Is what is there what you catch? 2008 update Baited Remote Underwater Video in the southern Great Barrier Reef

Transcription

1 Is what is there what you catch? 2008 update Baited Remote Underwater Video in the southern Great Barrier Reef

2 Is what is there what you catch? 2008 update Baited Remote Underwater Video in the southern Great Barrier Reef John Platten Capricorn Bunker Consulting 2/17 Bernard Street Rockhampton Qld 4701 Bill Sawynok Infofish Services PO Box 9793 Frenchville Qld 4701 Published July 2008 Cover photographs: (Top) CapReef Baited Remote Underwater Video unit about to be deployed (Bottom) Saddletail Snapper caught on camera in the green zone around Split Rock. Information in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. Infofish Services has taken all steps to ensure the information contained in this publication is accurate at the time of publication. Readers should ensure that they make the appropriate enquiries to determine whether new information is available on a particular subject matter. Report No: STCR Infofish Services and Capricorn Bunker Consulting All rights reserved. No part of this publication may be reprinted, reproduced, stored in a retrieval system or transmitted, in any form or by any means, without prior permission from Infofish Services. page 2

3 Table of Contents Acknowledgements... 4 About CapReef... 5 Fish Species... 6 Summary Introduction Objectives Methods Results Discussion References List of Figures and Tables Figure 1: Locations where BRUV video obtained at Keppel Bay sites Figure 2: Comparison of the number of fish observed in open and green zones Figure 3: Comparison of the proportion of sets where fish were observed in open and green sites Figure 4: Comparison of the proportion of each species observed to feed in open and green sites Figure 5: Comparison of the proportion of trips where each species was reported in the catch and the proportion of sets where the species was seen in open zoned sites Figure 6: Comparison of the proportion of trips where each species was reported in the catch and the proportion of sets where the species was seen in green zoned sites Figure 7: Trevally observed at Cape Capricorn Table 1: Names used in this report for key fish species... 6 Table 2: Percentage of species caught that are kept Table 3: Percentage of BRUV sets in open and green zones greater than percentage of trips catching species page 3

4 Acknowledgements The contribution of the following are acknowledged in relation to this project. Thanks go to the Fitzroy Basin Association and the Natural Heritage Trust for providing funding to CapReef. This allowed the CapReef team to establish a Baited Remote Underwater Video (BRUV) unit. Funding was also provided to CapReef in 2007/08 by the Recreational Fishing Community Grants Program of the Department of Agriculture, Fisheries and Forestry. Additional funding was also provided by the Great Barrier Reef Marine Park Authority (GBRMPA). Thanks to the GBRMPA for their support of CapReef and for providing the permit required to use the BRUV in the Marine Park, including Marine National Park Protection Zones (no fishing zones). Thanks to the Department of Defence for providing access to the Shoalwater Bay Training Area and to Kim Martin for his work in liaising with the Department. Without the support of the Department of Defence the collection of this data in Shoalwater Bay would not have been possible. page 4

5 About CapReef CapReef is a community based monitoring program that was established following a series of changes to management of the Great Barrier Reef (GBR). The purpose of CapReef is to improve community involvement and knowledge in management of the Capricorn part of the Great Barrier Reef ecosystem by monitoring and analysis of local effects of management changes on the GBR ecosystem. In recent years significant changes were made to management arrangements of the GBR. Major changes resulted from: Fisheries (East Coast Trawl) Management Plan 1999 Great Barrier Reef Marine Park Zoning Plan 2003 Great Barrier Reef Coast Marine Park 2004 Fisheries (Coral Reef Fin Fish) Management Plan 2003/04 As part of the consultation processes for the zoning changes in 2004 enforcement and monitoring emerged as significant community concerns. In response Capricorn Sunfish, GBRMPA Local Marine Advisory Committee and other interested groups developed the concept of a community based monitoring approach. This led to the birth of CapReef. A number of projects were established under CapReef to collect data on the effects of the management changes, particularly on fish and fishers. Thus CapReef is a repository for data being collected in the Capricorn part of the GBR and is a major contributor to a number of research projects. Projects to date have focused on: Coordinating CapReef and providing feedback to the community Measuring changes in catch and effort, relative abundance and size structure of key fish species Determining changes in fisher participation and fishing patterns resulting from the new Management Plans Obtaining information on the movement of key fish species from extended marine national park and conservation zones in the new Management Plans CapReef has also provided support for Coral Trout monitoring around the Keppel Islands by James Cook University, collection and identification of larval reef fish by the Central Queensland University and water quality sampling at Rosslyn Bay by the Australian Institute of Marine Science. An important part of CapReef is to provide feedback to the community a series of technical reports have been produced. This report is another in that series. page 5

