producer of Sea Bass and Sea Bream within the European Union with an annual production exceeding 135.000 tons and therefore accounts for 60% of the European Union's supply and 24% of the global supply. In Greece, 65 companies have 328 farms and have €740 million investment capital. Other countries such as Spain and Italy account for a smaller but significant portion of its production for Europe, while Turkey is the largest non-EU producer, accounting for more than a third of global production. [link↗]

In Muğla, which is one of the special regions specialized in cages and especially in the field of aquaculture in the Mediterranean, the biology of the fish farmed on land is well adapted to the Mediterranean and Mediterranean climates. The main reason why these regions focus on aquaculture is the suitability of water temperature and the suitability of the climate.

Sea bream is a tolerant species when evaluated according to living conditions. Although the temperature range of the water he lives in is defined as 6 - 32 ºC, it has been determined that it shows the best development between 22 - 25 ºC. It has a low tolerance for extreme water temperature changes. Salinity tolerance was found to be 0.10 - 40%. They spawn in October-November when the water temperature drops to 14 - 19 ºC.

Seabass is a more tolerant species than sea bream. The living water temperature is defined as 5-28 °C, and it has been determined that it shows the best development between 20 - 23 °C. It lays eggs between 2 - 14 °C. leaving. Salinity tolerance was found to be 0.30 - 50%. While the oxygen solubility required by the Sea Bass is 7 - 8 mg / lt in order to continue breathing without being stressed, it is not desirable to drop it below 4.5 mg / lt.
 

Changes in the climate have important effects on fisheries, and they constantly affect each other. First, the oxygen holding capacity of water decreases with increasing water temperature. In other words, warm water can hold less oxygen than cold water, and hot water compared to warm water.

In addition to its oxygen holding capacity, warm water stratifies more easily in the column it is in. This stratification is thought to be one of the reasons why the sea loses oxygen. Since the stratified water has difficulty in moving within itself, oxygen cannot be distributed all over the underwater as it should be. [link↗] The second is that CO2 gas, the main source of which is air, passes into the water, and the pH of the water decreases, making it more acidic. Water with high acidity dissolves these calcareous structures of creatures such as crustaceans and corals, which tend to accumulate calcium-rich calter, making the water impossible for them to live in. The third is about the lack of immunity of fish. With the water being more acidic, while the fish are very small, they have a developmental disorder in the larval stage and have a hard time surviving. [link↗]

Besides, the temperature; It is also directly related to changes in physiological characteristics such as age at maturity, timing of reproduction, growth, survival and fertility.

Even these effects of climate on the sea alone endanger the future of the underwater world.

We must know that the sea will continue to change and it is not us, and if we do not adapt to it, the sustainable benefit we derive from fishing will only be a good memory of the past.

How will climate change affect the Mediterranean?

Whenever you look at climate change on a regional scale, it's not easy to draw a simple framework, says Piero Lionello, a climatologist and professor at the University of Salento in Italy, Mongabay. This means that the picture in the Mediterranean should scare us.

The Intergovernmental Panel on Climate Change (IPCC), in its report published in February 2022, announced that temperatures in the Mediterranean are increasing approximately 20% faster than the global average. Regional averages are currently 1.5 °C (2.7 °F) higher than pre-industrial levels. Globally, the increase was slower, reaching around 1.1 - 1.3 °C. Even if greenhouse gas emissions are cut completely today, the Mediterranean will probably be 2-4 °C warmer by 2100 than it was in the 19th century. The three warm continents, Europe, Asia and Africa, are clearly contributing to the warming of the Mediterranean because the land warms more easily than the sea. This is another indirect effect of climate.

Climate change and its harmful effects are forcing fish to relocate, and more and more species are migrating northward. It is not difficult to understand why, it is enough to empathize with yourself. Fish also desire to live in cooler places where they can breathe more easily. Farther North, cooler for now. The northward migration will harm the entire ecosystem.

The entry of species living under the main constraints such as temperature and salinity in the underwater geography they currently live in to the Mediterranean via the Suez Canal is a typical story of migration to the north. These immigrants, who reproduce uncontrollably and unlimitedly with the removal of the limiting factors on them, consume the underwater grasslands in the Mediterranean, Australia and Japan uncontrollably. As herbivores expand their habitats, they reduce kelp forests and leave barren deserts behind. The desert not only remains geographically in the form we see on land, but also represents the same thing underwater; a vast and frightening void that grows larger every day, freed from life. In Japan it is called isoyake.

Due to climate change, we are running out of time to continue fishing with the methods and information we have. Time flies so fast; we, our first or second generation, can also fish here under these conditions, but the few generations we're talking about are shorter than the blink of an eye in the world's own timeline. While crops grown in the Mediterranean and classified as economically main species have been extensively studied, there are significant gaps in the knowledge of how climate-related influences may affect fish culture in the future, which unfortunately hinders our capacity to assess and avoid ways to avoid potential hazards we may face.

We also have a lot of new components that are needed to put something new on top of it using the knowledge we have. What we need to realize and decide to move our business in that direction is that we will need new fishing approaches. A climate-reviewed and updated fisheries management will allow for the continued ability to sustainably source food from the sea and support businesses, protected areas and culture that interacts with the sea. The answer to the question I asked in the title of this chapter is yes, for a very short time; but not in the long run. New fishing methods, governance capabilities and even; we will need to find new species to breed.