Wild zebrafish exhibit a wide range of behavior. We found abundant wild zebrafish in flowing rivers and still water, in large, tightly-knit groups of hundreds of individuals, as well as in small, loose shoals. In two still-water populations, zebrafish were quite small in body size, common, and in tight groups of up to 22 fish. As in earlier laboratory studies, these zebrafish exhibited very low levels of aggression. In slowly flowing water in central India, zebrafish were relatively rare and gathered in small shoals (4-12 fish), often with other small fish, such as Rasbora daniconius. These stream zebrafish were larger in body size (27 mm TL) and much more aggressive than those in still water. In a second river population with much faster flowing water, zebrafish were abundant and again relatively large (21 mm TL). These zebrafish occurred in very large (up to 300 individuals) and tightly-knit (nearest-neighbor distances up to 21 mm) groups that exhibited collective rheotaxis and almost no aggression. This remarkable variation in social behavior of wild zebrafish offers an opportunity for future studies of behavioral genetics, development, and neuroscience.

rowing protests to decry police brutality and anti-Black racism have demanded sustained efforts for justice in the wake of the murders of Rayshard Brooks, George Floyd, Ahmaud Arbery and Breonna Taylor. Such injustices come at an especially challenging time in which Black communities are disproportionately being ravaged by the global COVID-19 pandemic 1,2 . These compounding issues have culminated in a watershed moment, in which non-Black colleagues, some for the first time, are beginning to legitimately grapple with the pervasive and pernicious nature of anti-Black racism embedded in our institutions and professions.Many scientific institutions, professional societies and individuals have swiftly and emphatically denounced anti-Black racism, pledging Black Lives Matter and acknowledging their support in deconstructing racial oppression and white supremacy in the academy. This support has largely come in the form of public statements and editorials that elevate Black voices, most notably from prestigious scientific outlets like Nature 3,4 and Science 5-7 . A recent editorial in Nature Ecology & Evolution 8 pledges to dismantle anti-Black racism in the annals of life sciences, which is a necessary step. But let us be clear: this is not enough and not even the minimum 9,10 . The road to anti-racism in academia is a long, arduous, uphill climb that will require institutional and personal reconciliation, resolve, discomfort and humility 11 . It is both necessary and urgent to promote inclusive excellence and transformative scholarship.Black scholars in the life sciences are grieving, traumatized, exhausted, infuriated, frustrated and experiencing many other disparaging emotions 4,12 . As we attempt to operate in a system that presents extraordinary barriers to our success, we also watch our white counterparts thrive

The formations made by gregarious animals can range from loose aggregates to highly synchronized and ordered structures. For very large, coordinated groups, both physical and social environments are important for determining the physical arrangement of individuals in the group. Here we tested whether physical and social factors are also important in determining the structure of small, loosely coordinated groups of zebrafish. We found that even though our fish were not crowded and did not use most of the available space, the distance between individual fish was explained primarily by the amount of available space (i.e., density). Zebrafish in a larger space spread out more and the total dimensions of the shoal were an additive function also of group size. We, however, did not find any impact of social or physical environment on the orientation of individual fish or shoal. Thus, both physical and social factors were important for shoal spatial arrangements, but not individual orientation and shoal alignment.

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