Vaquita Face Extinction from Bycatch. Comment on Manjarrez-Bringas, N. et al., Lessons for Sustainable Development: Marine Mammal Conservation Policies and Its Social and Economic Effects. Sustainability 2018, 10, 2185

We are among the scientists who have documented the environmental and ecological changes to the Upper Gulf of California following the reduction in the Colorado River&rsquo;s flow. We object to any suggestion that our research supports Manjarrez-Bringas et al.&rsquo;s conclusion that the decline in the Colorado River&rsquo;s flow is the reason for the decline in the population of the endangered vaquita porpoise (Phocoena sinus). Manjarrez-Bringas et al.&rsquo;s conclusions are incongruent with their own data, their logic is untenable, their analyses fail to consider current illegal fishing practices, and their recommendations are unjustified and misdirected. Vaquita face extinction because of bycatch, not because of the lack of river flow.</p

Comment on Rojas-Bracho and Colleagues (2019): Unsubstantiated Claims Can Lead to Tragic Conservation Outcomes

The vaquita’s decline is a tragic story indeed. However, the lack of action to prevent the extinction of this species is not due to unsubstantiated claims and scientific uncertainty

Vaquita Face Extinction from Bycatch. Comment on Manjarrez-Bringas, N. et al., Lessons for Sustainable Development: Marine Mammal Conservation Policies and Its Social and Economic Effects.

We are among the scientists who have documented the environmental and ecological changes to the Upper Gulf of California following the reduction in the Colorado River’s flow. We object to any suggestion that our research supports Manjarrez-Bringas et al.’s conclusion that the decline in the Colorado River’s flow is the reason for the decline in the population of the endangered vaquita porpoise (Phocoena sinus). Manjarrez-Bringas et al.’s conclusions are incongruent with their own data, their logic is untenable, their analyses fail to consider current illegal fishing practices, and their recommendations are unjustified and misdirected. Vaquita face extinction because of bycatch, not because of the lack of river flow

Isotopic Logs of The Sea of Cortez: Oxygen and Carbon Stable Isotopes in Otoliths of Marine Fish Record the Impact of Diverting the Colorado River from the Sea

I use microchemistry in fish otoliths to test the hypothesis that diverting Colorado River flow from reaching the Gulf of California has impacted two endemic fish: the threatened gulf Corvina, (Cynoscion othonopterus) and the endangered totoaba (Totoaba macdonaldi). The oxygen and carbon stable isotope ratios in otoliths help to reconstruct conditions of the environment during key life history stages before and after the damming and diverting the Colorado River. The δ¹⁸O in otoliths illustrate that both C. othonopterus and T. macdonaldi seek out brackish habitat provided by the Colorado River during their early life history. The δ¹⁸O of C. othonopterus otolith have a strong negative correlation with Colorado River flow. I found that previously published relationships between otolith δ¹⁸O and ambient temperature along with δ¹⁸O of the water are sufficient to predict ranges of expected δ¹⁸O values for T. macdonaldi in the field. The δ¹⁸O in pre-dam T. macdonaldi otoliths show significant divergence from modern T. macdonaldi otoliths’ values, indicating that these fish used the brackish waters of the Colorado River estuary. The δ¹³C in T. macdonaldi otoliths has a significant proportion of its δ¹³C derived from diet. Pre-dam T. macdonaldi juveniles have a significantly different diet, which reflects that the Colorado River estuary had higher productivity before diversion of the river. Lastly, T. macdonaldi grew faster before the dams and in association with Colorado River flow measured by the δ¹⁸O

A Story of Discovery: Revealing the Mysteries of Ancient Clam Gardens

Stories of discovery are rarely told despite being the origin of scientific innovation. Perhaps this is because discovery typically begins with failure, is often unexpected, and is exceedingly rare. Yet this is where scientific excitement begins and burgeons. By weaving together scientific experiments, with archeological data, traditional knowledge and ethnographic records, we will share our story of surprise, camaraderie and unexpected results en route to learning about how clam gardens work. Our discovery, or in this case re-discovery, revealed that ancient clam gardens have four times the number of butter clams and twice the number of littleneck clams compared to typical unmodified clam beaches. Furthermore, baby clams transplanted in to the sediment of these ancient intertidal gardens grew almost twice as fast and were more likely to survive than those transplanted in typical calm beaches. Something about these ancient gardens was unique and an experiment we thought would never work led us to one of the answers. We discovered that by reducing the slope of a beach, clam garden terraces expand clam habitat right at the optimal intertidal height at which clams grow and survive best. Moreover, a diversity of mariculture techniques and governance practices were used to increase and maintain the production of clams. Recent research has revealed that clam gardens were embedded within a diverse portfolio of resource use and management strategies that may have conferred resilience to past coastal communities by maintaining reliable access to diverse and productive food resources. Sustaining local and global food production, while maintaining resilient ecosystems, is one of the greatest environmental and humanitarian challenges of our time. Here, we share our story of discovery into how human ingenuity from the past can provide practical insights into marine conservation strategies that can support food security and sovereignty today

