76
M. Holmer et al.
2.3.3 Environmental Monitoring of Tuna Penning Activities
As part of the permit conditions issued by MEPA for tuna penning activities, the
farm operators were required to commission a comprehensive environmental monitoring programme to be carried out by independent consultants approved by
MEPA. Since the environmental characteristics at the tuna penning sites were very
different from those of the near-shore sites where sea bass and sea bream farms
were located, while the type and scale of operations were also very different, it was
immediately realised that MEPA’s environmental monitoring guidelines contained
in the 1994 PDGF could only be applied to tuna farms following modification.
Given the circumstances, in 2001 MEPA amended the 1994 PDGF such that the
revised guidelines stated that no aquaculture development would be considered in
areas less than 1 nautical mile from the shore, or in sites having a water depth less
than 50 m (give or take 5 m) (Planning Authority 2001).
In granting development permits for tuna-penning activities, MEPA requested
that monitoring of tuna penning activities should include monitoring of: (1) sediment attributes; (2) benthic diversity; (3) the gross physical and biological characteristics of the seabed below the tuna cages through underwater videography;
(4) the state of seagrass beds and of biological characteristics at important dive
sites located in the vicinity of the farms using underwater mapping and videography (in some cases, even if these were present at distances exceeding several hundred metres from the tuna cages); and (5) water quality. The specific requirements
for environmental monitoring of aquaculture operations in the PDGF of 2001 are
given in Table 2.7. The environmental monitoring programmes for all tuna farms
were initiated in 2000 and are still ongoing.
Samples to monitor sediments and benthic diversity have been collected annually (since 2000) at each tuna farm from a number of stations located: (1) adjacent
to the tuna-pens, (2) at a distance of some 100 m from the tuna pens, and (3) at a
number of reference sites; the sampling programme being mainly based on a
Before-After-Control-Impacted (BACI) design (Borg and Schembri 2005). Using
this design, an adverse impact is deemed to have occurred if a significant change
(at the 0.05 level of significance) for one or more of the monitored attributes is
recorded between the baseline condition and that following the tuna penning activities. In the case of benthic diversity, this would be a significant decrease in the total
number of species and/or abundance of the selected indicator species.
Monitoring of the gross physical and biological characteristics of the seabed
below the tuna cages is being undertaken through surveys carried out by SCUBA
divers using direct observation and underwater videography. During initial surveys
of the seabed below the tuna cages, it was immediately realised that the main
impacts on the seabed resulted from the presence of large amounts of uneaten feed-fish
that accumulated on the seabed below the cages. However, the amount of feed-fish below
the cages varied greatly, even between cages within the same farm. It was therefore
considered appropriate to develop an index to enable an objective semi-quantitative
assessment of the amount of uneaten feed-fish present (Table 2.8).
M. Holmer et al.
2.3.3 Environmental Monitoring of Tuna Penning Activities
As part of the permit conditions issued by MEPA for tuna penning activities, the
farm operators were required to commission a comprehensive environmental monitoring programme to be carried out by independent consultants approved by
MEPA. Since the environmental characteristics at the tuna penning sites were very
different from those of the near-shore sites where sea bass and sea bream farms
were located, while the type and scale of operations were also very different, it was
immediately realised that MEPA’s environmental monitoring guidelines contained
in the 1994 PDGF could only be applied to tuna farms following modification.
Given the circumstances, in 2001 MEPA amended the 1994 PDGF such that the
revised guidelines stated that no aquaculture development would be considered in
areas less than 1 nautical mile from the shore, or in sites having a water depth less
than 50 m (give or take 5 m) (Planning Authority 2001).
In granting development permits for tuna-penning activities, MEPA requested
that monitoring of tuna penning activities should include monitoring of: (1) sediment attributes; (2) benthic diversity; (3) the gross physical and biological characteristics of the seabed below the tuna cages through underwater videography;
(4) the state of seagrass beds and of biological characteristics at important dive
sites located in the vicinity of the farms using underwater mapping and videography (in some cases, even if these were present at distances exceeding several hundred metres from the tuna cages); and (5) water quality. The specific requirements
for environmental monitoring of aquaculture operations in the PDGF of 2001 are
given in Table 2.7. The environmental monitoring programmes for all tuna farms
were initiated in 2000 and are still ongoing.
Samples to monitor sediments and benthic diversity have been collected annually (since 2000) at each tuna farm from a number of stations located: (1) adjacent
to the tuna-pens, (2) at a distance of some 100 m from the tuna pens, and (3) at a
number of reference sites; the sampling programme being mainly based on a
Before-After-Control-Impacted (BACI) design (Borg and Schembri 2005). Using
this design, an adverse impact is deemed to have occurred if a significant change
(at the 0.05 level of significance) for one or more of the monitored attributes is
recorded between the baseline condition and that following the tuna penning activities. In the case of benthic diversity, this would be a significant decrease in the total
number of species and/or abundance of the selected indicator species.
Monitoring of the gross physical and biological characteristics of the seabed
below the tuna cages is being undertaken through surveys carried out by SCUBA
divers using direct observation and underwater videography. During initial surveys
of the seabed below the tuna cages, it was immediately realised that the main
impacts on the seabed resulted from the presence of large amounts of uneaten feed-fish
that accumulated on the seabed below the cages. However, the amount of feed-fish below
the cages varied greatly, even between cages within the same farm. It was therefore
considered appropriate to develop an index to enable an objective semi-quantitative
assessment of the amount of uneaten feed-fish present (Table 2.8).