1. SPECIES DETAILS. Common Name or Names by Which the Species is Known [EPBC Regulation (b)]:

Transcription

1 Nomination to list the Rexea solandri, Gemfish (Eastern population) as Endangered under the Environment Protection and Biodiversity Conservation Act, SPECIES DETAILS Scientific Name of the species [EPBC Regulation (a)]: Rexea solandri Common Name or Names by Which the Species is Known [EPBC Regulation (b)]: Gemfish (eastern gemfish); Hake; King couta; kingfish; silver kingfish; southern kingfish; Is the species conventially accepted? [EPBC Regulation (c)]: Yes Category for which the species is nominated [EPBC Regulation (d)]: Endangered Rexea solandri, Gemfish (Eastern Population) 1. Scientific name, common name (where appropriate), major taxon group Rexea solandri, Gemfish (eastern gemfish); Hake; King couta; kingfish; silver kingfish; southern kingfish, family Gempylidae 2. National Context Gemfish live in relatively deep water ( m) on the upper continental slope off southern Australia and New Zealand. Gemfish are a large, predatory species, which grow to about 1.2 m in length and a weight of about 12 kg. Gemfish grow quickly, reaching a weight of 1 kg after 3 years and about 4 kg at 6 years of age. They mature at 4-6 years of age (60-70 cm in length), and the majority of fish in the breeding population range from 4 to about 8 years of age. The oldest gemfish aged to date was 17 years, however few fish survive beyond 12 years of age. Four separate populations of gemfish are recognised. Two populations occur in Australian waters, an eastern stock ranging from Tasmania to northern NSW (which is the subject of this nomination), and a western stock in the Great Australian Bight and WA waters. There are also 2 populations in New Zealand waters - a northern stock which occurs off the north-east coast of NZ and a southern stock which occurs off the western and southern coasts of the south island. Fish from each stock of gemfish spawn in a short, well defined season each year, and the four stocks are considered to be distinct breeding populations. Colgan and Paxton (1997) demonstrated that the eastern Australian stock and the southern/western Australian stock (the Western Stock) are genetically different, with virtually no gene flow or mixing between the two stocks. For fisheries management purposes, these eastern and western 1

2 populations can be considered to be separate breeding populations (Pogonoski et al 2001). Gemfish belonging to the eastern Australian stock undertake a pre-spawning migration along the upper continental slope off NSW at a depth of about 400 m. The migration commences in waters off eastern Bass Strait in early June and finishes off the NSW mid north coast in August, when spawning occurs. Prior to spawning the mature fish aggregate into schools near the seabed, and the available information indicates that at this time gemfish are very vulnerable to capture using demersal trawl nets and droplines. Each mature female gemfish is capable of producing between 0.5 and 6 million eggs in a spawning season. Little is known of the breeding biology of gemfish, or of the environmental factors influencing spawning success and larval survival. Despite their high reproductive capability, three of the four stocks of gemfish (the Eastern Australian stock and both New Zealand stocks) appear to have suffered major declines due to their failure to produce sufficient numbers of young fish (Annala et al, 2002). 3. Justification for this nomination. Criterion 1 - Decline in numbers TSSC: It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a severe reduction in numbers IUCN: A population reduction in the form of either: A. Reduction in population size based on any of the following: 1. An observed, estimated, inferred or suspected reduction greater than or equal to 70% over the last 10 years or three generations, whichever is the longer, where the causes of the reduction are clearly reversible AND understood AND ceased, based on (and specifying) any of the following: a) Direct observation b) An index of abundance appropriate for the taxon c) A decline in area of occupancy, extent of occurrence and/or quality of habitat d) Actual or potential levels of exploitation e) The effects of introduced taxa, hybridisation, pathogens, pollutants, competitors or parasites. 3. A population size reduction of greater than or equal to 50%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer (up to a maximum of 100 years), based on (and specifying) any of (a) to (e) under A1. This proposal will demonstrate that the eastern gemfish clearly meets both the EPBC and the IUCN criteria for listing as an endangered species, as the estimated reduction in eastern gemfish biomass over the last 21 years (approximately three generations of gemfish) exceeds endangered criterion requirements. 2

