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Marine Biology (2021) 168:165
https://doi.org/10.1007/s00227-021-03974-0
ORIGINAL PAPER
Historical trophic ecology ofsome divergent shark andskate species
intheDutch coastal North Sea zone
SuzanneS.H.Poiesz1,2 · TomasvanElderen1· JohannesIJ.Witte1· HenkW.vanderVeer1
Received: 29 October 2020 / Accepted: 30 September 2021 / Published online: 22 October 2021
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021
Abstract
Over the last century the fish community of the Dutch coastal North Sea zone has lost most its shark and skate species.
Whether their disappearance has changed the trophic structure of these shallow waters has not been properly investigated. In
this study historical dietary data of sharks and skates, being in the past (near)-residents, juvenile marine migrants and marine
seasonal visitors of the Dutch coastal North Sea zone were analyzed for the period 1946–1954. Near-resident and juvenile
marine migrant species were demersal while all marine seasonal visitors species were pelagic. Based on stomach content
composition, the trophic position of four of the various shark and skate species could be reconstructed. The (near)-resident
species, the lesser spotted dogfish, the marine juvenile migrant, the starry smooth hound, and the benthopelagic marine
seasonal visitor, the thornback ray, had a benthic/demersal diet (polychaetes, molluscs and crustaceans), while the pelagic
marine seasonal visitor, the tope shark, fed dominantly on cephalopods and fishes. Diet overlap occurred for fish (tope shark
and lesser spotted dogfish), for hermit crabs (lesser spotted dogfish and starry smooth hound) and for shrimps (thornback
ray and starry smooth hound). Trophic position ranged from 3.2 for thornback ray preying exclusively on crustaceans to 4.6
for the tope shark consuming higher trophic prey (crustaceans and fish). The analysis indicates that most of the shark and
skate species were generalist predators. The calculated trophic positions of shark and skate species indicate that those spe-
cies were not necessarily at the top of the marine ecosystem food web, but they might have been the top predators of their
particular ecological assemblage.
Keywords Historical trophic ecology· Dutch coastal North Sea zone· Food web reconstruction· Historical dietary data·
Predator–prey interactions· Sharks and rays· Trophic positions
Introduction
Worldwide, major structural and functional changes have
occurred in coastal ecosystems due to overfishing (Pauly
etal 1998; Jackson etal 2001; Lotze 2005). Pauly etal
(1998) state that this so-called “fishing down the marine
food web” reflects the removal of long-lived, high trophic
level, piscivorous fish, including sharks and skates. It is
unclear what effect the removal of top predators can have
on the stability of a community (Shurin etal 2002), because
for instance the relationship between food chain stability
and food chain length is unclear (Sterner etal 1997). While
it is easy to predict that carnivores have a high trophic posi-
tion and exert a degree of top-down effects, these effects are
still very poorly understood (Cortés 1999). Consequences
of the removal of top predators could have a cascading
effect down the food web, through to lower trophic posi-
tions such as bivalves and polychaetes (Hussey etal 2015).
These cascades potentially could extend to the level of the
primary producers (Myers etal 2007). Considering these
possible consequences, eliminating larger predators carries
more risks of broader ecosystem degradation than previously
thought. Top down effects must be widely expected when-
ever entire groups of predators are eliminated or removed.
Responsible Editor: C. Harrod.
* Suzanne S. H. Poiesz
suzanne.poiesz@nioz.nl
1 Department ofCoastal Systems, NIOZ Royal Netherlands
Institute forSea Research, Den Burg, P.O. Box59,
1790ABTexel, TheNetherlands
2 Faculty ofScience andEngineering, Groningen Institute
ofEvolutionary Life Sciences, University ofGroningen,
P.O. Box11103, 9700CCGroningen, TheNetherlands
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