Arreguin-Sanchez F.,Centro Interdisciplinario Of Ciencias Marinas Cicimar |
Salas-Marquez S.,National Polytechnic Institute of Mexico |
Garza J.C.,National Oceanic and Atmospheric Administration |
Roman-Rodriguez M.J.,Comision de Ecologia y Desarrollo Sustentable del Estado de Sonora
Endangered Species Research | Year: 2016
The lack of long-term monitoring programs makes it difficult to assess signs of population recovery in collapsed marine populations. Fishery-induced changes in the life history of exploited marine fishes, such as truncated size and age structure, local extirpations, reductions in age at maturity, and changes in mortality patterns, have occurred. In the present study, we explored life history aspects of totoaba Totoaba macdonaldi, almost 40 yr after a population collapse, to examine whether totoaba maintained their life history pattern and to identify the potential threats of using fishing gear (hooks, gillnets). The results of the present study indicate that the totoaba size structure was not truncated as expected in overexploited populations; indeed, it was similar to that observed in the past. Totoaba have maintained their known historical distribution range. The spatial size structure and temporal distribution followed the known migration patterns of totoaba. Total and natural mortality were similar. Contrary to recommendations for sustainable fisheries, caught fish contained a large number of juveniles, irrespective of method used. We conclude that the general life history (size structure, distribution, migration, and mortality) has not changed since the fishery collapse. However, the choice of fishing gear could compromise a positive recovery trend of the population. Moreover, poaching is a major ongoing threat to the recovery of totoaba. © The authors 2015.
Edwards T.,University of Arizona |
Vaughn M.,Sundance |
Rosen P.C.,University of Arizona |
Melendez Torres C.,Comision de Ecologia y Desarrollo Sustentable del Estado de Sonora |
And 4 more authors.
Journal of Biogeography | Year: 2016
Aim: We examine the role biogeographical features played in the evolution of Morafka's desert tortoise (Gopherus morafkai) and test the hypothesis that G. morafkai maintains genetically distinct lineages associated with different Sonoran Desert biomes. Increased knowledge of the past and present distribution of the Sonoran Desert region's biota provides insight into the forces that drive and maintain its biodiversity. Location: Sonoran Desert biogeographical region; Sonora and Sinaloa, Mexico and Arizona, USA. Methods: We examined wild tortoises from Mexico (n = 155) and Arizona (n = 78), spanning their known distribution. We used mtDNA sequences to reconstruct matrilineal relationships and 25 microsatellite (STR) loci for Bayesian analyses of gene flow. We performed clinal analyses on both mtDNA and STR loci to determine the position and amount of introgression where lineages co-occur. We used GIS to assess the association of genetic structuring with ecological features. We used these data in a hypothesis-driven approach to assess different models of how genetic diversity is maintained and distributed in G. morafkai. Results: Gopherus morafkai was found to comprise genetically and geographically distinct 'Sonoran' and 'Sinaloan' lineages. Both lineages occurred in a relatively narrow zone of overlap in Sinaloan thornscrub, where it transitions into Sonoran desertscrub. Limited introgression occurred at the contact zone. The best-fit model suggests that these lineages diverged in parapatry where the distribution of genotypes is environment-dependent and introgression is inhibited by exogenous selection. Main conclusions: The historically shifting ecotone between tropical deciduous forest and Sonoran desertscrub appears to be a boundary that fostered divergence between parapatric lineages of tortoises. The sharp genetic cline between the two lineages suggests that periods of isolation in temporary refugia due to Pleistocene climatic cycling influenced divergence. Despite incomplete reproductive isolation, the Sonoran and Sinaloan lineages of G. morafkai are on separate evolutionary trajectories. © 2016 John Wiley & Sons Ltd.
Erisman B.E.,University of California at San Diego |
Apel A.M.,Environmental Defense Fund |
MacCall A.D.,Southwest Fisheries Science Center |
Roman M.J.,Comision de Ecologia y Desarrollo Sustentable del Estado de Sonora |
Fujita R.,Environmental Defense Fund
Fisheries Research | Year: 2014
We applied several data-poor techniques to perform an assessment of the Gulf corvina (Cynoscion othonopterus) fishery in the Gulf of California from 1997 to 2012 and to investigate the effects of gear selectivity and age-dependent variation in spawning frequency on estimates of sustainability in spawning aggregation fisheries. The length composition of the catch varied significantly among years but showed no clear directional pattern. However, the average length was above the long term average after the implementation of a regulation that standardized mesh size of nets, and the average length of fish captured after the implementation was significantly higher than during previous periods. Results using three simple metrics based on catch length compositions indicated that fishing activities were sustainable due to the exclusion of juveniles from the fishery and the targeted harvest of adults at the optimal length. However, the low proportion of older, fecund fish in the fishery is a serious cause for concern. Modeled estimates of spawning potential ratios (SPR) were consistently higher when spawning frequency was assumed to be age invariant and were significantly higher after the implementation of gear regulations. However, SPR values only reached levels above 35%, a common reference point for sciaenid fishes, during the current fishing period (2010-2012) under conditions of age invariant spawning frequency. Results of this study support previous claims that suggest estimates of reproductive potential are highly sensitive to age-dependent variation in spawning frequency and imply that such details related to spawning behavior require more attention, particularly for fisheries that target spawning aggregations. Our results also suggest that spawning aggregations can be harvested sustainably through conventional regulations if juveniles are excluded, fish are harvested at optimal length, and older, fecund individuals are protected from harvest. Given the uncertainty of the status of the corvina fishery based on the discordant results of this study and the inherent vulnerability of the species to overfishing, We recommend the precautionary approach be applied to management decisions until more robust information is acquired on stock abundance, the relationship between spawning frequency and age or length, and reproductive output. © 2014 Elsevier B.V.