3 Years of targeted fishing of eastern gemfish have resulted in a significant reduction in the eastern stock. Estimates of the biomass of mature eastern gemfish prior to exploitation, range between 10 and 20 thousand tonnes (Allen and Rowling, 1998). Despite a zero catch quota being in effect since 1993, a 1997 assessment suggested that the spawning biomass was less than 40% of the 1979 level (Caton and McLoughlin 2000). By 1999, estimates of mature biomass in the middle of the 1999 fishing season ranged between 700 and 2600 tonnes or 5% to 16% of the unexploited equilibrium level (Anon., 1999). All scenarios indicate that the biomass of mature eastern gemfish is still declining, as trawlers continue to catch large quantities of juvenile fish as bycatch, before they are able to mature and contribute to the spawning population (Rowling and Makin, 2001). This view is reinforced by the actions of the Australian Fisheries Management Authority (AFMA) Board which recently wrote to SETMAC expressing concern about reports of trawlers targeting the gemfish pre- spawning aggregations in recent years, and requesting advice about how to minimise this practice (Rowling pers comm). Considering that the natural population of eastern gemfish should be (and has been) measured in the thousands of tonnes, and that the population is now too small to allow predictions about the population to be made with any confidence, this strongly implies that the eastern gemfish is at an extremely low and unpredictable level and one which requires significant action to engender recovery. *** The accurate assessment of the size and status of a fish stock is a difficult task, and relies on a large amount of consistent data collected over an extended period. Eastern gemfish presented a difficult assessment problem, being a deepwater migratory species, which had only recently been subject to fishing. The initial assessments (developed by Dr. K. R. Allen using a population modelling technique known as Cohort Analysis) indicated a possible decline in the biomass of mature gemfish during the early 1980's, and a reduction in the number of young fish entering the population after about 1984 (Allen 1989). Allen estimated from the cohort analysis that by 1986 the exploitable biomass of gemfish available to the winter fishery had declined to 40-50% of the unexploited level, and the biomass of mature females was estimated to be 33-57% of the unexploited level (Allen, 1989). The mid season biomass estimates for the mid 1980s were about 4500 to 5000t, which are very low when compared with the catches taken from the winter stock through that period of around 3000 t per season (Allen, 1989). Eastern gemfish are particularly vulnerable to over fishing as the majority of the catch is taken during their northward migration to the spawning grounds. During this migration, the fish form a narrow band, the so-called gemfish run, which is easily targeted. Targeted fishing for eastern gemfish commenced in about 1970, when trawlers began fishing new grounds along the continental slope. Very large catches of gemfish were taken during the short winter season as the aggregations migrated to their spawning grounds. Catches for single trawl shots ranged up to 30 tonnes, and shots of 10 to 15 tonnes were quite common in the peak of the season. Landings of eastern gemfish increased rapidly, peaking at more than 5000 tonnes in For most of the 1980's more than 3000 tonnes were landed during each winter season. The top catching vessels caught in excess of 300 tonnes per boat in their best seasons, and the average catch rate for all vessels in these early years was around 3.5 tonnes of gemfish per day (Rowling and Makin, 2001). Fishers generally saw these high catch rates as indicative of high fish abundance rather than of high vulnerability to fishing. Trawlers also took large catches of other species (redfish, 3

4 mirror dory, ocean perch and ling) on the same grounds as gemfish during the winter season. Smaller boats using droplines to target blue-eye also caught gemfish on grounds that were not subject to trawling. In the late 1980's, techniques to more effectively target gemfish with droplines were developed. More recently, some recreational and charter boat fishers have also targeted gemfish on certain grounds (Steffe et al., 1996.). During the 1980's average trawl catch rates declined markedly, and the size of gemfish in the winter catch also declined. These changes, which are not unexpected in a newly developed fishery, indicated a measurable impact of fishing on the stock. Rowling (1987) detailed the changes in the stock and suggested controls be put in place to prevent further increases in the gemfish catch. The fishing industry was highly critical of the initial assessment of the status of the gemfish stock, with fishers believing that fishing during the short winter season was not unduly impacting the species. In 1988, AFMA (the trawl fishery is managed under Commonwealth jurisdiction) implemented a catch quota of 3000 tonnes for gemfish. There was a considerable level of public protest by the fishing industry about the imposition of this quota. In 1989 the quota was allocated separately to individual operators, mainly on the basis of their catch history in the fishery. The total quota remained at 3000 tonnes in 1989, but as more detailed assessments of the status of the eastern gemfish stock became available in the early 1990's, the quota was reduced due to concern about a decline in the stock caused by falling numbers of juvenile fish entering the population. This and concern about a decline in the abundance of mature gemfish led to the implementation of a zero catch quota for the trawl fishery from 1993 to 1996 inclusive. However, small quantities (up to 200 kg) of gemfish taken incidentally while fishing for other species were still allowed to be landed. These fish were landed under the "trip limit" provisions, but gemfish in excess of the trip limit were discarded at sea. The virtual 'closure' of the gemfish fishery resulted in further protests by trawl fishers, which culminated in a 1993 research program undertaken by a consulting scientist to test the validity of the data used in the gemfish stock assessment (Prince and Wright, 1994). The results from this research supported the conclusion of the stock assessment that there had been a period of very poor recruitment to the gemfish stock. The zero quota remained in place, and the Eastern Gemfish By-Catch Working Group was formed to update the stock assessment for gemfish and advise on appropriate management of the fishery in a 'by-catch' situation. The catch of eastern gemfish taken by the winter trawl fishery can be used to broadly indicate trends in the mature population size, even under a zero targeted TAC. This is because a reasonable amount of trawling has occurred each season on the gemfish spawning run and in the gemfish depth range, irrespective of whether the fishing was targeted at gemfish or not. Monitoring of gemfish landings from 1993 to 1995 suggested improved recruitment from year classes spawned in 1990 and 1991 (even though the catch quota was zero, several hundred tonnes of gemfish were landed under the trip-limit provisions in each of these years). It was evident that significant numbers of maturing fish would enter the breeding population in However, as fishers were not permitted to target gemfish, commercial 4

