Reconstructing 290 years of a data‐poor fishery through ethnographic and archival research: The East Pacific green turtle (Chelonia mydas) in Baja California, Mexico

Abstract

Evaluating historical changes in the exploitation of marine organisms is a key challenge in fisheries ecology and marine conservation. In the Eastern Pacific, marine turtles were exploited for millennia before systematic monitoring began <50 years ago. Using ethnographic and historical data, we generated a detailed reconstruction of the East Pacific green sea turtle (Chelonia mydas) fishery in Mexico's Baja California peninsula from 1700 to 1990. Sea turtles from the region's important feeding areas were a staple food source from the earliest phases of human occupation, dating back at least 12,000 years. In contrast with regions such as the Caribbean, small human populations and limited market access resulted in apparently sustainable turtle harvests until the second half of the 20th century. We found that the estimated annual catches between 1960 and 1980 exceeded the estimated annual catches of the previous 250 years by an order of magnitude, leading to the collapse of the fishery and the depletion of the green turtle population. A total ban on sea turtle captures in 1990, comprehensive nesting beach protection, and significant conservation efforts resulted in increases in breeding females on nesting beaches and catch rates in scientific monitoring on main feeding grounds since the early 2000s. This provides a positive outlook for this once‐depleted population segment. Although further research is needed to evaluate current conservation status, we have identified a date, between 1950 and 1960, which can serve as a reliable temporal reference for future evaluations of historical baseline abundance in this region.

Quantifying local ecological knowledge to model historical abundance of long-lived, heavily-exploited fauna

“…This research is part of an on-going collaborative process in the community of BLA which began in 2012 and has included ethnographic and historiographical research related to human–ocean interaction, along with a review of scientific literature ( Early-Capistrán et al, 2018 ). Background research helped define specific research questions, identify challenges in the study design and methods, and develop a general approach for integrating multiple forms of knowledge ( Crandall et al, 2018 ; Early-Capistrán et al, 2018 ).…”

“…Historiographical research situates biological questions in a socio-historical context, providing information on a species’ past abundance which can be correlated with time-frames, social processes, and management regimes ( Article S1 ) ( Crandall et al, 2018 ; Sáenz-Arroyo et al, 2005 ). Historiographical research helped us understand human-green turtle interactions in BLA over the past three centuries, identify the early 1960s as a period when human impacts precipitated a major decline in green turtle abundance in BLA, and establish the early 1950s as a time-frame for reconstructing baseline abundance before large-scale commercial exploitation ( Early-Capistrán et al, 2018 ).…”

“…Ethnography requires rapport, sensitivity to the cultural context, and developing an understanding of the social system on its own terms. Data are gathered broadly over topic areas and new questions are developed continuously ( Bernard, 2011 ; Early-Capistrán et al, 2018 ). Ethnography also helps identify biases by analyzing data within a social and historical context ( Drury, Homewood & Randall, 2011 ).…”

“…These efforts were fortified by the 1990 ban on all sea turtle use in Mexico, which established a legal framework to prevent harvests ( Diario Oficial de la Federación, 1990 ; SEMARNAT, 2010 ). However, abundance data and long-term trends prior to population collapse are needed to contextualize current population levels ( Early-Capistrán et al, 2018 ; Seminoff et al, 2008 ).…”

Diverse knowledge systems reveal social–ecological dynamics that inform species conservation status

“…In Mexico, declining trends from historical reconstruction of Gulf grouper fish abundance promoted conservation, whereas increasing trends from modern scientific data prompted consideration of increased catch quotas (Saenz-Arroyo et al, 2005). For East Pacific green turtle populations that collapsed from overfishing, reconstructing three centuries of fisheries data identified the timeframe most likely to represent appropriate conservation targets (Early-Capistran et al, 2018). Finally, knowledge of historically higher black abalone distribution and abundance assisted with restoration site selection (Braje, Rick, Erlandson, Rogers-Bennett, & Catton, 2016).…”