David A. Demer

Optimizing Fishing Quotas to Meet Target Fishing Fractions of an Internationally Exploited Stock of Pacific Sardine

AbstractTwo stocks of Pacific Sardine Sardinops sagax migrate seasonally and synchronously along the west coasts of Mexico, the USA, and Canada. Landings from the two stocks are currently combined in U.S. assessments of the northern stock, but the stocks may be differentiated by their associated seawater habitats, which are predominantly characterized by different ranges of sea surface temperature. We compared the combined and temperature-differentiated landings of the two stocks in each country for the period 1993–2011, demonstrating how different attributions of the landings affected the estimated annual fishing fraction (F) for the northern stock. Using combined or stock-differentiated landings and assessed biomasses, we found that the current harvest control rule (HCR) for Pacific Sardine has not consistently maintained a total F below the U.S. target value because the “distribution” parameter (used to account for the northern stocks proportion in the U.S. Exclusive Economic Zone [EEZ]), has not adeq...

Target strength of skipjack tuna (Katsuwanus pelamis) associated with fish aggregating devices (FADs)

We thank the following organizations and people for their support of this work: the governments of Kiribati, Tuvalu, and Tokelau which permitted this research in their EEZs; Albacora for allowing this work aboard F/V ALBATUN TRES; Fishing Master Euken Mujika; the captain and crew; the scientists and divers J. Filmalter and F. Forget are thanked for invaluable insight about fish behaviour, vertical stratification and non-target species composition at FADs; Hector Pena for providing instruction on the sonar setup and analysis; Yolanda Lacalle for the illustration in Figure 2; and Andres Uriarte for advice concerning transmission of statistical errors. The research reported in the present document was funded by the International Seafood Sustainability Foundation (ISSF) and conducted independently by the authors. The report and its results, professional opinions and conclusions are solely the work of the authors. This paper is contribution 843 from AZTI (Marine or Food Research).

A Method to Consistently Approach the Target Total Fishing Fraction of Pacific Sardine and Other Internationally Exploited Fish Stocks

AbstractThe “northern” stock of Pacific Sardine Sardinops sagax is fished by Mexico, the USA, and Canada. Without an international management agreement, the U.S. Pacific Fishery Management Council prorates its target total fishing fraction (F) in its harvest control rule (HCR) by 0.87. This is the proportion of the stock that it deemed in 1998 to be present, on average, during summer–fall 1964–1992 in the U.S. Exclusive Economic Zone. However, the portion of the stock in U.S. waters is variable, depending on the environment and stock biomass and demographics. Furthermore, irrespective of the stock distribution, the combined foreign and U.S. landings may exceed those determined by an F of 0.15, potentially reducing the stock biomass and yield. This occurred each year during 2001–2014, and the F (mean = 0.22; SD = 0.06) trended upward. To more consistently approximate the target F, a method was proposed to set harvest quotas with accounting for predicted foreign landings. We refined the method by adding a p...