Effect of Climate fluctuations on Fisheries in a Sub-Arctic Environment

by Neha Vaingankar

Climate change influences marine ecosystems in different ways. For example, fishery management plans fail because of unanticipated changes. Intense exploitation of fisheries may lead to bottom-up control of the food chain and greater sensitivity to climate change. Because climate change occurs so slowly, it is difficult for scientists to see the ecosystem impacts right away, but gradually, the effects become evident in the interactions between fishing and environmental variability. In this paper Durant et al. (2013) aim to explore the effects of fishing and climate change on the structure of populations of sub-Arctic ecosystems, especially when it comes to temperature fluctuations and fishing-induced changes in spatial and demographic population structure. They are particularly interested in shifts in spatial and demographic population structure that affect the recruitment and population growth rate. The results show some patterns as well as differences in the relative importance of fishing and climate on the populations and ecosystems examined. Continue reading

Do Marine Protected Areas Save Seychelles Sea Cucumbers?

by Neha Vaingankar

Marine protected areas are a major cause of dispute especially in coastal and island regions like Seychelles, off the western coast of Africa. In recent times, tropical regions all over the world have experienced a huge boom in fishing of holothurians (sea cucumbers). Almost all of the holothurian fisheries are considered fully exploited, in decline, or entirely collapsed. The reason for the high demand is for the holothurian’s medicinal purposes as well as its supposed aphrodisiac qualities. In many tropical coral reef regions, locals rely on these invertebrates for their livelihoods. However, due to the density-dependent reproduction patterns and late maturing of these organisms, holothurians are very vulnerable to over-exploitation. Many MPAs were established in Seychelles 20 years ago that pre-date the wave of heavy exploitation in current times. Cariglia et al. (2013) aims to understand the effectiveness of these MPAs and measure the economic value of these holothurians. Continue reading

Lagged Social- Ecological Responses to Climate and Range Shifts in Fisheries

Many studies have been done to test the effects of marine species migration patterns and habitat changes due to climate change and have shown that many middle latitude species have moved north towards the poles to escape the rising temperatures. Pinsky and Fogarty (2012) investigating the effects of climate change on marine fisheries in the northeastern United States, also demonstrate a northward shift of these species, along with their target (or indicator) species. However, interestingly, the marine fisheries in question did not move as far north, indicating some sort of an economic and regulatory constraints. Pinsky and Fogarty examined species in the northeastern United States. They hypothesized the northern states would receive a higher proportion of total landings as the species moved north and the southern would receive lower. Landings are the total tons of catch. Pinsky and Fogarty also find that economic and regulatory considerations have s significant impact on fishery species.—Neha Vaingankar

M. Pinsky, M Fogarty, 2012. Lagged social-ecological responses to climate change and range shifts in fisheries, Climate Change, Vol 115, 883-891

                  Pinsky and Fogarty at Princeton University examine four species of marine animals: lobster, yellowtail flounder, summer flounder, and red hake. The mean latitude was calculated as a biomass-weighted average latitude at which the species appeared in the research survey shows. Then species distribution was characterized annually by their mean latitudes. The commercial landings (weight of catch) and value of catch were used in the calculations of the mean latitude as the average latitude of the sates in which the species were caught, weighed by biomass landed. Also, they examined the preferred temperatures of species landings in each state. Much of the data were taken from other studies and sites like the National Marine Fisheries Service.
                  The data show that the both fisheries and their target species shift together. The indicator/target species is extremely important in any ecosystem. It represents the balance and overall health of a habitat.  However, in some areas, there was a much weaker correlating between the two like in the case of the lobster and yellow tail flounder. The two species went much farther north than their target species. Landings shifted towards the north only slightly as the species shifted north.  In the case of the red hake, there was less of a northward shift. The changes in latitude were not very high, but they all did exist.
                  Overall, there was a significant shift of fisheries northward. However, because of this change in population density, fishers have few options. Either they change their primary port for landing fish, or travel further away from their current spot. Despite she shifts northward as the data suggest, Fishers in the south are still attempting to make a living. They look even harder for fish with depletes the population further for northern fishers. As there becomes a greater shift in fisheries, boats will begin to move along with them. This will eventually lead to higher travel costs and finally higher process for fish. Pinsky and Fogarty believe that fishing will soon become a problem, one that will eventually lead to social and economic strife. However, in order to sustain our fisheries, efforts to save the fisheries include setting up bans and constraints on the way that fisheries respond. This will ensure that our fisheries will be able to sustain costal economies, even if the temperature is still warm.