5 catch rate information was not available to estimate gemfish abundance. Surveys were therefore conducted using chartered commercial trawlers to collect this information (Prince, 1996). Prior to the trawl survey in the 1996 winter season, the Eastern Gemfish Assessment Group (EGAG) was formed. EGAG's initial tasks were to design an appropriate trawl survey for the 1996 winter season, and to develop a computer model of the eastern gemfish stock which would use all the information available for the fishery, and would allow forward projections of abundance so that different management options could be considered. The stock assessment produced by EGAG following the 1996 season (Anon., 1997a) Indicated a significant improvement in the abundance of mature gemfish as the 1990 and 1991 cohorts began reaching maturity, and led to the re-opening of the fishery in 1997, when a Total Allowable Catch (TAC) of 1000t was set for the trawl fishery. It is significant that in the 1997 season when the fishery was opened, a highly targeted trawl fishery only caught approximately 350 tonnes of eastern gemfish. Acceptance of suggestions that bad weather or oceanographic factors led to this poor catch ignores the probability that the biomass of newly recruited fish was in fact much lower than had been estimated by the population models. If this was the case, then the by-catch of approximately 450 tonnes in 1996 and the targeted catch of 350 tonnes in 1997 may have removed a large proportion of the incoming cohort before the fish reached full recruitment at 7 years of age. (Such pressure on this cohort would have been exacerbated by the dropline fishery which also took approximately 300 tonnes of gemfish from the stock between 1995 and 1997, a proportion of which would have been from the 1990 cohort) (Rowling and Makin, 2001). The absence of targeted trawl surveys in the winters of 1999 or 2000 means that a defensible index of current mature biomass has not been obtained since Even if results from a targeted survey were available, it is uncertain if the type of survey undertaken to date adequately indexes the population abundance of eastern gemfish at very low stock sizes. The highly aggregated nature of pre-spawning gemfish means that the daily catch rate is likely to remain relatively high until an aggregation can no longer be found. Between 1998 and 1999, observers employed on the Integrated Scientific Monitoring Program (ISMP) collected information which showed a significant decline in catch rate of gemfish in all areas, and especially off Tasmania, where large fish comprised the bulk of catches in 1998 (Knuckey and Sporcic, 1999; Knuckey, 2000). In 1998, discarded fish comprised 9-11% of the gemfish catch by weight, and size composition data indicated these fish comprised both 1 and 3 year old fish. In 1999, discards increased to 24%, which was largely comprised of 1 year old fish. This data is consistent with a decline in the relative abundance of large gemfish, and an increase in the discard rate (due to discarding of small unmarketable fish) in trawl catches since 1998 (Rowling and Makin, 2001).. The conclusions above are supported by the results from the ISMP observers working aboard trawlers in the Commonwealth managed South East Fishery. The following figure shows the size composition of trawl catches of eastern gemfish measured during The bulk of fish caught by the trawl fishery were less than 50 cm LCF (3 years of age). Significant numbers of 1-year old fish (20-30 cm LCF) were discarded. 5