6 Fish Species Fish names cause considerable confusion as there are many names that can be applied to the same fish species, even in the same region. The Australian Fish Names Committee has developed a list of standard names (Yearsley et al 2006). A copy of the Australian Fish Names List is available from CapReef uses the Standard Name for fish species in all reports. Standard Name Local Names Scientific Name Barcheek Coral Trout Common Coral Trout Coral Trout, Island Trout Coral Trout Plectropomous maculatus Plectropomous leopardus The identification of these two species is often confused by those inexperienced with the species Goldspotted Rockcod Blackspotted Rockcod Cod, Estuary Cod, Goldspot Cod Cod, Estuary Cod, Blackspot Cod Epinephelus coioides Epinephelus malabaricus These two species are collectively referred to as Estuary Cod however their identification should not be confused Longfin Rockcod Matty Cod, Wirenetting Cod Epinephelus quoyanus Saddletail Snapper Crimson Snapper Largemouth Nannygai, Red Jew Smallmouth Nannygai, Red Jew Lutjanus malabaricus Lutjanus erythropterus These two tropical Snapper species are collectively referred to as Red Jew and there is often confusion in their correct identification Red Emperor Red Emperor Lutjanus sebae Stripey Snapper Stripey Lutjanus carponatus Hussar Brownstripe Snapper Hussar Hussar Lutjanus adetii Lutjanus vitta These two species are collectively referred to as Hussar even though there is little confusion with their identity Venus Tuskfish Parrotfish Choerodon venustu Snapper Snapper, Pinkie Pagrus auratus Redthroat Emperor Redthroat, Sweetlip, Lipper Lethrinus miniatus Grass Emperor Grassy, Grass Sweetlip Lethrinus fletus Spangled Emperor Yellow Emperor, Yellow Lipper Lethrinus nebulosus Collar Seabream Iodine Bream, Baldy Bream Gymnocranius audleyi Rainbow Monocle Bream Paradise Threadfin Bream Bananafish, Whiptail Whiptail Scolopsis mongramma Pentapodus paradiseus Painted Sweetlips Blackall, Moke, Morwong Diagramma pictum Scribbled Rabbitfish Happy Moment, Spinefoot Siganus spinus Starry Triggerfish Triggerfish Abalistes stellaris Moon Wrasse Moon Wrasse, Wrasse Thalossoma lunare Table 1: Names used in this report for key fish species page 6

7 Summary This report is an update to and builds on the report by CapReef in July 2007 titled Is what is there what you catch? This document reported the results obtained from using Baited Remote Underwater Video (BRUV) to observe the fish attracted to bait across a range of locations within the CapReef area during 2007/08. The objectives of this report are: To examine the types fish that approach baits in green and open zones; To examine whether fish are more common than catch rates indicate by comparing catch information with the results from the BRUV as a fisheries independent means of examining fish numbers; To compare the number of fish approaching the baits in the open and green zones; and To compare the percentage of fish feeding on the BRUV bait within and outside the no fishing zones. Deployments of the BRUV were designed to allow comparison between open zones and closed green zones (Marine National Park). Sites were chosen across the CapReef area with locations from inshore to the Keppel Islands. Sites were: Pelican Island and Split Rock; Eastern North Keppel Island and Pumpkin Island; Barren Island and Egg Rock (2 occasions one set of deep and one of shallow sites); Miall and Middle Islands (2 occasions); 2 sites near Halfway Island (2 occasions); Cape Capricorn; and Shoalwater Bay. Overall 308 fish from 45 species were recorded from open zones and 263 fish from 42 species in green zones. Of the 17 species recorded in both the open and green zones. 211 fish were observed in open zones and 196 in green zones. Of the 17 species, 6 were observed more often in the open zones, 11 were observed more often in green zones. Four of the fish species were observed to feed more often in open zones, 13 in green zones. 42% of fish fed at the baits in open zones and 55% fed in green zones. The percentage of sets of the BRUV in open and green locations where species were observed was compared with the percentage of trips that caught the species. For the open zone, 4 species were observed more frequently in the catch records and 13 were observed more frequently in the open location BRUV sets. Overall, species targeted by fishers such as Coral Trout, Stripey Snapper, Venus Tuskfish and Saddletail Snapper were more numerous in green zones and more likely to feed on BRUV baits. page 7