Effect of Climate Change on Global Fisheries Catch

Climate change is huge cause for concern to many different ecosystems, including marine fisheries. Cheung et al. (2013) delves into the effects of rising sea surface temperature (SST) on the mean temperature of the catch (MTC). MTC is an index that represents the average inferred temperature preference of a species weighed by the annual catch. Overall, the results showed that the composition of marine fisheries catch is significantly related to changes in SST. More warmer water species are being caught at higher latitudes and fewer subtropical species are being caught in the tropics. This is cause for concern as many developing costal nations rely on the maritime industry, not only environmentally, but economically and socially as well.—Neha Vaingankar
W. W. L. Cheung, R. Watson, D. Pauly, 2013, Signature of ocean warming in global fisheries catch, Nature 497, 365—368.

W.W. Cheung and his colleagues at the University of British Columbia found that the global MTC increased each decade from 1970 untill 2006, specifically in non-tropical the northeast Pacific Ocean and northeast Atlantic Ocean. Over these years, global temperature preference increased at a rate of about 0.2 °C every decade, and the effects were even more pronounced in non-tropical areas. To quantify this, Cheung et al. created large marine ecosystems (LME’s) to account for most of the world’s fisheries. Overall, 52 were used. Spacing of fisheries depends on the best possible environment for those species to live in, including biotic and abiotic factors. Distribution of some marine fisheries has changed over time due to changes in these ocean conditions. In measuring the MTC, Cheung et al. inferred the temperature preference of each species on the basis of its modeled distribution from the “Sea Around Us Project” and the Food and Agriculture Organization’s fishery database.
Cheung et al. assessed the preference of fish species in different areas by calculating the MTC. Global warming leads to catching more warm water species overall and therefore a higher MTC. Cheung et al. found that continents towards the north of the globe, like Europe, North America, and northern Asia all show a higher rate of change in SST with MTC rising at higher latitudes, meaning warm water species are being caught further north. Cheung et al.also found that MTC changes and SST changes correlate in almost every LME implying that catching warmer water species is a result of changes in ocean temperatures. Tropical marine ecosystems also correlated to the MTC, which stabilized at twenty-six degrees Celsius. 
Because MTC is the main index used in figuring out the effects of climate change on marine fisheries, Cheung et al. explains why MTC works. Firstly, in the North Sea, scientists compared the change in MTC from the catch data to that of data collected from deep-sea trawlers that scrape the bottom of the ocean for fish and other marine organisms. This shows that the MTC is consistent regardless of what depths the species are coming from. Another example of why MTC is a valid proxy to examine changes in composition of catches in a region in relation to the temperature preference of the exploited animals is because an increase in fishing conservation efforts is related to the temperature preference of the exploited species. However, the positive correlation between the two was only found in about 19 LMEs, which shows that the MTC trend is not a result of the depletion of large fish by fishing. Next, in the case of misreporting of catch data, initial MTC values were not significant. However, after fixing the catch values, the MTC rates of change became significant. This sort of change in significance was not seen when different SSTs were used to calculate species’ temperature preference.

Overall, the results show that the change in composition of marine fisheries catch is significantly correlated with the temperature increases in the ocean. These changes in temperature will have a large effect on the socio-economic situation of poorer countries in the tropics, which rely on these fisheries for their income.