Data from: Co-occurrence between size groups within populations decreases with maximum body size across marine fish populations

The degree of co-occurrence between size groups within a population
influences key biological processes, such as connectivity and competition
within a population. However, the links between co-occurrence between size
group pairs, abundance, and maximum body size among populations remain
largely unclear. In this study, we analyzed spatial time series data from
1982 to 2019 to investigate the co-occurrence between size groups of 54
marine fish populations across three regions (North Sea, Scottish West
Coast, and eastern Bering Sea). We show that for all the regions, the
probability of co-occurrence for most size group pairs decreased with
increasing maximum body size across populations. This suggests that the
size group pairs within larger-bodied populations tend to segregate more
in space, whereas those within smaller-bodied populations tend to mix and
aggregate. The co-occurrence for most size group pairs within populations
did not change with abundance, indicating that the tendency of the size
groups to aggregate or segregate was mostly insensitive to abundance.
Moreover, across populations and regions, the co-occurrence-abundance
relationship of most size group pairs did not change with the maximum body
size, except five size group pairs in the North Sea, suggesting that
compared to smaller-bodied populations, these size group pairs within
larger-bodied populations in this region tend to aggregate more with
increasing abundance and segregate more with decreasing abundance. These
findings provide new insights into the spatial dynamics of size groups,
offering valuable implications for understanding population spatial
structure and connectivity in marine ecosystems.