Predator-prey interaction study reveals more food does not always mean
more consumption

Date:
September 30, 2020
Source:
NOAA Northeast Fisheries Science Center
Summary:
Decades of data allow researchers to look at predator-prey
interactions in a different way: among multiple species throughout
the water column.

They have developed an unusually rich picture of who is eating
whom off the Northeastern United States.



FULL STORY ========================================================================== Scientists at the NOAA Northeast Fisheries Science Center have developed
an unusually rich picture of who is eating whom off the Northeastern
United States. The findings, published recently in Fish and Fisheries,
provide a close look at fish feeding habits for 17 fish species,
predators, and their prey.


==========================================================================
The predators are divided into 48 predator-size categories, and 14 prey species. Fish predators included Atlantic cod, Atlantic herring, haddock, goosefish, pollock, spiny dogfish, winter flounder, and yellowtail founder among others. Prey species included forage fish, squid, zooplankton,
shrimp- like crustaceans, shellfish, brittle stars, sand dollars, and
sea urchins.

"We have the largest, continuous dataset of fish feeding habits in the
world at the Northeast Fisheries Science Center, and that enabled us to
do a study of this scale and scope," said Brian Smith, a food habits
researcher at the center and lead author of the study. "We focused on
common and important prey for the many predatory fishes of interest, and hopefully filled in some gaps in information relating prey availability
to predation." Feeding patterns within and among different groups of
fishes vary by the size of the fish, the abundance or density of the prey,
and other factors.

Researchers who study marine ecosystems need to account for this predation
in their models. Few studies, however, have looked simultaneously at the feeding patterns among different groups of predatory fish -- fish feeders, plankton feeders, and benthic or bottom feeders. The study also looked
at how those groups interact with their prey throughout the water column.

Smith and co-author Laurel Smith tested three models using decades
of fisheries data that included diet and prey density. The data were
collected on the Northeast U.S. Continental Shelf during benthic surveys
in the 1950s and 1960s, and during ecosystem sampling surveys beginning
in 1973. For this study, the data were used to gain insight into:
* The relationship between the amount of prey available in the
environment * Consumption rates among multiple prey species *
Feeding patterns within and among different groups of fishes that eat
similar items.

Among the study findings: most of the fish responded to changing
abundance of prey by switching prey, or through a "learning period"
when the prey in highest abundance was targeted. That response helps
stabilize prey populations, and was prevalent among piscivores (fish
eaters). It was often observed for predators with less-specialized
feeding habits. Those predators included goosefish and larger sizes of
other well-known commercial fishes.

High densities of invertebrate prey, however, revealed decreased
feeding by fish that were planktivores and benthivores -- plankton
and bottom feeders. For these fish, more food did not translate to
more consumption. Researchers found that denser prey may disorient or
confuse the planktivores, reducing their feeding on zookplankton. The planktivores include Atlantic herring, Atlantic mackerel, and smaller
sizes of pollock, silver hake, spiny dogfish and white hake. Their
feeding response is not often considered in studies of marine ecosystems.

The benthivores studied included smaller sizes of Atlantic cod,
red hake, and winter skate, and all sizes of haddock, ocean pout, and
several flounders and a few other species. These fish ate small benthic invertebrates as small and medium-sized fish. Larger individuals of those
same species, however, ate mostly fish and had a different predator-prey relationship.

The study findings provide insight into predation on and by commercial
fishery species throughout the water column. This will help with ecosystem modeling since predation needs to be accounted for as competition,
or as a direct removal of commercially and ecologically important prey
species. Refining the model inputs can also increase our understanding of continental shelf ecology, and improve decision-making for ecosystem-based fisheries management.


========================================================================== Story Source: Materials provided by
NOAA_Northeast_Fisheries_Science_Center. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Brian E. Smith, Laurel A. Smith. Multispecies functional responses
reveal
reduced predation at high prey densities and varied responses
among and within trophic groups. Fish and Fisheries, 2020; 21 (5):
891 DOI: 10.1111/faf.12468 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200930085155.htm

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