13 Team 3: Climate Change

    Over the past century or so, the earth has seen a significant rise in average global temperatures. Whether this is primarily a result of anthropogenic influences, or of natural repeating fluctuations in climate, global warming will have a profound effect upon the oceans and should therefore be of great concern to anyone in charge of global fisheries. It is also very likely that global warming will accelerate in the near future due to positive feedback mechanisms. Climate change is somewhat difficult to monitor, and even more so to predict accurately. Despite this, research on current systems as well as research into past global warming events provides us with an idea of what might be expected in future years. By knowing the general trends of climate change, an understanding effect on fisheries can be extrapolated.

    The melting of glacial ice and the thermal expansion of ocean water will cause sea levels to rise. While this is unlikely to have a great effect on most ocean life, there are some cases where the change might be too fast for certain ecosystems to adapt. This could be a particular problem with coral reefs, which might not be able to grow fast enough to counteract the rise in sea level.

   The change in temperature will cause changes in water chemistry, which in turn may have drastic effects on certain species, especially those with low tolerances. Many life processes in animals and plants are dependent on temperature, and could be significantly altered by a rise of even a few degrees in temperature. Higher temperature waters, such as those in the tropics have less primary production in the form of phytoplankton, which almost all fish derive their energy from. Addition of fresh water from melting ice caps decreases the salinity of ocean regions, which can be detritimental to species with low tolerances to changes in salinity.

    As seawater warms, it also loses its ability to dissolve certain gases. One of these is O₂, which is essential to all animals for respiration. Geological records of past global warming events show evidence of severe periods of anoxia on large to global scales. A significant drop in the levels of O₂ would result in result in a decrease of metabolism of animal life. CO₂, however, is not near its saturation levels in the ocean. As CO₂ levels rise, it will be taken in by the ocean where it reacts to form Carbonic acid, thus lowering the pH of the water. Acidic conditions could have detrimental effects on sea life, especially those that depend on significant amount of CaC0₃, such as shellfish.

    The introduction of fresh water from melting ice caps can also affect deep-water thermo-haline currents. Because it lowers the density of water in polar region, it can prevent the sinking of water here, thus weakening or stopping the overturn of the ocean. Historically this has resulted in severe cases that cause a build up of toxins in the ocean, which is linked to mass-extinction events. It is also possible that a similar event could prevent the transport of water from the tropics to the poles, causing a period of rapid climate change.

    The warming of the atmosphere is expected to result in intensified atmospheric pressure gradients. There is already some evidence that this has resulted in increasing storm frequency and intensity in recent years. Atmospheric conditions are largely responsible for surface currents, which transport water in the surface layers of the ocean where most of the biomass resides. Modeling predicts that advection and upwelling will increase as a result of global warming, especially in the eastern boundary currents. Increased advection is generally linked to decreased biomass. Upwelling can often increase the biomass as it provides a source of cold, nutrient-rich water to the surface, but a strong upwelling current can also be disruptive. It is also suggested that global warming could increase thermal stratification, which would decrease upwelling.

    Although predictions can be made about what will happen, no one is sure exactly how global warming will effect the oceans and fish populations. However, the climate is an important factor in the formulation of a plan for fishery management. The climate will not change uniformly over the entire globe. For instance, climate the effects of global warming are likely to be more pronounced in the polar latitudes. Thus our predictions must be formulated specifically for different regions. Due to the importance of climate change to fisheries, we propose that we should set up a system for analyzing data as global warming progresses. Information such as temperature, salinity, pH, gas solubility, biomass, species population, and current strength and direction in order to look for trends that would allow us to better predict the future climate of various regions. Also, more work has to be done, determining quantitatively how fish populations react to climate change. As these quantities are monitored, we should begin to see trends in the progression of climate change.
    Once trends have been determined the plan for fishery conservation would then be modified in order to counteract whatever effects were being caused by the climate change. For instance, with many of the predicted changes, the ecosystem could be able to support a smaller population of fish than it does currently. As soon as this realization comes about, restrictions must be changes to fit the reality of the situation. For this reason we propose using quotas as our main form of restriction. This would allow for the most accurate control over the number of fish we are taking out of the environment, and allow the restrictions to be changed more easily when a new trend in climate change is found. The most important aspect of the plan with respect to climate change is that it has to modifiable, so that we can be constantly improving our approach as we improve our understanding of climate changes effects. If we are to this approach is most likely valid for other aspects of this problem as well. This approach, however, would require a great improvement in our understanding of fish population dynamics. Therefore, it would be prudent to apply other restrictions until this point is reaches.

   We do have some predictions for possible future effects of climate change on certain areas:

• From 2003-2005, the west coast (NCC, Northern California Current) of the United States went through a warming period similar to those related to ENSO (El Nino - Southern Oscillation) events, however, southern waters were in an EN- neutral state. Paleoclimatic data suggest that upwelling in the California current system is positively correlated with temperature over millennial timescales. Furthermore, upwelling along the California coast has increased over the past 30 years, and these increases are expected to continue. It is also fairly certain that advection should increase in the California current. The upwelling could have a beneficial effect on the ecosystem if it is not too strong, but advection would likely have an adverse effect.  Therefore, it is most likely that the populations of fish in this region will be negatively affected by climate change. This would have to be taken into account and stricter enforcements would be needed to produce the same results that would be expected without climate change. However, if the benefits of the upwelling are seen to be outweighing the harm done, these restrictions could probably be relaxed.

• Coastal Fishery off of South America resides at an upwelling zone. This upwelling goes through cycles during ENSO cycles. Mortality rates were highest during EN events. There is a chance that there could be a long toward shift in the climate towards the EN, which would most likely have a negative effect on fish populations. Another evaluation predicts global warming will ultimately lead to longer and weaker ENSO cycles. This occurs via complex interactions between currents and atmospheric circulation. If the first case occurs and the system shifts in the El Nino spectrum, then the fish populations in this region stand to be much lower than would be expected otherwise. This would have to be taken into account and stricter enforcements would be needed to produce the same results that would be expected without climate change. The fisheries in these regions might also take additional hits during el-nine years, so additional protection might be required for these years. If the second case happens, then climate will probably play a much smaller role, and plans can be carried out without too much modification for climate change.

• The deep seas and international waters outside of EEZs (Exclusive Economic Zones) are being increasingly fished; species such as the orange roughy, tuna, and shark are three major targets in these areas. Many such organisms are especially vulnerable to overfishing due to their long reproductive cycles; orange roughy, for example, have been found to live up to 240 years. Much of deep sea life is localized to specific areas called "hot spots," centered around particular conditions including temperature, salinity, and seamounts (mountains submerged in the ocean). This makes deep sea creatures particularly vulnerable to climate change. Also, plankton is the basic food source for many of these creatures, including fish larvae. Plankton must follow ocean currents, and is dependent on certain atmospheric conditions.  It has already been found that increasing ocean temperatures decrease plankton levels through ENSO cycle studies. Combined with the changes in current and composition mentioned earlier, deep water fishing will certainly be threatened by climate change. The uncertainly lies in the timescale and magnitude of climate change, and we need to closely monitor this in order to change specific and general strategies for maintaining deep water fish stocks.

• We support efforts to mitigate human impact on climate change, but recognize that it is outside the scope of the project.