Objectives



1. To identify species that aggregate to spawn within the WCB and to
describe (e.g. location, size, timing, nature) the aggregations of key
demersal species such as pink snapper and dhufish.



2. To investigate the biology, ecology and fishery for Samson fish with
emphasis on the sportsfishery targeting deep water spawning
aggregations west of Rottnest Island.



3. To establish methods and protocols for monitoring fish aggregations within the WCB.



4. To review relevant information and provide advice on the impact of
aggregation fishing and the management of aggregating fish species in
WA (with specific advice for key species within the WCB).

Conclusion:- The project has met its four main objectives. It
has utilised information from various sources including anecdotal
evidence, biological information, direct observations, commercial catch
and effort data and trialled many varied monitoring methods to identify
22 species of fisheries importance within the WCB that are known to or
suspected of forming spawning aggregations.



For the main species further information is provided on the location,
size, timing and nature of spawning aggregations, past and present. The
project has focussed on WA dhufish and Samson fish for which much new
and important information on their ecology and reproductive biology has
been discerned.



The Samson Science community involvement study of the spawning
aggregations of Samson fish in the metropolitan area has been widely
regarded as a successful example of the partnership of recreational
fishers and researchers. The information on spawning aggregations can
be utilised in future stock assessments of these species to account for
the influence that aggregation spawning can have upon the results from
these models, which will be utilised in their future management.



Finally as the project has undertaken a thorough assessment of various
potential monitoring techniques for spawning aggregations it has
provided recommendations on those suitable for each key species within
the WCB.



The study has collected evidence from various sources that validate the
formation of spawning aggregations by WA Dhufish. It has established
the importance of the Capes region with evidence of dhufish forming
large spawning aggregations in the past but also indicated that
spawning and other aggregations can occur, often to lesser degree,
elsewhere within the WCB.



The commercial catch and effort data revealed commercial fishers are
getting higher catch rates through the targeting of spawning
aggregations in these same areas.



The study has given a further insight into the ecology of the species
and shown how the spawning behaviour is complex with 1 large male often
having a harem of 3 to 8 females at a particular site during the
spawning period. The finding of atresia in the gonads of smaller mature
females on a number of occasions indicates there is some competition
between females for the attention of the males, further illustrating
the complexity of their spawning.



The Samson science component of the project .... tag and recapture
results indicate that fish predominantly come from the south coast and
from as far away as Kangaroo Island in SA, a distance of over 2000
kilometres, to the spawning aggregations west of Rottnest Island, which
has large implications to the importance of these aggregations for the
species.



The mechanism that allows this family of fish to “self vent” when
dealing with barotrauma situations has been identified and further
study of this by short term survival studies has validated the
assumption that most (90%) of the fish survive the capture and release,
even from depths of up to 195 m.



This indicates that if the fish are treated correctly, following the
protocols, the catch and release sportsfishery can operate on these
aggregations of such importance.....