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Bronwyn M. Gillanders
collected in Sri Lanka for the ornamental fish trade
and Epinephelus tauvina (Serranidae) is exported to
south-east Asia for fattening (Pinto and Punchihewa,
1996). In Sri Lanka, collecting fish and invertebrates
is thought to damage seagrass habitat; restrictions on
collecting organisms do not exist (Pinto and Punchihewa, 1996), and the effect of these activities on fish
stocks is unknown.
Aquaculture ventures, in particular fish farming,
may also affect the distribution of seagrass in some
areas, largely due to organic wastes that are released into the water column (Delgado et al., 1999;
Cancemi et al., 2003). For example, Ruiz et al. (2001)
found that since the onset of fish farming 53% of
the former seagrass meadow (Posidonia oceanica)
had either been completely lost or significantly degraded. In another study, although fish farming at
one site had ceased, seagrass decline persisted possibly due to excess organic matter in the sediment
(Delgado et al., 1999). Further studies are needed
on the impacts of fish farming on seagrasses.
Some indirect effects of fisheries on seagrass habitats include propeller scarring by boats navigating to
and from fishing operations, trampling of seagrass
(e.g. hand raking for clams), raising turbidity levels, and altering sediment type. The abundance and
size distribution of pinfish (Lagodon rhomboides,
Sparidae) and pipefish (Syngnathus scovelli, Syngnathidae) did not differ between propeller-scarred
(characterized by up to 31% vegetation loss) and reference seagrass beds (Bell et al., 2002). Thus, in areas that have been moderately to intensively scarred,
loss of seagrass did not appear to affect populations
of fish (Bell et al., 2002). Similar results of no effect
were found for shrimp where scarring impacted up to
50% of the habitat (Bell et al., 2002). Large areas of
non-impacted seagrass in the vicinity of propellerscarred areas may provide an alternative habitat for
organisms. Propeller scarring may also have more of
an effect on sedentary and infaunal species. Further
research is required to determine whether the results
of Bell et al. (2002) are applicable to other areas.
C. Restoration of Seagrass and Fisheries
With continued loss of seagrass beds and potential implications of this habitat loss for fisheries resources, restoration of seagrass habitats could prove
important. Effective restoration of habitats depends
on planted or restored seagrass beds providing resources that are similar to natural beds (Fonseca
et al., 1990, 1996). Despite this, commonly used
indicators of seagrass recovery typically focus on
the seagrass itself (e.g. % cover) and fish and invertebrates may not be monitored. Although many
studies have shown that fish and crustaceans utilize
natural seagrass beds, remarkably few studies have
examined whether restored or created seagrass beds
provide important habitat and food resources for fish
species. Transplanted, recently seed-colonized, and
natural beds of seagrass showed similar numbers and
species of fish and shrimps within 2 years of planting (Fonseca et al., 1990, 1996). Areas that were
planted with seagrass were initially colonized by
adults and subsequently by recruitment of early life
history stages. Whether these results obtained for the
first 3 years since planting can be extrapolated across
greater temporal scales is unknown (Fonseca et al.,
1996). The abundance and species of animals (fish
and invertebrates) in restored areas and an unaffected
control site were similar but differed from a nearby
barren area that had never recovered (McLaughlin
et al., 1983).
In a natural experiment, the fishes of seagrasses
that recolonized around disposal islands (the latter were created when the Atlantic Intracoastal Waterway was dredged) and those of natural seagrass
beds were compared. Differences were found in
the fish assemblages of well established recolonized
meadows and natural meadows, whereas newly recolonized meadows and natural seagrass meadows
had similar assemblages (Brown-Peterson et al.,
1993). Members of schooling, mobile families of
fish (Clupeidae, Engraulidae, Atherinidae, Mugilidae) were more common in recolonized meadows,
whereas benthic, sedentary families (Syngnathidae,
Gobiidae) were more common in natural meadows (Brown-Peterson et al., 1993). Seagrass species
composition of the recolonized (characterized by
Halodule wrightii) and natural (composed of a mixture of H. beaudettei and Cymodocea filiformis)
meadows also differed, however, and this may have
caused differences in fish assemblages between the
two types of seagrass.
Growth, survival, and movement of organisms
have infrequently been investigated in restored seagrass areas (but see Kenworthy et al., Chapter 25;
Bell et al., Chapter 26). Some data from marsh habitats is available that shows no difference in growth
rates between restored and reference marshes and
that both types of marsh are utilized by young-ofthe-year fish (Miller and Able, 2002).
