Acknowledgements V Summary VI 1 General introduction 1 1 Barred Galaxias 1




НазваниеAcknowledgements V Summary VI 1 General introduction 1 1 Barred Galaxias 1
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3.3 Results

3.3.1 Translocation


A total of 92 Barred Galaxias were collected from a combined distance of 374 m from the two reaches in Kalatha Creek (Table 4) with adult fish (> 55 mm in LCF) accounting for 91% of all fish collected. The smallest fish recorded was 40.0 mm in length and weighed 0.5 g. Fifty adults were selected for translocation to Shaw Creek and the remainder were returned to their point of capture (Table 4). The average length of adult Barred Galaxias translocated to Shaw Creek was 78.1 mm, ranging from 55–106 mm. One hundred and twenty larval Barred Galaxias, averaging 14.0 mm in length (range: 11–17 mm), were released at Shaw Creek.

Seventy two Barred Galaxias were collected from a combined distance of 570 m from two reaches in Luke Creek (Table 4) with all classified as adult fish (> 55 mm in LCF). The smallest fish recorded was 58 mm in length and weighed 1.5 g. Forty adults were selected for translocation to Taponga River (Table 4) and the remainder were returned to their point of capture. The average length of the translocated fish was 86.3 mm, ranging from 58.0–114.0 mm. One hundred and twenty larval Barred Galaxias, averaging 13.8 mm in length (range: 11–18 mm), were released at Taponga River.

All fish selected for translocation were in good health before and after transportation, and following 10–45 minutes of acclimatisation. During acclimatisation water quality of fish holding tanks had equilibrated to conditions measured in the respective translocation sites and fish were behaving normally and actively swimming. Adult fish were released across a distance of 175 m and 130 m at Shaw Creek and Taponga River respectively and larval fish over a 100 m reach in each recipient stream (Figure 15).

3.3.2 Post-monitoring


During the three-month post-monitoring event (Table 2), 125 Barred Galaxias were collected each from the source reaches within Kalatha and Luke creeks (Table 5). At Kalatha Creek, fish averaged 69.6 mm in length (range 35.0–114.0 mm) and 70 % were adults. At Luke Creek, fish averaged 76.4 mm in length (range 36.0–119.0 mm) and 80 % were adults. Fish densities (fish/100 m stream length) were higher than when fish were collected for translocation and size and weight ranges did not indicate a negative impact from fish removal as they had not reduced (Table 4, Table 5).

Table 4. Number (n) and size (average length/weight (range) mm/g) of Barred Galaxias collected from Kalatha and Luke Creeks and those translocated to Shaw Creek and Taponga River. Distance (m) indicates the total reach length from which fish were collected from within source creeks and the reach length that adult fish were released into at translocation streams.


Waterbody

Distance
surveyed
(m)


n

Fish/100 m stream length

Proportion of adults – > 55 mm (%)

Average length (range) (mm)

Average weight (range) (g)

Source

Kalatha Creek

374

92

25

91

74.6

(40.0–106.0)

4.1

(0.5–12.2)

Luke Creek

570

72

13

100

86.1

(58.0–114.0)

6.1

(1.5–14.2)

Translocation

Shaw Creek

175

50

29

100

78.1

(55.0–106.0)

4.7

(1.0–12.2)

Taponga River

130

40

31

100

86.3

(58.0–114.0)

5.9

(1.5–14.2)



Table 5. Number (n) and size (average length/weight (range) mm/g) of Barred Galaxias collected at source and translocation creeks during three and six month post-monitoring events.

Water body

Distance surveyed (m)

n

Fish/100 m stream length

Proportion of adults – >55 mm (%)

Average length (range) (mm)

Average weight (range) (g)

3 month post-monitoring










Source



















Kalatha Creek

177

125

70

70

69.6

(35.0–114.0)

4.1

(0.3–15.8)

Luke Creek

257

125

49

80

76.4

(36.0–119.0)

4.8

(0.4–16.7)

Translocation
















Shaw Creek

475

13

3

100

84.5

(55.0–110.0)

8.1

(1.0–17.9)

Taponga River

530

14

3

100

96.4

(58.0–112.0)

10.6

(1.4–17.4)

6 month post-monitoring










Source



















Kalatha Creek

177

66

37

85

76.6

(41.0–106.0)

4.9

(1.5–14.3)

Luke Creek

300

61

20

84

79.1

(46.0–117.0)

5.1

(0.8–16.3)

Translocation
















Shaw Creek

475

6

1

100

82.0

(55.0–98.0)