8 Conversely species not targeted by fishers such as Starry Triggerfish, Monocle Bream, Collar Seabream and Remora were more common in open zones but still less likely to feed in the open zones. page 8

9 Is what is there what you catch? 2008 Update Baited Remote Underwater Video in the southern Great Barrier Reef 1. Introduction This report is an update to and builds on the report by CapReef in July 2007 titled Is what is there what you catch? This document reported the results obtained from using Baited Remote Underwater Video (BRUV) to observe the fish attracted to bait across a range of locations within the CapReef area during 2007/08. The 2007 report demonstrated that: Fish targeted by fishers were present in numbers in the CapReef area; A number of fish species that are seldom if ever caught are observed to feed on baits eg Angelfish; A number of species were probably more common than catch rates indicate eg Coral Trout; and Fish within no fishing (green) zones may be more likely to feed at baits than fish in areas open to fishing. The methods described in last year s report were repeated during 2007/08 to build on these results and to further clarify some issues raised. In particular this report examines and compares results obtained from open and green zone locations in a more controlled and structured fashion. 2. Objectives The objectives of this report are: To examine the types fish that approach baits in green and open zones; To examine whether fish are more common than catch rates indicate by comparing catch information with the results from the BRUV as a fisheries independent means of examining fish numbers; To compare the number of fish approaching the baits in the open and green zones; and To compare the percentage of fish feeding on the BRUV bait within and outside the no fishing zones. 3. Methods The details of the BRUV apparatus and the methods used in deploying it were described in the 2007 report. The places and timing of the deployment were designed to allow comparison between open zones and closed green zones (Marine National Park). Sites were chosen across the CapReef area with locations from inshore to the Keppel Islands. page 9

10 Pairs of open and green zone sites were chosen to be: Relatively close together; Similar in depth; Similar substrate type; and Likely to be inhabited by similar fish species. The BRUV equipment was deployed for one hour (three or four sets) at the green and open site consecutively. The site (green or open) of first deployment was chosen randomly by the flip of a coin. Sites chosen (figure 1) were: Pelican Island and Split Rock; Eastern North Keppel Island and Pumpkin Island; Barren Island and Egg Rock (2 occasions one set of deep and one of shallow sites); Miall and Middle Islands (2 occasions); 2 sites near Halfway Island (2 occasions); Cape Capricorn; and Shoalwater Bay. Depths ranged from 8-30m and substrates examined were coral, gorgonian coral (sea whip and sea fan) and rocky reef. Figure 1: Locations where BRUV video obtained at Keppel Bay sites Recorded digital video images were later viewed on a television monitor. Two variables were determined for each deployment (set): Abundance and types of fish observed to feed on the bait; and Abundance and types of fish apparently attracted to the feeding event but not feeding. The number of sets where each species was observed was also recorded. page 10

11 4. Results Comparison of Open and Green Zones Overall 308 fish from 45 species were recorded from open zones and 263 fish from 42 species in green zones. Of the 17 species recorded in both the open and green zones 211 fish were observed in open zones; and 196 in green zones. The split of the numbers of these species is given in figure 2. Number of fish FISH OBSERVED IN OPEN AND GREEN ZONES open green Starry Triggerfish Red Emperor Trevally Angelfish Remora Collar Seabream Monocle Bream Hussar Venus Tuskfish Saddletail Snapper Coral Trout Goldspotted Rockcod Grass Emperor Longfin Rockcod Painted Sweetlips Stripey Snapper Figure 2: Comparison of the number of fish observed in open and green zones Of the 17 species, 6 were observed more often in the open zones, 11 were observed more often in green zones. Another way of comparing the species is by comparing the number of sets each species is observed. This comparison is shown in figure 3. This shows that 9 species were observed in more sets in open zones while 8 were observed in more sets in green zones. page 11