Bronwyn M. Gillanders
collected in Sri Lanka for the ornamental fish trade
and Epinephelus tauvina (Serranidae) is exported to
south-east Asia for fattening (Pinto and Punchihewa,
1996). In Sri Lanka, collecting fish and invertebrates
is thought to damage seagrass habitat; restrictions on
collecting organisms do not exist (Pinto and Punchihewa, 1996), and the effect of these activities on fish
stocks is unknown.
Aquaculture ventures, in particular fish farming,
may also affect the distribution of seagrass in some
areas, largely due to organic wastes that are released into the water column (Delgado et al., 1999;
Cancemi et al., 2003). For example, Ruiz et al. (2001)
found that since the onset of fish farming 53% of
the former seagrass meadow (Posidonia oceanica)
had either been completely lost or significantly degraded. In another study, although fish farming at
one site had ceased, seagrass decline persisted possibly due to excess organic matter in the sediment
(Delgado et al., 1999). Further studies are needed
on the impacts of fish farming on seagrasses.
Some indirect effects of fisheries on seagrass habitats include propeller scarring by boats navigating to
and from fishing operations, trampling of seagrass
(e.g. hand raking for clams), raising turbidity levels, and altering sediment type. The abundance and
size distribution of pinfish (Lagodon rhomboides,
Sparidae) and pipefish (Syngnathus scovelli, Syngnathidae) did not differ between propeller-scarred
(characterized by up to 31% vegetation loss) and reference seagrass beds (Bell et al., 2002). Thus, in areas that have been moderately to intensively scarred,
loss of seagrass did not appear to affect populations
of fish (Bell et al., 2002). Similar results of no effect
were found for shrimp where scarring impacted up to
50% of the habitat (Bell et al., 2002). Large areas of
non-impacted seagrass in the vicinity of propellerscarred areas may provide an alternative habitat for
organisms. Propeller scarring may also have more of
an effect on sedentary and infaunal species. Further
research is required to determine whether the results
of Bell et al. (2002) are applicable to other areas.
C. Restoration of Seagrass and Fisheries
With continued loss of seagrass beds and potential implications of this habitat loss for fisheries resources, restoration of seagrass habitats could prove
important. Effective restoration of habitats depends
on planted or restored seagrass beds providing resources that are similar to natural beds (Fonseca
et al., 1990, 1996). Despite this, commonly used
indicators of seagrass recovery typically focus on
the seagrass itself (e.g. % cover) and fish and invertebrates may not be monitored. Although many
studies have shown that fish and crustaceans utilize
natural seagrass beds, remarkably few studies have
examined whether restored or created seagrass beds
provide important habitat and food resources for fish
species. Transplanted, recently seed-colonized, and
natural beds of seagrass showed similar numbers and
species of fish and shrimps within 2 years of planting (Fonseca et al., 1990, 1996). Areas that were
planted with seagrass were initially colonized by
adults and subsequently by recruitment of early life
history stages. Whether these results obtained for the
first 3 years since planting can be extrapolated across
greater temporal scales is unknown (Fonseca et al.,
1996). The abundance and species of animals (fish
and invertebrates) in restored areas and an unaffected
control site were similar but differed from a nearby
barren area that had never recovered (McLaughlin
et al., 1983).
In a natural experiment, the fishes of seagrasses
that recolonized around disposal islands (the latter were created when the Atlantic Intracoastal Waterway was dredged) and those of natural seagrass
beds were compared. Differences were found in
the fish assemblages of well established recolonized
meadows and natural meadows, whereas newly recolonized meadows and natural seagrass meadows
had similar assemblages (Brown-Peterson et al.,
1993). Members of schooling, mobile families of
fish (Clupeidae, Engraulidae, Atherinidae, Mugilidae) were more common in recolonized meadows,
whereas benthic, sedentary families (Syngnathidae,
Gobiidae) were more common in natural meadows (Brown-Peterson et al., 1993). Seagrass species
composition of the recolonized (characterized by
Halodule wrightii) and natural (composed of a mixture of H. beaudettei and Cymodocea filiformis)
meadows also differed, however, and this may have
caused differences in fish assemblages between the
two types of seagrass.
Growth, survival, and movement of organisms
have infrequently been investigated in restored seagrass areas (but see Kenworthy et al., Chapter 25;
Bell et al., Chapter 26). Some data from marsh habitats is available that shows no difference in growth
rates between restored and reference marshes and
that both types of marsh are utilized by young-ofthe-year fish (Miller and Able, 2002).