Exotic fish impact

Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.

Attribute data

TitleExotic fish impact

CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment

CreatorGIS Unit, Information and Land Services Division, Department of Primary Industries and Water (DPIW)

DescriptionAn index which rates the relative ‘nativeness’ of freshwater fish assemblages, which reflects the presence and relative biomass of exotic fish assemblages.

Input data

1. CFEV Rivers spatial data
2. CFEV Waterbodies spatial data (valid and invalid)
3. Exotic fish biomass data, Freshwater Systems
4. Historical trout stocking data, Inland Fisheries Service (IFS)
5. Hydro infrastructure and discharge data (location), Hydro Tasmania
6. Land Information System Tasmania (LIST) 1: 250 000 Geology data, DPIW
7. LIST Waterfall data, DPIW
8. Regional Forest Agreement (RFA) fish database (updated for the CFEV Project), DPIW

Lineage

The exotic fish data was developed for rivers and waterbodies using two types of information:

1. the distribution of exotic fish (probabilities of occurrence assigned to river and waterbody spatial units)
2. the relative biomass of exotic fish (based on the relationships shown in Figure 1).

Exotic fish distribution

Data on exotic freshwater fish distribution was prepared using:

1. records of known locations with exotic fish prepared during the RFA (P. Davies & L. Cook, Freshwater Systems, unpublished data) and updated for the CFEV Project:
1. Salmo trutta (brown trout)
2. Oncorhynchus mykiss (rainbow trout)
3. Salvelinus fontinalis (brook trout)
4. Salmo salar (Atlantic salmon)
5. Perca fluviatilis (redfin perch)
6. Tinca tinca (tench)
7. Carassius auratus (goldfish)
8. Gambusia holbrookii (mosquito fish)
9. Cyprinus carpio (European carp)
2. records and input from a number of freshwater fish experts.

The following rules for constructing the exotic fish distribution data provide no distinction between the various exotic fish species, noting that brown trout are by far the dominant species in terms of distribution and biomass. The rules were based on characteristics associated with the distribution of salmonid fish and assume that all other exotic fish fall within that statewide distribution. No account is taken of the elimination of fish species by pollutants (e.g. King River). The exotic fish distribution data (present, low probability or absent) was assigned to river sections and waterbodies.

1. Exotic fish are absent in (the following list may have some duplication):
1. the catchments of Port Davey and Bathurst Harbour
2. King Island (with the exception of those river sections upstream and downstream of those waterbodies listed as stocked in Table 1)
3. all river sections (and their associated waterbodies) upstream of the most downstream 100 m reach with a slope of 75% or greater
4. all river sections (and their associated waterbodies) upstream of all mapped waterfall features (whether they are named or not) (LIST waterfall data)
5. the river sections/waterbodies listed in Table 2.
6. other unnamed lakes on the Mersey map sheet as per map in (Sloane and French 1991). Note: All waters upstream of the waters listed in this metadata are also trout free – whether connected by the drainage disconnected from the drainage.
7. Those waterbodies listed in Table 3.
2. Exotic fish have a low probability of occurrence (and/or low abundance) in:
1. river sections with fine substrates (sands, silts) or catchments dominated by such reaches (examples include the catchments of Crayfish Creek, Boobyalla River, Tomahawk River, Botanic Gardens Creek at Strahan). This occurs when slope is <10% and geology along the river section and/or in the immediate upstream catchment is predominantly (>50% by total channel length) one of the following types: undifferentiated Quaternary sediments (1:250 000 geology map Rcode 8493 ‘Q’), undifferentiated Cainozoic sediments (1:250 000 geology map Rcode 8494 ‘TQ’) or sand, gravel and mud of alluvial, lacustrine and littoral origin (1:250 000 geology map Rcode 8499 ‘Qh’)?
2. in all catchments draining to the sea westwards from South-east Cape to Port Davey and from Port Davey to Cape Sorell
3. Exotic fish are believed to be present, i.e. have a high probability of occurrence, in all other river sections where the above rules do not apply, except for selected known locations where they have been stocked upstream of natural barriers. These include:
1. all lakes in the central highlands to the east of and including Great Lake
2. Swan River upstream of Hardings Falls
3. Clarence Lagoon
4. all Hydro lakes, storages and infrastructure, and river sections upstream for which the above rules do not apply
5. artificial barriers such as all water storage lakes infrastructure and river sections upstream for which the above rules do not apply (e.g. Rileys Creek, Pet and Guide, etc.) as identified in Table 1.