12 % OF SETS OBSERVED % sets open %sets green Hussar Stripey Snapper Painted Sweetlips Grass Emperor Venus Tuskfish Longfin Rockcod Goldspotted Rockcod Coral Trout Trevally Collar Seabream Crimson Snapper Saddletail Snapper Remora Red Emperor Starry Triggerfish Angelfish Monocle Bream Figure 3: Comparison of the proportion of sets where fish were observed in open and green sites Four of the fish species were observed to feed more often in open zones, 13 in green zones. 42% of fish fed at the baits in open zones and 55% fed in green zones. This is shown in figure PERCENTAGE OF FISH FEEDING Open Green % of fish feeding All species Painted Sweetlips Trevally Remora Longfin Rockcod Coral Trout Goldspotted Rockcod Saddletail Snapper Crimson Snapper Stripey Snapper Venus Tuskfish Grass Emperor Monocle Bream Collar Seabream Angelfish Starry Triggerfish Hussar Red Emperor Figure 4: Comparison of the proportion of each species observed to feed in open and green sites page 12

13 Comparison of catch to BRUV observations The percentage of sets of the BRUV in open and green locations where species were observed was compared with the percentage of trips that caught the species. For the open zone data, four species were observed more frequently in the catch records and 13 were observed more frequently in the open location BRUV sets (figure 5). Only one of the species was recorded more frequently in the catch data than in the BRUV data from the green locations (figure 6) CATCH VS OPEN SETS %trips catching % sets open Longfin Rockcod Stripey Snapper Grass Emperor Goldspotted Rockcod Coral Trout Venus Tuskfish Hussar Red Emperor Saddletail Snapper Painted Sweetlips Trevally Collar Seabream Starry Triggerfish Remora Monocle Bream Angelfish % of fish Figure 5: Comparison of the proportion of trips where each species was reported in the catch and the proportion of sets where the species was seen in open zoned sites CATCH VS GREEN SETS %trips catching %sets green % of fish Longfin Rockcod Stripey Snapper Grass Emperor Goldspotted Rockcod Coral Trout Venus Tuskfish Hussar Red Emperor Saddletail Snapper Painted Sweetlips Trevally Collar Seabream Starry Triggerfish Remora Monocle Bream Angelfish Figure 6: Comparison of the proportion of trips where each species was reported in the catch and the proportion of sets where the species was seen in green zoned sites page 13

14 Species %kept Coral Trout 80.5 Grass Emperor 73.5 Venus Tuskfish 72.9 Hussar 48.0 Stripey Snapper 45.6 Saddletail Snapper 44.5 Painted Sweetlips 40.1 Collar Seabream 26.4 Goldspotted Rockcod 22.5 Red Emperor 14.5 Monocle Bream 4.3 Starry Triggerfish 3.1 Longfin Rockcod 0.6 Angelfish 0.0 Remora 0.0 Table 2: Percentage of species caught that are kept Species Were the % Sets in open zones > % of trips catching species? Coral Trout Grass Emperor Venus Tuskfish Hussar Stripey Snapper Saddletail Snapper Painted Sweetlips Collar Seabream Goldspotted Rockcod Red Emperor Starry Triggerfish Longfin Rockcod Angelfish Remora Were the % Sets in Green zones> % of trips catching species? Table 3: Percentage of BRUV sets in open and green zones greater than percentage of trips catching species page 14

