Chapter 21
Seagrasses, Fish, and Fisheries
Bronwyn M. Gillanders
Southern Seas Ecology Laboratories, Darling Building DP418, School of Earth
and Environmental Sciences, University of Adelaide, SA 5005, Australia;
email: browyn.gillanders@adelaide.edu.au
I. Introduction
Seagrass meadows have extremely high primary
and secondary productivity and support a great
abundance and diversity of fish and invertebrates.
A number of commercially and recreationally important species (including both fish and invertebrates) have been linked to seagrass at some stage of
their life cycle, although few such species use seagrass throughout their life. Non-commercial species
within seagrass may be an important food source
for commercial species (forming trophic linkages).
In addition, some species that do not inhabit seagrass may derive benefit from seagrass by way of exported seagrass detritus or resident/transient species
that move out of seagrass (some of these topics are
dealt with elsewhere in this volume: e.g. Heck and
Orth, Chapter 22, Kenworthy et al., Chapter 25 and
Bell et al., Chapter 26).
A considerable amount of research on fish and invertebrates within seagrass meadows has been done,
including many fisheries-related aspects. Besides individual research papers, a number of reviews on
the ecology of fish assemblages and fisheries associated with seagrasses are available (e.g. Bell and
Pollard, 1989; Butler and Jernakoff, 1999; Jackson
et al., 2001). It is not my intention to duplicate these
reviews, but rather report on and synthesize recent
research that is contributing to our understanding of
the fauna of seagrass meadows. In this chapter, I use
the terms fish and fisheries broadly to encompass
both fish and invertebrates. I will briefly mention
the use of seagrass beds by fish species, which are
both temporary and permanent residents, but note
that this area has recently been covered in a review
by Jackson et al. (2001). I will compare the abundance, diversity, growth, and survival of fish in seagrass meadows with other nearshore habitats, but
again point the reader to a series of recent reviews
and meta-analyses that critically review the nursery
role hypothesis (sensu Beck et al., 2001) by comparing nearshore habitats to seagrass (Heck et al.,
2003), marsh (Minello et al., 2003), and mangrove
(Sheridan and Hays, 2003) habitats. I will then focus on patterns and potential mechanisms that may
contribute to spatial and temporal variation in abundances of fish in seagrass meadows. I will investigate
links between seagrass and fisheries with a focus
on new methods such as otolith chemistry and stable isotopes for determining such linkages. Finally,
I will investigate some of the conservation and management issues that pertain to seagrass habitats in
terms of their occupants (e.g. impacts due to fisheries and restoration of seagrass habitats in terms of
fish and fisheries).
II. Use of Seagrass Beds by Fish Species
Seagrass meadows provide shelter and food for assemblages of fish. Increased food availability to juveniles and protection from predators are often cited
as reasons why such large numbers of organisms
are associated with seagrass, but studies that actually evaluate whether more food is available are
scarce (Heck et al., 1997). Increased food is thought
to lead to increased growth rates, which in turn facilitates lower mortality rates (Bell and Pollard, 1989).
The structural complexity of seagrass habitats is also
thought to provide shelter from predators. In addition, seagrass beds often are located some distance
from reef habitats (rocky reef or coral reef) and offshore waters and therefore may have fewer predators.
Some of these issues, such as food vs. protection vs.
503–536.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.
Seagrasses, Fish, and Fisheries
Bronwyn M. Gillanders
Southern Seas Ecology Laboratories, Darling Building DP418, School of Earth
and Environmental Sciences, University of Adelaide, SA 5005, Australia;
email: browyn.gillanders@adelaide.edu.au
I. Introduction
Seagrass meadows have extremely high primary
and secondary productivity and support a great
abundance and diversity of fish and invertebrates.
A number of commercially and recreationally important species (including both fish and invertebrates) have been linked to seagrass at some stage of
their life cycle, although few such species use seagrass throughout their life. Non-commercial species
within seagrass may be an important food source
for commercial species (forming trophic linkages).
In addition, some species that do not inhabit seagrass may derive benefit from seagrass by way of exported seagrass detritus or resident/transient species
that move out of seagrass (some of these topics are
dealt with elsewhere in this volume: e.g. Heck and
Orth, Chapter 22, Kenworthy et al., Chapter 25 and
Bell et al., Chapter 26).
A considerable amount of research on fish and invertebrates within seagrass meadows has been done,
including many fisheries-related aspects. Besides individual research papers, a number of reviews on
the ecology of fish assemblages and fisheries associated with seagrasses are available (e.g. Bell and
Pollard, 1989; Butler and Jernakoff, 1999; Jackson
et al., 2001). It is not my intention to duplicate these
reviews, but rather report on and synthesize recent
research that is contributing to our understanding of
the fauna of seagrass meadows. In this chapter, I use
the terms fish and fisheries broadly to encompass
both fish and invertebrates. I will briefly mention
the use of seagrass beds by fish species, which are
both temporary and permanent residents, but note
that this area has recently been covered in a review
by Jackson et al. (2001). I will compare the abundance, diversity, growth, and survival of fish in seagrass meadows with other nearshore habitats, but
again point the reader to a series of recent reviews
and meta-analyses that critically review the nursery
role hypothesis (sensu Beck et al., 2001) by comparing nearshore habitats to seagrass (Heck et al.,
2003), marsh (Minello et al., 2003), and mangrove
(Sheridan and Hays, 2003) habitats. I will then focus on patterns and potential mechanisms that may
contribute to spatial and temporal variation in abundances of fish in seagrass meadows. I will investigate
links between seagrass and fisheries with a focus
on new methods such as otolith chemistry and stable isotopes for determining such linkages. Finally,
I will investigate some of the conservation and management issues that pertain to seagrass habitats in
terms of their occupants (e.g. impacts due to fisheries and restoration of seagrass habitats in terms of
fish and fisheries).
II. Use of Seagrass Beds by Fish Species
Seagrass meadows provide shelter and food for assemblages of fish. Increased food availability to juveniles and protection from predators are often cited
as reasons why such large numbers of organisms
are associated with seagrass, but studies that actually evaluate whether more food is available are
scarce (Heck et al., 1997). Increased food is thought
to lead to increased growth rates, which in turn facilitates lower mortality rates (Bell and Pollard, 1989).
The structural complexity of seagrass habitats is also
thought to provide shelter from predators. In addition, seagrass beds often are located some distance
from reef habitats (rocky reef or coral reef) and offshore waters and therefore may have fewer predators.
Some of these issues, such as food vs. protection vs.
503–536.
A. W. D. Larkum et al. (eds.), Seagrasses: Biology, Ecology and Conservation, pp.
c
2006 Springer. Printed in the Netherlands.