Abstract
Small-bodied marine fishes play an important role in the food web, feeding both larger fishes and seabirds. Often referred to as baitfishes, they concentrate seasonally in coastal areas in large, often heterospecific assemblages that are targeted by both commercial and recreational fishers. Given apparent declines in at least some of Bermuda’s baitfish species over the past 40 years, it is useful to determine the species composition of baitfish assemblages, and how it varies among sites, in order to inform management. Using genetic barcoding of the Cytochrome c oxidase 1 gene (COI), we confirm species identity, assess intraspecific genetic diversity locally, and determine rates of broader genetic connectivity for baitfish assemblages in Bermuda. Species analyzed included Hypoatherina harringtonensis, Anchoa choerostoma, Jenkinsia lamprotaenia, Harengula humeralis, Opisthonema oglinum and Sardinella aurita. Species identification based on molecular barcoding revealed some misidentification of individuals based solely on gross morphological characteristics, with an error rate of 11%, validating the usefulness of this approach. Interestingly, sequence results for the endemic Bermuda anchovy, A. choerostoma, were within 1% similarity to the more broadly distributed big-eye anchovy, A. lamprotaenia, and thus additional analyses are warranted to evaluate the genetic basis for endemism. Estimates of genetic diversity within and among baitfish assemblages in Bermuda were high, indicating high rates of local connectivity among sites for all species. As such, management should consider Bermuda’s baitfish species as single, highly mixed populations. However, with the exception of H. humeralis and the endemic A. choerostoma, significant genetic differentiation and population structure were found when comparing Bermuda’s baitfish populations with those from other regions, suggesting limited gene flow between other regions and Bermuda for these species. Limited regional connectivity has implications for management, as strong genetic divergence suggests that populations in Bermuda are predominantly self-seeding and thus not likely to be replenished from distant populations. These results therefore support precautionary management of baitfish species in Bermuda.
Highlights
Small-bodied, shoaling marine fishes are a critical part of the food chain, connecting plankton at low trophic levels to higher trophic level organisms such as seabirds and piscivorous fishes (Smith et al, 2011; Pikitch et al, 2014)
One sample from Frank’s Bay and one sample from Coney Island were identified as Hypoatherina harringtonensis, but the resulting sequences matched that of Jenkinsia lamprotaenia
c oxidase gene (COI) sequences of individuals morphologically identified as the endemic Bermuda anchovy, Anchoa choerostoma, had a 99% identity match (93% query coverage) to the widespread Atlantic species A. lamprotaenia
Summary
Small-bodied, shoaling marine fishes are a critical part of the food chain, connecting plankton at low trophic levels to higher trophic level organisms such as seabirds and piscivorous fishes (Smith et al, 2011; Pikitch et al, 2014). These species form large aggregations in coastal areas, and here they are targeted by both commercial and recreational fishers (Smith-Vaniz, Collette & Luckhurst, 1999; Smith et al, 2011). In Bermuda, large, heterospecific baitfish aggregations typically include several morphologically similar species from the families Clupeidae, Engraulidae, Atherinidae, and Hemiramphidae (Parrish, 1989; Smith-Vaniz, Collette & Luckhurst, 1999). Clupeidae] (Smith-Vaniz, Collette & Luckhurst, 1999; Lavoué, Konstantinidis & Chen, 2014)
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