Mean Temperature of Catch Shows Impact of Ocean Warming on Fisheries

by Hannah Tannenbaum

Understanding the impact of climate change on marine fisheries viability has important implications for the sustainability of the industry. Cheung, Watson and Pauly (2013) collected catch and supplemental data, and computed mean temperature of catch, MTC from average inferred temperature of over 900 species of exploited fish weighted with their annual catch rates. MTC was inferred from modeled distributions for the years 1970 to 2006. It was shown that there is a positive relationship between increased rate of SST change and increases to MTC, and that global fisheries have responded with ‘tropicalization,’ shifts. Continue reading

Under-reported Overfishing by Chinese Threatens World Fisheries Estimates

by Hannah Tannenbaum

Fisheries catch data are the only real means for the fisheries industry, economists, and environmentalists to ascertain the population status of fished stocks. Therefore, accurate reporting of catch data is of the utmost importance. It was discovered in 2001 that China was drastically over reporting their domestic catch in order to achieve the appearance of uninterrupted expansion and success. China has an immense fishing fleet, but is also outside of agreements regarding EEZ and FAO of the UN, and therefore their catch records are important for global estimates, but particularly unreliable as currently reported. While estimates have been made to correct for decades of over-reporting in Chinese domestic fisheries, they are also major participants in distant-water fisheries. Pauly et al. (2013) used statistical extrapolations to estimate the Chinese distant-water catches and found severe under-reporting compared to the figures reported to FAO. While the interpolations have high levels of uncertainty, they nonetheless suggest immense inaccuracy of global fisheries catch statistics which has wide implications for employment, economics and ecology. Continue reading

From Primary Predator to Picked-on Prey: Shark Fishery in the Pacific Ocean

by Hannah Tannenbaum

In 2001 sharks were first listed as endangered species, and since then several measures have been enacted towards their protection. However, the majority of shark fishing is an incidental byproduct of purse seine and long-line fisheries which operate outside of national Exclusive Economic Zones (EEZ). Therefore the effectiveness of international treaties banning shark finning is hard to discern. Another major difficulty in assessing the effectiveness of conservation is the paucity of data on shark population size and structure. Clarke et al. (2013) collected and analyzed onboard observer data on shark catches from 1995–2010 in order to evaluate the threat to sharks from commercial fishing, and determine changes in shark populations after finning bans were established. The authors analyzed data on blue, oceanic whitetip, silky, and mako sharks because of their tendency to appear as bycatch in the Pacific tuna fishing industry. Through the analysis of observer data, no clear trend of reduced catches was found consistently for any species, any area, for either type of fishery. The authors suggest that shark retention bans may have a greater impact on population size than finning bans, and that management and monitoring must be made more consistent in order to properly evaluate conservation. Continue reading

Calculating Overfishing for Tuna and Billfish


by Hannah Tannenbaum

Threatened fish stocks have generally only been identified as being overfished and potentially reaching extinction once they have already been exploited and are in population decline. This makes remediation efforts for overfished stocks much more difficult, because much of the damage has already been done. Burgess et al .(2013) defined the “eventual threat index” (T), taking into consideration primary effects on overfishing potential. The variables they used to understand exploitation potential include: vulnerability, population size, average catch-per-unit effort, maximum per-capita growth rate, as well as profitability. In particular, this study examined multispecies fisheries, referring to fisheries in which there is a target species, but often the fishery affects many other species as well. Therefore they identified the “key” species as the most commercially valued, or most environmentally sensitive, and therefore the most likely to be exploited. The authors then applied the eventual threat index for historical information on four Pacific tuna and billfish populations, and were successfully able to Continue reading

Selective Pressures Impact on Fisheries Management Reference Points

Fisheries management is a diverse field, essentially reliant on ecological reference points as proxies for fisheries stability and sustainability. Reference points are generally based on population dynamics such as maximum sustainable yield (MSY), spawning stock biomass (SSB), fishing mortality (F), and yield-per-recruit relationships among others. Heino et al (2013) defined fisheries-induced evolution (FIE) as a selective mechanism ,which can impact the stock population characteristics and life history traits through the shifting of reference points. Although it has been theorized that fisheries-induced evolution is taking place in various fish stocks, predominantly seen through reduced fish sizes, quantitative evidence for FIE actually occurring in the wild is still unavailable. Nonetheless, the authors conclude that reference points are shifting due to FIE, climate change, or other environmental and ecological factors, and emphasize that reference points must be re-evaluated and adjusted to be current and effective for fisheries management and conservation. – Hannah Tannenbaum

Heino, M. et al. 2013. Can Fisheries-induced Evolution shift Reference Points for Fisheries Management? ICES Journal of Marine Science 70, 707 – 721.

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Do Fish Sweat? North Atlantic Fisheries Response to 2012 Temperature Anomaly.

