Influence of Benthic Macrofauna as a Spatial Structuring Agent for Juvenile Haddock (Melanogrammus aeglefinus) on the Eastern Scotian Shelf, Atlantic Canada.

Beatriz Rincón,Ellen L Kenchington,Hideyuki Doi

doi:10.1371/journal.pone.0163374

Beatriz Rincón, Ellen L Kenchington + Show 1 more

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https://doi.org/10.1371/journal.pone.0163374

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Abstract

We examined the habitat of juvenile haddock on the eastern Scotian Shelf (off Nova Scotia, Canada) in relation to grab-sampled benthic macrofaunal invertebrate species assemblages in order to determine whether there were significant differences in benthic macrofauna between areas of historically persistent high and low juvenile haddock abundance. Our analyses were conducted over two spatial scales in each of two years: among banks (Emerald, Western and Sable Island), approximately 60 km distant from each other, and between areas of high and low juvenile haddock abundance at distances of 10 to 30 km–all in an area that had not experienced groundfishing in the decade prior to sampling. We also examined fine-scale (10s of metres) within-site variability in the macrofauna and used surficial sediment characteristics, along with hydrographic variables, to identify environmental correlates. PERMANOVA identified statistically significant differences in biomass, density and composition of the benthos associated with juvenile haddock abundance; however it was difficult to determine whether the results had biological relevance. Post hoc tests showed that these differences occurred only on Sable Island Bank where both fish and benthos may have been independently responding to sediment type which was most different there (100% sand in the area of low haddock abundance vs. 22% gravel in the area of high haddock abundance). In total, 383 benthic taxa representing 13 phyla were identified. Annelida was the most specious phylum (36.29% of taxa, representing 33 families), followed by Arthropoda (with Crustaceans, mostly Amphipoda, accounting for 25.07% of the total number of taxa). The strongest pattern in the macrofauna was expressed at the largest scale, between banks, accounting for approximately 25% of the variation in the data. Emerald Bank, deeper, warmer and saltier than the Western and Sable Island Banks, had a distinctive fauna.

Highlights

As in other vertebrates, the spatial structure of fish populations is shaped both by factors endogenous to the populations and by habitat heterogeneity [1]
We examined the habitat of juvenile haddock on the eastern Scotian Shelf in relation to grab-sampled benthic macrofaunal invertebrate species assemblages in order to determine whether there were significant differences in benthic macrofauna between areas of historically persistent high and low juvenile haddock abundance
Polychaetes and amphipods prevailed in abundance with 10 to 13 species accounting for 50% of the total, whereas bivalves and echinoderms prevailed in biomass, with 4 to 7 species accounting for 90% of the total

Summary

Introduction

The spatial structure of fish populations is shaped both by factors endogenous to the populations and by habitat heterogeneity [1]. Currents and water masses play major roles in determining fish distributions at large spatial scales (100s of kms), while smaller-scale structure is often attributed to endogenous behavioral responses [2,3,4,5,6,7,8,9]. Heterogeneities of seabed habitat, both biotic and abiotic, have generally been under-studied as a spatial-structuring agent for boreal fishes living on continental shelves. Exceptions include those species that clearly utilize particular habitats for spawning (e.g., herring Clupea harengus) or burrowing (e.g., sand eels Ammodytes spp.). Benthic invertebrates are known to provide food [10,11,12,13], while biotic and abiotic benthic habitat can provide refuge [10,14]

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