Ancient aquaculture practices in British Columbia: Clam gardens provide insights and baselines for today’s management

Maintaining food production while sustaining productive ecosystems is among the central challenges of our time, and it has been for millennia. In the Salish Sea and beyond, the ancient aquaculture strategy of constructing clam gardens, intertidal rock-walled terraces, is thought to have improved productivity of clams for coastal communities. The Clam Garden Network, a collaborative team of First Nations knowledge holders, archaeologists, and ecologists has been examining traditional marine resource management systems throughout the Northwest Coast. Our first ecological clam garden study on Quadra Island, BC takes a closer look at how clam gardens impact the productivity of subsistence clam species. We tested the hypothesis that clam gardens enhance clam productivity by comparing the beach slope, intertidal height, and biomass and density of bivalves at replicate clam gardens and non-walled clam beaches. We also quantified the variation in growth and survival rates of littleneck clams (Leukoma staminea) as we experimentally transplanted across these two beach types. We found that clam gardens had significantly shallower slopes and greater densities of L. staminea and Saxidomus giganteus. Overall, clam gardens contained 4 times as many butter clams and over twice as many little neck clams relative to non-walled beaches. Transplanted juvenile L. staminea grew 1.7 times faster and smaller size classes were more likely to survive in clam gardens. As predicted, these relationships varied as a function of intertidal height. Consequently, we provide strong evidence that ancient clam gardens likely increased clam productivity by altering the slope of soft-sediment beaches, expanding optimal intertidal clam habitat, thereby enhancing growing conditions for clams. These results reveal how ancient shellfish aquaculture practices may have supported food security strategies in the past and provide insight into tools for the conservation, management, and governance of intertidal seascapes today

Ancient Clam Gardens Increased Shellfish Production: Adaptive Strategies from the Past Can Inform Food Security Today

Maintaining food production while sustaining productive ecosystems is among the central challenges of our time, yet, it has been for millennia. Ancient clam gardens, intertidal rock-walled terraces constructed by humans during the late Holocene, are thought to have improved the growing conditions for clams. We tested this hypothesis by comparing the beach slope, intertidal height, and biomass and density of bivalves at replicate clam garden and non-walled clam beaches in British Columbia, Canada. We also quantified the variation in growth and survival rates of littleneck clams (Leukoma staminea) we experimentally transplanted across these two beach types. We found that clam gardens had significantly shallower slopes than non-walled beaches and greater densities of L. staminea and Saxidomus giganteus, particularly at smaller size classes. Overall, clam gardens contained 4 times as many butter clams and over twice as many littleneck clams relative to non-walled beaches. As predicted, this relationship varied as a function of intertidal height, whereby clam density and biomass tended to be greater in clam gardens compared to non-walled beaches at relatively higher intertidal heights. Transplanted juvenile L. staminea grew 1.7 times faster and smaller size classes were more likely to survive in clam gardens than non-walled beaches, specifically at the top and bottom of beaches. Consequently, we provide strong evidence that ancient clam gardens likely increased clam productivity by altering the slope of soft-sediment beaches, expanding optimal intertidal clam habitat, thereby enhancing growing conditions for clams. These results reveal how ancient shellfish aquaculture practices may have supported food security strategies in the past and provide insight into tools for the conservation, management, and governance of intertidal seascapes today

Map of Study Area.

<p>This research was conducted on A) the west coast of British Columbia, Canada, in the Inside Passage between B) Vancouver Island and the mainland on the northern end of C) Quadra Island, in Kanish Bay (West, starred) and Waiatt Bay (East, starred).</p

Survey & Experiment: <i>L. staminea</i> Biomass, Density and Growth by Intertidal Height vs. Model Predictions.

<p>Actual and predicted A&B) density (count/0.018 m3 +/− SE) C&D) biomass (kg/0.018 m3 +/− SE) and E) growth (mean +/−SE) of surveyed (A-D) and transplanted (E) <i>L. staminea</i> as a function of intertidal height (m above LLWLT) in clam gardens (green triangles) and non-walled beaches (blue circles) in Kanish and Waiatt bays, British Columbia, Canada.</p

Experimental effects of clam garden treatment and tidal station.

<p>The effects of clam gardens (Beach Type) and tidal station on the growth and survivorship of transplanted <i>L. staminea</i>. * designates significant p-values (p≤0.05).</p