Biological parameters of the roudi escolar Promethichthys prometheus (Pisces: Gempylidae) off the Canary Islands

Evolving Fisheries: Today`s Bycatch is Tomorrow`s Target Catch - Escolar (Lepidocybium flavobrunneum) Catch in the U.S. Pelagic Longline Fishery~!2009-10-26~!2009-11-25~!2010-04-07~!

“…The overall mean size and length frequency distribution of escolar taken in the western North Atlantic Ocean (mean = 89.5 cm FL) was similar to that of the Pacific Ocean (90.0 cm FL) [29], but larger than those reported by Lorenzo and Pajuelo [31] in the eastern North Atlantic Ocean for round escolar. Because data in the eastern North Atlantic was collected from the hake hook-and-line fishery, it is probable that the difference in escolar length-frequency distribution re- sulted from either gear-size bias or was species size related.…”

“…Findings showed that weightfrequency distributions were uni-modal in all years, which was not evident in the present study for length-frequency. In general, the fishery in the western North Atlantic Ocean exploited a larger percentage of the length-frequency distribution range than the fishery did in the South Atlantic Ocean [4] or eastern North Atlantic Ocean [31], which might explain why catch rates have declined in the South Atlantic. The fork length to dressed weight association estimated for escolar in this present study was slightly lower than those calculated in the eastern North Atlantic (W = 4.7 x 10 -3 (L) 2.96 ; r 2 = 0.99; n = 308), but weights for this study were obtained from fish that were gutted and a different escolar species.…”

“…As such, they speculated that escolar might share similar trophic and reproductive behaviors as species in higher trophic positions. In the eastern North Atlantic Ocean, Lorenzo and Pajuelo [31] reported that male and female reproductive activity (GSI) for round escolar (Promethichthys prometheus) increased from March to July, and age 1 escolar otolith opaque formation occurred in July or August. Although seasonal variation might be associated with reproductive behavior, it is more probable that peak catches in the western North Atlantic Ocean are associated with feeding behavior.…”

“…Again, this might be due to some type of seasonal reproductive behavior, but the lack of reproductive data (Gonadossomatic Index [GSI]) makes it is difficult to speculate this difference. In the eastern North Atlantic Ocean (Canary Islands), Lorenzo and Pajuelo [31] reported that the reproductive period for roudi escolar extends from April to September, and peaks in June and July. However, the smaller size-at-catch in September in this present study may not be associated with any biological behavior, but just a product of the data set.…”

“…At this time, it is difficult to hypothesize how exploiting larger sizes of escolar in the western North Atlantic Ocean will impact the stock in the future, but this could be a future conservation and management issue. Assuming that age and growth for escolar in the western North Atlantic corresponds to that of the eastern North Atlantic round escolar [31], then exploited escolar catches in the western North Atlantic Ocean are already at maximum theoretical size-at-age (ages 9 and 10). Therefore, exploiting larger and older fish could significantly impact the stock if escolar catch rates and fishing effort was ever to increase in the western North Atlantic Ocean.…”