7.6

(1.1–13.1)

Taponga River

530

6

1

100

85.6

(58.0–119.0)

7.0

(1.5–13.3)



Only adult Barred Galaxias were collected at the translocated sites during the three-month post-monitoring event (Table 5). Twenty six percent (n = 13) of fish translocated to Shaw Creek were recaptured, and 35 % (n = 14) were recaptured at Taponga River, representing individuals across the length range of fish translocated to each stream. Fish density in each system had declined by approximately 10 fold from 29–31 fish/100 m of stream length to a density of three. Fish recaptures demonstrate that a proportion of translocated Barred Galaxias survived at each site, however the decline in fish density may indicate mortality, fish moving from the site of release to occupy new habitat, or both. Inherent sampling inefficiencies may also account for a decrease in fish numbers, but sampling was undertaken in March when stream conditions were optimal for sampling (clear water and low water levels).

Fish were absent from the range expansion reach downstream of the adult release reach in both streams, though a 55 mm LCF individual and two individuals, 55 and 105 mm in length, were found in the upstream range expansion reaches in Shaw Creek and Taponga River respectively. These fish had migrated minimum distances upstream of 35 m and 88 m respectively, indicating that some fish had undertaken upstream movement and that each translocated population had expanded in range within its recipient stream.

No larval fish were detected, though this was not surprising given the difficulty in detecting small sized individuals and the amount of habitat into which they were released. If the larval fish survive and grow, this cohort should be able to be detected in subsequent sampling events as they increase in size, particularly during the 12 month post-monitoring event as they should be approximately 30–40 mm in length (T. Raadik, unpublished data).

During the six month post-monitoring event, 66 and 61 Barred Galaxias were collected from Kalatha and Luke creeks respectively (Table 5). At Kalatha Creek, fish averaged 76.6 mm in length (range 41.0–106.0 mm) and 80 % were adults. At Luke Creek, fish averaged 79.1 mm in length (range 46.0–117.0 mm) and 84 % were adults. Fish densities (fish/100 m stream length) were slightly higher than when fish were collected for translocation and size and weight ranges did not indicate a negative impact from fish removal as they had not reduced (Table 4, Table 5).

During the six-month post-monitoring event only adult Barred Galaxias were again collected at the translocated sites (Table 5). Twelve percent (n = 6) of adults translocated to Shaw Creek were recaptured and 15 % (n = 6) were recaptured at Taponga River, again representing individuals almost across the length range of fish translocated to each stream. This further demonstrates that a proportion of translocated Barred Galaxias had survived at each site. Fish density in each system had declined further, from three fish/100 m of stream length to a density of one/100 m. Fish recaptures demonstrate that a proportion of translocated Barred Galaxias survived at each site for six months post-release, however the further decline in fish density is considered related to potential mortality and fish movement, as discussed above, and to increased sampling inefficiency due to higher flows during the mid-June monitoring period. Consequently, the density of fish in the translocation reaches is considered to be higher than that recorded.

Barred Galaxias were again absent from the range expansion reaches downstream of the adult release reaches in both streams. Continued upstream movement of fish was demonstrated by the collection of five fish each in the upstream adult release reaches at Shaw Creek and Taponga River, and one fish each (55 mm LCF and 56 mm LCF) in the upstream larval release reach in each system. These two fish had migrated minimum distances upstream of 139 m and 214 m respectively in 6 months.

The gonad maturation stage of adult fish collected at source and translocated sites during the six month post-monitoring event varied between Stage 2 – Developing virgin and recovering spent to Stage 6 – Ripe (data not shown), with the majority of individuals at Stage 3 – developing or Stage 4 – maturing. Only a few individuals were at Stage 6 – ripe (Figure 17). This indicates that fish in source and translocation streams were undertaking reproductive development, which was typical for that time of year when compared with previous monitoring data for the species (T. Raadik, unpublished data). Importantly, reproductive development was occurring in translocated fish which may lead to some spawning at these new sites in the first year of establishment.

No fish collected during both post-monitoring events displayed signs of adverse physical condition (i.e. fin damage, lesions, starvation) and were therefore considered healthy.

Figure 17. Barred Galaxias collected during the six month post-monitoring event: (A) Gravid female from Shaw Creek; (B) Milt produced by a mature male from Kalatha Creek; (C) Smallest adult Barred Galaxias translocated at Shaw Creek (55 mm LCF). (Images: A– Michael Nicol, B– Renae Ayres,
C– Michael Nicol).

A


B

C

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