15 5. Discussion Comparing open and green zones A common perception is that more fish are present within green zones than in open zones. The results presented here suggest that this may only be true for some locations and species. Approximately equal numbers of individual fish were recorded in closed and open zones in total, but this was variable with location and species. Location To make definitive statements about abundance of fish at individual sites will require more information from more visits, variation between visits was too great to reliably conclude which sites had more fish. However, in general, the sets at Miall Island showed more fish than those at the Middle Island sites. Similarly there were more fish recorded at the open Halfway Island site than at the green site. The opposite was true for the Split Rock/Pelican island sites and for the Barren Island/Egg Rock sites. Here there were more fish observed in the green sites. Reasons for this deserve greater research. Species Figure 2 shows that some species were more often recorded outside of green zones, in particular Monocle Seabream, Collar Seabream, Remora, Angelfish, Starry Triggerfish, Trevally and Red Emperor. Stripey Snapper, Coral Trout, Painted Sweetlips, Crimson Snapper, Longfin Rockcod, Grass Emperor, Goldspotted Rockcod, Venus Tuskfish and Hussar were seen in greater numbers within green zones. It is noteworthy that this split is closely related to the percentage of fish retained in the catch (Table 1). The fish most likely to be retained (for example Coral Trout, Grass Emperor and Venus Tuskfish) were more commonly observed in green zones than in open zones. Conversely fish seldom retained were more common in the open zones (eg Monocle Bream, Starry Triggerfish, Angelfish and Remora). The two species that don t fit this pattern are Trevally and Longfin Rockcod. Longfin Rockcod were more common in green zones despite being seldom retained. Trevally were more common in open zones but this is largely the result of one school of fish that approached the BRUV bait in one set. This deserves more research and a longer period of structured BRUV monitoring should provide further clarity on this issue. There was also a difference in the proportion of sets where fish were observed between open and green zones (figure 3). Several more species were more common outside of the green zones using this measure. Probably the best way to interpret this is that when a fish species was observed in a set in a green zone there was a good chance that several would be seen. That is for several species they were seen in more sets outside of the green but in smaller numbers. For example although Saddletail Snapper were seen in more sets outside of the green zones, they were in much larger numbers when seen in the sets in the green zones. page 15

16 Percentage of fish feeding The results show a similar trend to those of the first report in that a greater proportion of fish (56%) were observed to feed on baits in green zones than in open zones. Of the 17 species, 13 fed more frequently in the green zones. Only Trevally, Remora, Painted Sweetlips and Longfin Rockcod fed more frequently in open areas. A closer examination suggests that there is probably little difference in the feeding response of Red Emperor, Hussar, Starry Triggerfish, Angelfish or Longfin Rockcod. Differences in these could be explained by natural variation. Those that most obviously fed more often in green zones were Goldspotted Rockcod, Coral Trout, Saddletail Snapper, Stripey Snapper, Venus Tuskfish, Grass Emperor, Monocle Bream and Collar Seabream. Similar to the trends noted for the species most often observed in green zones, this includes the species most often retained (perhaps the most desirable food species such as Coral Trout, Grass Emperor and Venus Tuskfish). This suggests that the most desirable species are both more common in the green zones and more likely to feed on the baits. There are two reasons that could explain why this may be occurring. Either: fish learn to avoid fishing gear in the open zones and so become more cautious in open zones; or the more desirable fish that do feed on baits are removed perhaps leaving only more naturally cautious individuals that do not readily feed on baits and less desirable species that are released if caught. At present there is insufficient information to clarify this issue however continued sampling could provide some insights. During late 2007 an intensive tagging program involving the capture, tag and release of fish in green zones occurred. It might be expected that if learning to avoid fishing gear is involved, then this project may have influenced the proportion of fish feeding. If a change in the proportion of fish feeding occurs following this program it may indicate that fish learn to avoid fishing lines rather than being removed by fishing. Further structured BRUV monitoring may provide a valuable insight very relevant to management. For example if the results do indicate that some fish are more susceptible to capture, they may be rapidly removed after a green zone is opened to fishing. Comparing catch with BRUV observations The results from 2007/08 once again show no evidence of any popular species disappearing from open or green zones. As explained in the previous report, if fish are observed more frequently in the BRUV sets than they are found in catches it may indicate that fish are more common than catches indicate. In this report two measures are available for comparison with catches: BRUV observations from open sites and green sites. Table 3 and figure 5 shows that 10 of the 14 species available for comparison were observed more frequently in the BRUV, suggesting they may be more common than the catches suggest. Four species (Grass Emperor, Hussar, Stripey Snapper and Goldspotted Rockcod) were recorded in proportionally more trips than sets. Very similar results were found for the BRUV results for the Capricorn Bunker Group reported previously. This may suggest that these page 16

17 species are actively selected by line fishing. Alternatively it may be that the sites monitored did not have as many of these species as the locations used by fishers. Only one species (Trevally) occurred in proportionally more trips than sets from green zones (table 3 and figure 6) and if Trevally had been observed in more than one set in the green zones, then this result would also have changed. This reinforces that the green zones probably contain greater numbers of fish for most species. Figure 7: Trevally observed at Cape Capricorn page 17

18 5. References Platten J and Sawynok W (2007): Is what is there what you catch?: CapReef report STCR available at page 18