Good Paper on General Effects of Climate Change on fish populations:
is attched.
----
Possible Historical Effects of Global warming:
- Change in average water temperature
- Changes in Surface currents
- Changes in deep water thermo-haline currents
- Formation of anoxic regions
- Intensified atmospheric pressure gradients => Increased storm frequency, increased upwelling?, increased advection?
- Increased C02 => increased pH
- (relatively) sudden climatic change events - due to change in currents
- Sea level rise => Change in vertical distribution
- Oceanic methane and hydrogen sulfide eruptions might increase
Geological record of mid-Cretaceous shows Carbon-rich (Black) Shales, indicating the prescence of extensive or global anoxic water masses. This corresponds with rapid global warming events and CO2 outgassing. Also around this time the source of deep water currents abrubptly shifted latitudes, which is believed to be at least partially responsible for the extinction of certain types of bivalves. Similar events are believed to have occurred at the Eocene-Oligocene boundary (a result of CH4 outgassing).
-New evidence for abrupt climate change in Cretaceous
Used modeling to look at triggers and feedback mechanisms. Once global warming has been initiated, it is likely to be worsened by positive feedback, such as by perturbation of marine hydrates. This means that in a warm world, even moderate changes in CO2 and CH4 concentrations can cause warming periods. This can also result in large regional climatic changes
Stronger wind fields might lead to enhanced upwelling in eastern boundary currents (Bakun 1990), which could increase nutrient availability at the surface.However, stronger thermal stratification and a deepening of the thermocline could prevent cool, nutrient-rich waters from being upwelled.
Harley, Christopher D. G. et. all. The impacts of climate change in coastal marine
Systems. Ecology Letters, (2006) 9: 228-241
----
Northern-Eastern Pacific Region:
http://www.pcouncil.org/groundfish/gfprimer.html
Important Species:
Groundfish (Rockfish, Flatfish, Roundfish, Sharks/Skates)
Salmon
Coastal Pelagic (Northern Anchovy, Pacific Sardine, Pacific Makerel)
Pacific Halibut
Migratory Species (Tunas, Sharks, Swordfish)
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 events, however, southern waters were in an EN- neutral state. There were also "strange weather" events occurring during this period. As a result, there was a drop in the biomass of plankton, which had a negative effect on resident fish and seabirds, as well as those that migrate to the NCC at certain times of the year.
-Peterson B
(4) The state of the California current, 2005-2006: Warm in the North, cool in the South
Paleoclimatic data suggest that upwelling in the California current system is positively correlated with temperature over millennial timescales (Pisias et al. 2001). 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. Modelling work suggests that increased offshore advection is often negatively correlated with adult population size, and very strong upwelling could theoretically prevent a species from maintaining an adult benthic population at particular sites.
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.
----
Southern-Eastern Pacific Region:
Coastal Fishery off of South America resides at an upwelling zone. This upwelling goes through cycles during ENSO (El Nino - Southern Oscillation) cycles. Somatic growth rates were low for those recruited during EN (El Nino - warm years) and high for those recruited during LN (La Nina - cool years) events, compared with transitionary years. Mortality rates were highest during EN events and lower during LN and transitional years. The paper suggests that productivity (as a bottom-up driver) is directly linked to the natural mortality rate of the fish in this region. During ENSO the average water temperature will increase 4-5 degrees during EN and decrease 2-3 during LN. Productivity drops durrin EN and increases during LN.
-(1) Eduardo Herna´ ndez-Miranda - F. Patricio Ojeda
Inter-annual variability in somatic growth rates and mortality of coastal fishes off central Chile: an ENSO driven process?
Given projected rates of the accumulation of atmospheric CO2, 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. This paper, however, maintains that it is more likely that the climate will follow a ENSO pattern similar to that of current years.
-(2) Collins Matthew
El Nin˜ o- or La Nin˜ a-like climate change?
Another evaluation predicts global warming will ultimately lead to longer and weaker ENSO cycles. This occurs via complex interactions between currents and atmospheric circulation.
-3) Qiong Zhang - Haijun Yang - Yafang Zhong -Dongxiao Wang
An idealized study of the impact of extratropical climate change on El Nin˜ o-Southern Oscillation
It is likely that El nino events will increase with either frequency or intensity, even if the climate stays relatively normal in other years.
Harley, Christopher D. G. et. all. The impacts of climate change in coastal marine
Systems. Ecology Letters, (2006) 9: 228-241
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 additiional hits during el-nino years, so aditional 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.