Correspondence/Amendment 5 Comments - New England Fishery ...

Z
ãt
ri':t:il
Role of egg predation by haddock in the decline
of an Atlantic herring population
David E. Richardson"'1, Jonathan A. Hare", Michaet J. Fogartyb, and Jason S. Linkb
"National Marine Fisheries Serv¡ce, Nât¡onal Oceanic and Atmospheric Administrat¡on, Narragansett, Rl 02882; and bNational Marine Fisheries Service,
Nat¡onal Oceanic and Atmospheric Admin¡stration, Woods Hole, MA 02543
Edited by John Beddington, lmperial College London, London, United Kingdom, and accepted by the Editor¡al Board July 5, 201 1 (received for review October
13,2010)
Theoretical studies suggest that the abrupt and substantial
changes ¡n the productivity of some lisheries species may be
explained by predation-driven alternate stable states in their
population levels. With this hypothesis, an increase in lishing or
a natural perturbat¡on can drive a population from an upper to
a lower stable-equilibrium population level. After flshing is reduced
or the perturbation ended, this low population level can
persist due to the regulatory effect of the predator. Although
established in theoretical studies, there is limited empirical support
for predation-driven alternate stable states in exploited marine
fish populations. We present evidence that egg predation by
haddock (Melanogrammus aeglefrnusl can cause alternate stable
population levels in Georges Bank Atlantic herring (Clupea harengus).
Egg predation by haddock explains a substantial decoupling
of herring spawning stock biomass (an index of egg production)
from observed larval herring abundance (an index of egg hatching),
Estimated egg survival rates ranged irom 98Vo. Overfrshing was clearly a primary driver behind the collapse
of these populations. However, the magnitude of the
population declines and, in some cases, the substantial delay in
recovery suggest that another mechanism was involved in these
population collapses. Part of the difficulty in identifing this
additional mechanism stems from the complexity of the herring
life cycle. Herring are migratory as juveniles and adults and
planktonic as larvae. Herring populations tend to be made up of
numerous subpopulations that mix during most of the year but
have discrete spawning locations (15, 16). At these spawning
Author contributions: D.E.R., J.A.H., M.J.F., and J.S.L. designed research; D.E.R., J.A.H.. and
J.5.1. performed reseârch; D.E.R. and J.5.1. analyzed data; and D.E.R. ând J.A.H. wrote the
papef.
The authors declâre no contl¡ct of interest.
Th¡s article is â PNAS Direct Submiss¡on. J.B. is ä guest ed¡tor invited by the Ed¡tor¡âl Board.
1To whom correspondence should be addressed. E-ma¡l: dav¡d.richardson@noâa.gov.
Th¡s art¡cle contå¡ns supporting ¡nformatìon online at w.pnas.org.¿læku/suppl/doi:10.
1 073/pnâs.1 01 5400'l 081/-/DCSupplemental.
PNAS Early Edit¡on I 1 of 6
g
c 3