Table 1. Waterbodies known to have sustained trout populations established by stocking (IFS trout stocking data).

WB_ID	Waterbody name	Unique Feature Identifier (UFI) (LIST) for those waterbodies not assessed by CFEV (e.g. farm dams, etc.)
	Pet	hyd004046581
	Guide	hyd004046579
	Kara	hyd004048543
140	Talbots Lagoon
	Rileys Creek	hyd004916793
	Companion Reservoir	hyd004046580
	Mikany	hyd004676549
144	Lake Gairdner
166	Lake Mackenzie
	Rushy	hyd004129147
131	Curries River Reservoir
	Cascade	hyd004214444
	Frome	hyd004214443
	Monarch	hyd004639583
	Near Lake Leake	hyd004923553
1200	Craigbourne Dam
1339	Big Lagoon
1258	Lake Skinner
	Edgar Levee Pond	hyd005060875
	Mossy Marsh	hyd005004585
	Wentworth dam	hyd005009957
	Dunnys dam	hyd005009985
	Weasel Plains dam	hyd005287901
	West Queen Dam 2	hyd004219156
	West Queen Dam 1	hyd004219172
	West Queen Dam 3	hyd004224338
504	Lake Augusta
902	Little Pine Lagoon
638	Lake Selina
1074	Clarence Lagoon
1336	Hartz Lake
1327	Lake Perry
1328	Lake Osborne
1258	Lake Skinner
1230	Lake Belton
1228	Lake Belcher
1222	Lake Seal
1229	Lake Dobson
1224	Lake Fenton
162	Dove Lake
729	Junction Lakes
650	Lake Meston
152	Lake Youl
622	Lake Myrtle
557	Lake Bill
148	Lake Lea
995	Lake Beatrice
1096	Lake Bantick
619	Lake Botsford
3	Cask Lake (King Island)
201	Lake Chambers
629	Lake Chipman
527	Lake Dudley
1101	Lake Garcia
197	Lake Johnny
836	Langdon Lagoon (Brook Trout)
1098	Lake Ashwood
1104	Little Bellinger
562	Little Blue Lake
1	Lake Wickham (King Island)
723	Lake Mikany
7	Pennys Lagoon (King Island)
610	Plimsoll (Brook Trout)
617	Rocky Lagoon
628	Second Lagoon
1258	Lake Skinner
554	Tin Hut Lake
1105	Big Jim Lake
1130	Highland Waters
1125	Lake Samuel
1135	Tooms Lake
939	Lake Leake
1215	Lake Webster
1217	Twisted Tarn
1333	Lake Esperance
1219	Lake Hayes
1221	Lake Nicholls
728	Lake Rolleston
	Waratah Reservoir	hyd005249767
	Bischoff Reservoir	hyd005249765 hyd005152411 hyd004739827
	Waratah Ponds	hyd005152405 hyd005152406 hyd005152407

Table 2. Trout-free river sections and waterbodies.

WB_ID	Site name	Map name	D/S limit of trout-free river section Easting	D/S limit of trout-free river section Northing
	Unnamed tributary of Olive Lagoon	Olive	446700	5354875
	Johnsons Lagoon and headwaters	Olive	447650	5350775
	Unnamed stream, Skullbone Plains	Ina	449100	5346525
	Dyes Marsh and headwaters	Bronte Ina	448400	5337500
	Tibbs Plain	Bronte	440225	5336775
	Unnamed lagoon, Wentworth Hills	D’Arcys	443525	5327400
	Swan River tributary	Henry St John	591400	5367900
	Blue Tier Creek	Colonels	562125	5337175
	Parramores Creek	Leake	563800	5342100
	Tater Garden Creek – east	Colonels	565100	5334050
	Tater Garden Creek – west	Colonels	565100	5334050
	Snaky Creek	Colonels	565100	5334050
	Tullochgorum Creek	Fingal	580500	5383100
	St Pauls River	St John Fingal	589450	5377500
	Dukes River	St John Fingal	589450	5377500
	Lost Falls Creek	Leake	573500	5344800
	Cygnet River	Snow	573075	5355200
	Coghlans Creek	Ross Leake	559500	5344100
	Green Tier Creek	Royalty Tooms	561700	5317500
	Brodribb Creek	Leake	568350	5342800
	Rocka Rivulet	Royalty Tooms	563600	5318800
835	Lake Athena
819	Lake Pallas
770	Orion Lakes
631	Chalice Lake
773	Lake Merope
786	Lake Eros
765	Lake Artemis
817	Lake Payanna
652	Cloister Lagoon
763	Ling Roth Lakes
896	Lake Jackie
	lake on tributary of Lake Jackie to the north
455	Lake Howe
517	New Years Lake
437	Lake Sidon
408	Lake Thor
371	George Howes Lake
463	Lake Salome
452	Lake Tyre
510	Hunters lake
805	Lake Norman

