Fish, People, and Systems of Power: Understanding and Disrupting Feedback between Colonialism and Fisheries Science.

AbstractThis essay explores shifting scientific understandings of fish and the evolution of fisheries science, and it grapples with colonialism as a system of power. We trace the rise of fisheries science to a time when Western nation-states were industrializing fishing fleets and competing for access to distant fishing grounds. A theory of fishing called "maximum sustainable yield" (MSY) that understands fish species in aggregate was espoused. Although alternatives to MSY have been developed, decision-making continues to be informed by statistical models developed within fisheries science. A challenge for structured management systems now rests in attending to different systems of knowledge and addressing local objectives, values, and circumstances. To deepen and illustrate key points, we examine Pacific herring (Clupea pallasii) and the expansion of commercial herring fisheries and state-led management in British Columbia, Canada. A feedback between colonialism and fisheries science is evident: colonialism generated the initial conditions for expansion and has been reinforced through the implementation of approaches and tools from fisheries science that define and quantify conservation in particular ways. Some features may be unique to the herring illustration, but important aspects of the feedback are more broadly generalizable. We propose three interconnected goals: (a) transform the siloed institutions and practices of Western science, (b) reimagine and rebuild pathways between information (including diverse values and perspectives) and decision-making, and (c) devolve governance authority and broaden governance processes such that multiple ways of knowing share equal footing.

Trophic control of cryptic coralline algal diversity.

Understanding how trophic dynamics drive variation in biodiversity is essential for predicting the outcomes of trophic downgrading across the world's ecosystems. However, assessing the biodiversity of morphologically cryptic lineages can be problematic, yet may be crucial to understanding ecological patterns. Shifts in keystone predation that favor increases in herbivore abundance tend to have negative consequences for the biodiversity of primary producers. However, in nearshore ecosystems, coralline algal cover increases when herbivory is intense, suggesting that corallines may uniquely benefit from trophic downgrading. Because many coralline algal species are morphologically cryptic and their diversity has been globally underestimated, increasing the resolution at which we distinguish species could dramatically alter our conclusions about the consequences of trophic dynamics for this group. In this study, we used DNA barcoding to compare the diversity and composition of cryptic coralline algal assemblages at sites that differ in urchin biomass and keystone predation by sea otters. We show that while coralline cover is greater in urchin-dominated sites (or "barrens"), which are subject to intense grazing, coralline assemblages in these urchin barrens are significantly less diverse than in kelp forests and are dominated by only 1 or 2 species. These findings clarify how food web structure relates to coralline community composition and reconcile patterns of total coralline cover with the widely documented pattern that keystone predation promotes biodiversity. Shifts in coralline diversity and distribution associated with transitions from kelp forests to urchin barrens could have ecosystem-level effects that would be missed by ignoring cryptic species' identities.

Sympatric kelp species share a large portion of their surface bacterial communities.

Kelp forest ecosystems are biodiversity hotspots, providing habitat for dense assemblages of marine organisms and nutrients for marine and terrestrial food webs. The surfaces of kelps support diverse microbial communities that facilitate the transfer of carbon from algal primary production to higher trophic levels. We quantified the diversity of bacteria on the surfaces of eight sympatric kelp species from four sites in British Columbia. Kelp-associated bacterial communities are significantly different from their environment, even though 86% of their bacterial taxa are shared with seawater and 97% are shared with rocky substrate. This differentiation is driven by differences in relative abundance of the bacterial taxa present. Similarly, a large portion of bacterial taxa (37%) is shared among all eight kelp species, yet differential abundance of bacterial taxa underlies differences in community structure among species. Kelp-associated bacterial diversity does not track host phylogeny; instead bacterial community composition is correlated with the life-history strategy of the host, with annual and perennial kelps supporting divergent bacterial communities. These data provide the first community-scale investigation of kelp forest-associated bacterial diversity. More broadly, this study provides insight into mechanisms that may structure bacterial communities among closely related sympatric host species.

Sudden collapse of a mesopredator reveals its complementary role in mediating rocky reef regime shifts.

While changes in the abundance of keystone predators can have cascading effects resulting in regime shifts, the role of mesopredators in these processes remains underexplored. We conducted annual surveys of rocky reef communities that varied in the recovery of a keystone predator (sea otter, Enhydra lutris) and the mass mortality of a mesopredator (sunflower sea star, Pycnopodia helianthoides) due to an infectious wasting disease. By fitting a population model to empirical data, we show that sea otters had the greatest impact on the mortality of large sea urchins, but that Pycnopodia decline corresponded to a 311% increase in medium urchins and a 30% decline in kelp densities. Our results reveal that predator complementarity in size-selective prey consumption strengthens top-down control on urchins, affecting the resilience of alternative reef states by reinforcing the resilience of kelp forests and eroding the resilience of urchin barrens. We reveal previously underappreciated species interactions within a 'classic' trophic cascade and regime shift, highlighting the critical role of middle-level predators in mediating rocky reef state transitions.