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Documentation of Sensitive and Commercially Valuable Species in Shrimp Trawler By-catch

Project Description

This study investigated what species are caught in by-catch with a focus on monitoring the extent of the extraction of sensitive and commercially important species. This was achieved by measuring the landed biomass and the size-frequency of the individuals encountered in by-catch.

Project Results

In the six years of the by-catch monitoring project, the presence of many endangered by-catch species has been observed. These species include the Pacific Seahorse (Hippocampus ingens), Totoaba (Totoaba macdonaldi), Loggerhead Turtle (Caretta caretta), Pacific Angel Shark (Squatina californica), Scalloped Hammerhead (Sphyrna lewini), Shovelnose Guitarfish (Rhinobatos productus), and Golden Cownose Ray (Rhinoptera steindachneri), all of which are listed on the IUCN Red List under varying degrees of severity from Critically Endangered to Near Threatened. Additionally there are several species common in the by-catch, which have commercial importance to the local panga fishers of Kino, whose populations in the Gulf of California have not been subject to scientific investigation. These include the Bullseye Pufferfish (Sphoeroides annulatus), and the Finescale Triggerfish (Balistes polylepis), and almost all of the 18 species of elasmobranchs. As the practice of selling by-catch to local panga fishers has become more prevalent, researchers have noted a marked increase in the retention of sensitive and commercially valuable species onboard trawlers. 

In a further study, data were collected from 18 trawls on one trawler over 4 nights in November of 2009 to address the presence of juveniles in the by-catch. Through literature reviews, it was determined that 100% of Finescale Triggerfish, 95% of Bullseye Pufferfish, and 80% of male and 78% of female Shovelnose Guitarfish recorded in our study were below the minimum known reproductive size, suggesting a significant impact from trawling on populations of juveniles of these species. 


 

Reports & Publications

  1. Meltzer, L., Blinick, N. and Fleishman, A. Management Implications of the Biodiversity and Socio-Economic Impacts of Shrimp Trawler By-Catch in Bahía de Kino, Sonora, México (in review)
  2. Research and Conservation Program Report (2007-2011). Prescott College Kino Bay Center for Cultural and Ecological Studies