Berry K.H.,U.S. Geological Survey |
Brown M.B.,University of Florida |
Vaughn M.,179 Niblick Road |
Gowan T.A.,U.S. Geological Survey |
And 3 more authors.
Journal of Wildlife Diseases | Year: 2015
We conducted health evaluations of 69 wild and 22 captive Morafka’s desert tortoises (Gopherus morafkai) in Mexico between 2005 and 2008. The wild tortoises were from 11 sites in the states of Sonora and Sinaloa, and the captive tortoises were from the state-managed Centro Ecológico de Sonora Zoo in Hermosillo and a private residence in the town of Alamos. We tested 88 tortoises for mycoplasmal upper respiratory tract disease (URTD) using enzyme-linked immunosorbent assays for specific antibody and by culture and PCR for detection of Mycoplasma agassizii and Mycoplasma testudineum. Fifteen of 22 captive tortoises had one or more positive diagnostic test results for M. agassizii whereas no wild tortoises had positive tests. Tortoises with positive tests also had significantly more moderate and severe clinical signs of mycoplasmosis on beaks and nares compared to tortoises with negative tests. Captive tortoises also exhibited significantly more clinical signs of illness than did wild tortoises, including lethargy and moderate to severe ocular signs. The severity of trauma and diseases of the shell and integument did not differ significantly among tortoises by site; however, clinical signs of moderate to severe trauma and disease were more prevalent in older tortoises. Similar to research findings for other species in the genus Gopherus in the US, we found that URTD is an important disease in captive tortoises. If they escape or are released by intention or accident to the wild, captive tortoises are likely to pose risks to healthy, naïve wild populations. © Wildlife Disease Association 2015.
Edwards T.,University of Arizona |
Karl A.E.,P.O. Box 74006 |
Vaughn M.,Paso Robles |
Rosen P.C.,University of Arizona |
And 2 more authors.
ZooKeys | Year: 2016
Desert tortoises (Testudines; Testudinidae; Gopherus agassizii group) have an extensive distribution throughout the Mojave, Colorado, and Sonoran desert regions. Not surprisingly, they exhibit a tremendous amount of ecological, behavioral, morphological and genetic variation. Gopherus agassizii was considered a single species for almost 150 years but recently the species was split into the nominate form and Morafka’s desert tortoise, G. morafkai, the latter occurring south and east of the Colorado River. Whereas a large body of literature focuses on tortoises in the United States, a dearth of investigations exists for Mexican animals. Notwithstanding, Mexican populations of desert tortoises in the southern part of the range of G. morafkai are distinct, particularly where the tortoises occur in tropical thornscrub and tropical deciduous forest. Recent studies have shed light on the ecology, morphology and genetics of these southern ‘desert’ tortoises. All evidence warrants recognition of this clade as a distinctive taxon and herein we describe it as Gopherus evgoodei sp. n. The description of the new species significantly reduces and limits the distribution of G. morafkai to desertscrub habitat only. By contrast, G. evgoodei sp. n. occurs in thornscrub and tropical deciduous forests only and this leaves it with the smallest range of the three sister species. We present conservation implications for the newly described Gopherus evgoodei, which already faces impending threats. © Taylor Edwards et al.
Hinojosa-Huerta O.,Pronatura Noroeste |
Soto-Montoya E.,Reserva de la Biosfera Alto Golfo de California y Delta del Rio Colorado |
Gomez-Sapiens M.,University of Arizona |
Calvo-Fonseca A.,Pronatura Noroeste |
And 4 more authors.
Ecological Engineering | Year: 2013
The Ciénega de Santa Clara is the largest marsh in the Sonoran Desert and the most important wetland in the Colorado River delta. We present the information on the state of the birds in the Ciénega and a checklist of the species that have been detected at the site. We also summarize the ornithological work that has been conducted and compiled recommendations for bird conservation. A total of 261 species of birds have been detected in the Ciénega de Santa Clara, representing 71% of the species known to the Colorado River delta. The birds of the Ciénega include 189 migratory species (70.4%), 49 year-round residents (18.7%), and 28 breeding visitors (10.7%). Twenty-seven species are federally protected in Mexico, four of them as Endangered, eight as Threatened, and 15 under Special Protection. The Ciénega provides critical habitat for migratory waterbirds, with maximum counts of 280,000 shorebirds in the southern mudflats, as well as for breeding marsh birds, including Yuma Clapper Rails, Virginia Rails and California Black Rails, with maximum estimates of 8600, 7150 and 400 individuals respectively. Other species of concern that occur regularly in the Ciénega include Least Bittern, Snowy Plover, Least Tern, and Large-billed Savannah Sparrow. This wetland also provides important stopover habitat for 81 species of Neotropical migratory landbirds during their northbound spring migration, particularly for Wilson's Warbler, Swainson's Thrush, Yellow Warbler, Pacific-slope Flycatcher, and Willow Flycatcher. Binational cooperation is essential to protect the Ciénega in the long-term, especially in terms of dedicating the necessary water for its maintenance. Active management actions are also becoming an important part of habitat conservation, including land protection mechanisms, sediment removal, and fire management. © 2013 Elsevier B.V.