Table 3. Trout-free waters within the Western Lakes – Central Plateau WHA area. Note: All waters upstream of these waters are also trout free – whether connected by the drainage or free standing.

WB_ID	Name
1024	Lake Sappho
993	Rim Lake
892	Lake Riengeena
512	Lake Louisa
520	Lake Adelaide

Relative biomass

Native fish diversity is known to decline with distance from the coast in Tasmanian streams (Davies 1989) and is associated with a dominance of brown trout in mid and upper catchment reaches. Analysis of quantitative electro fishing survey data (including data derived by Davies (1989), and other unpublished data) from 84 Tasmanian river sites confirmed that the proportion of native fish biomass in riverine fish assemblages decreases with distance from the sea (the tidal limit) (Figure 1).

(a)

(b)

Figure 1. Proportion of fish biomass as native species declines with distance from the sea (data re-analysed from Davies (1989) and P. Davies, Freshwater Systems, unpublished data) (a) scatter plot showing the input data and the relationship between the two variables (line represents a spline fit) (b) box plot showing the median values when data was grouped into four distance classes, based on expert analysis of the data.

The exotic fish distribution was combined with biomass proportion information using a final set of rules for assigning an exotic fish index to river sections and waterbodies (given below). The exotic fish condition index spans from 0 (high probability of exotic fish; proportion of fish biomass as native fish = approx. zero) through 0.04, 0.32, 0.65 (high probability of exotic fish, proportion of fish biomass as native fish = 0.04, 0.32 or 0.65, respectively) and 0.8 (low probability of exotic fish) to 1 (exotic fish absent).

The numbers used here are the medians of the proportion of fish assemblage biomass that is made up of native species (PBNAT) as shown in the box plot in Figure 1b.

Data limitations

The exotic fish impact data is highly derived and inherits all the data limitations of the derivation processes and input data.

Date createdSeptember 2004

Scale and coverage1:25 000; Statewide

References

Davies, P.E. (1989). Relationships between habitat characteristics and population abundance for brown trout, Salmo trutta L. and blackfish, Gadopsis marmoratus Rich. in Tasmanian streams. Australian Journal of Marine and Freshwater Research 40: 341-359.

Sloane, R.D. and French, G.C. (1991). Trout Fishery Management Plan Western Lakes - Central Plateau Tasmanian World Heritage Area. Unpublished report to the Parks and Wildlife Service, Tasmania.

Column headingRS_EXOTICF, WB_EXOTICF

Type of dataCategorical

Number of classes6

Assigning values to ecosystem spatial units

River sections (RS_EXOTICF) and waterbodies (WB_EXOTICF)

An index, based on the proportion of the fish assemblage biomass that consists of native fish species was assigned to river sections and waterbodies using the following rules. Probabilities of the presence of exotic fish described in rules above. The distance the spatial units were from the sea (upstream point of the estuary) was calculated using the drainage network numbering system and cumulative river section lengths.

1. If exotic fish probability = absent, assign score = 1 else
2. If exotic fish probability = low, assign score = 0.8 else
3. If exotic fish probability = present, then:
1. if distance of river section or waterbody is 0-20 km from sea, then assign score = 0.65 else
2. if distance of river section or waterbody is 21-40 km from sea, then assign score = 0.32 else
3. if distance of river section or waterbody is 41-60 km from sea, then assign score = 0.04 else
4. if distance of river section or waterbody is >60 km from sea, then assign score = 0

CFEV assessment framework hierarchy

1. Rivers>Condition assessment>Naturalness score (RS_NSCORE)>Biological condition (RS_BIOL)
2. Waterbodies>Condition assessment>Naturalness score (WB_NSCORE)>Native fish condition (WB_FISHCON)