Sea surface temperature (SST) is a key signaling factor for marine species for a variety of life-cycle events: growth cycles, breeding times, migration times, range location, among others. Fisheries management in the U.S. is cognizant of the importance of temperature, as it has been used as the main parameter for the establishment of species-specific fishing seasons to optimize legal size limit catches annually, as well as the location of set fishing grounds based on seasonal migrations. The authors specifically examined the changes in fisheries after the 2012 Northwestern Atlantic temperature anomaly, in the hopes of extrapolating how fisheries management will be disrupted by changing climate. Mills et al (2013)found that the 2012 temperature anomaly for sea surface was 2°C warmer than the average sea surface temperatures for 19822011.-Hannah Tannenbaum
Mills, K. et al. 2013. Fisheries management in a changing climate: lessons from the 2012 ocean heat wave in the Northwest Atlantic. Oceanography 26, 1–6.

                  Climate change became tangible for many Americans in 2012 with record high temperatures and the experience of Hurricane Sandy on the eastern seaboard. Temperature changes are important for marine fisheries; temperature norms have allowed for the establishment of fishing seasons for specific seasons, and set fishing grounds seasonally. Mills et al. examined the ecological responses to the 2012 temperature anomaly in the North Atlantic. By examining how various fisheries were disrupted spatially and temporally, the authors extrapolated future effects of continued oceanic warming. Ultimately, the authors recommend that fisheries management and regulations, specifically fishing seasons and fishing grounds, must be adapted to climatic changes in order to both preserve the fishing industry and prevent overfishing.
                  The authors examined the effects of the 2012 abnormal sea surface temperature through the example of the Atlantic lobster fishery. Lobsters migrate inshore annually based predominantly on temperature patterns. Their season for fishing is set for the summer based on the temperatures suitable for moving inshore. The authors found that in 2012 the temperature anomaly affected lobster migration such that there were record catches in June and July, but the season usually peaks in late August. While the higher catch success rate may be advantageous in the short term, warmer temperatures could reduce lobster fitness by cutting short the growing period. Additionally it was noted that the 2012 spike in lobster availability was not actually beneficial but instead led to price crashes for the price of lobster, adding instability to the fishery.

                  Other fisheries besides the lobster fishery were disrupted or adversely affected by the 2012 sea surface temperature anomaly in a variety of different ways. The disjointed responses to ocean warming will pose a particular challenge for proper maintenance of fishery regulations in the future. The authors suggest that these management institutions must adapt to be more holistic and flexible with their regulatory measures, to take into consideration climatic changes for past regulatory ordinances, and looking towards the future.  

Fishery employment and fishing for employment.

Marine fisheries are a huge international industry, with a multitude of implications for different sectors: environment, health, employment, trade, industry, cultural heritage, and subsistence. However, accuracy in reporting in fisheries remains a problem, largely due to the lack of consensus of actual worldwide fisheries employment. Teh and Sumaila (2013) quantified worldwide fisheries employment, including direct and indirect employment, and recognition of small-scale fisheries. Using employment and demographic data from 144 nations, as well as the Monte Carlo algorithm to fill in missing data, the authors estimated that some 260 million people are involved in the fishing industry, of which about 22 million are involved in small-scale fisheries. – Hannah Tannenbaum
Teh, L., Sumaila, U R. 2013. Contribution of marine fisheries to worldwide employment. Fish and Fisheries 14, 77-88.

                  The accurate evaluation of marine fisheries contribution to worldwide employment may further our understanding of fisheries in terms of socio-economics and environment. Different nations across the world are involved in fisheries but vary in terms of scale and primary purpose. The authors first found that developed countries were typically fishing on a much larger scale than developing countries; this has implications regarding direct and indirect fisheries employment as well as underreporting from “small-scale,” artisanal, or subsistence fisheries.
                  To compensate for the paucity of data regarding small-scale fisheries, the authors first defined small-scale, then classified countries by the UN Human Development Index status and by geographical location, and then used a probability algorithm to estimate the small-scale fishing component. Small-scale fisheries operations were classified as “being individuals living in rural areas in the coastal zone,” (Teh 2013). The Monte Carlo algorithm was applied to estimate the number of small-scale fisheries, which uses repeated random sampling with known variables, such as the rural coastal population, to fill in unknown variables, individuals involved in fisheries. The authors recognize that uncertainty remains as to the exact number of small-scale fisheries world-wide, but found that deviations on estimations of small-scale fisheries were most closely matched to coastal population trends, which could provide insight for future work.
                  Ultimately, through national databases and probabilistic estimations, the authors estimated that 260 million people are either full-time or part-time employed directly or indirectly in marine fisheries. They also approximated that 22 million people were involved in small-scale fishers, and that 78% of global fishers workers are from the developing world.
                  Since global fisheries contribute to national economies, cultural identities, and environmental security, knowledge of the scale and magnitude of the international fisheries industry is crucial to its preservation. The authors were able to use national statistics and probabilities to estimate the world wide employment of fisheries, and elucidated where further research and reporting is needed.