6 Eastern Gemfish Measured by ISMP Retained Discarded Number LCF cm (ISMP Unpublished data) The on-board observer data is reinforced by size composition data for landed catches of eastern gemfish for both winter trawl and dropline catches from 1996 to 2000 which suggest that the relative abundance of mature gemfish has significantly declined in 1999 and 2000 (Rowling and Makin 2001). Figures 6.2 and 6.3 from Rowling and Makin 2001 for trawl and dropline catches respectively (reproduced below) strongly suggest that the relative abundance of mature gemfish has significantly declined during 1999 and The most abundant size classes of eastern gemfish present in trawl catches during the main part of the winter season in 2000 were fish smaller than 45cm LCF (2 year old fish), the majority of which are immature and not capable of spawning effectively (Rowling and Makin, 2001). 11 % Freqency N = N = N = N = N = LCF cm 6

7 Figure 6.2 Size composition of TRAWL catches of eastern gemfish marketed in Sydney during June and July for the years 1996 to % Freqency N = N = N = N = N = LCF cm Figure 6.3 Size composition of DROPLINE catches of eastern gemfish marketed in Sydney during May, June and July for the years 1996 to

8 The implications of such a low spawning stock for future levels of recruitment are not known, but the potential failure of spawning, resulting in a completely missing year class, cannot be ruled out. The very poor year classes from 1987 to 1989 were produced by a spawning biomass many times greater than is likely to have occurred in The current understanding about trends in the eastern gemfish stock is summarised in the following figures. The results presented are from one of twenty model scenarios examined by EGAG in their 1999 assessment. All the scenarios depict the same overall trends in the stock from 1970 to 1999, but the actual values estimated for population quantities vary from scenario to scenario, depending on the assumptions and data used in each scenario. Estimates of the weight (biomass) of mature eastern gemfish prior to exploitation range between 10 and 20 thousand tonnes, while estimates of the mature biomass in the middle of the 1999 fishing season range between 700 and 2600 tonnes (Anon 1999). All scenarios indicate that the biomass of mature eastern gemfish is currently declining, and is expected to be much lower in the 2000 winter season (due to the poor age classes currently entering the mature population). Trends in the stock size after 2000 will depend entirely on the strength of newly maturing year classes, and as is explained below it is likely that the biomass of mature fish will continue to decline in the foreseeable future. The scenario chosen for presentation in Figures 1 and 2 (Scenario 10 in the 1999 EGAG Stock Assessment) is considered to show an 'average' picture of the likely trends in the eastern gemfish stock from 1970 to It is not one of the more optimistic scenarios which estimate 1999 biomass to be greater than 2000 tonnes. Alternatively, if catch rate (kilograms of gemfish per hour trawled) is a poor index of the abundance of mature gemfish at low population levels due to their aggregating behaviour, then current biomass may well be less than the value shown in Figure 1. Figure 1. Eastern Gemfish- Mature Biomass 1970 to 1999 Tonnes PRE-SEASON BIOMASS SPAW NING BIOM ASS 2000 TARGET BIOM ASS (NSW Fisheries. 1999) Year Figure 1 shows the trend in mature biomass of eastern gemfish estimated for scenario 10 of the EGAG 1999 assessment. As the majority of the catch is taken from the aggregations prior to spawning, two values are given for the mature biomass for each year. The thin line 8

9 ("pre-season biomass") shows the biomass estimated by the model at the start of the winter season, and the thick line ("spawning biomass") shows the biomass at the end of the winter season, which better reflects the actual spawning biomass in any year. The darker shading between these two lines represents the catch taken in each winter season. The dramatic decline in the 'spawning biomass' between 1979 and 1983 is readily apparent. It is also clear that the fishery took a relatively high proportion of the available (pre-season) biomass in the seasons from 1983 to Although there was a small improvement in the mature biomass in 1996 and 1997, this was not sustained and the stock is again declining. There is no doubt that the stock is now well below the 'target biomass', the minimum level considered by fishery managers to allow sustainable fishing of the stock. Figure 2 shows the estimates from the population model of the relative numbers of fish in year classes spawned from 1970 to The dotted line indicates the 'normal' level of year class strength (for eastern gemfish a normal year class is about 3 million fish at 3 years of age, which equates to about 3000 tonnes of biomass). Year class strengths were close to this level, or better, for nearly all years prior to However in the years since 1984 there has been an extended period of very poor year classes, with only the 1990 and 1991 year classes providing any significant recruitment. The estimates for the 1996 and 1997 year classes remain very uncertain at this time, and it should not be assumed these age classes are as strong as indicated in Figure 2. Figure 2. Eastern Gemfish - Year Class Strength 1970 to 1997 Note: Strength of 1996 and 1997 Year Classes Still Uncertain * Relative Strength * * (NSW Fisheries. 1999) Year The recruitment of so many poor year classes has resulted in large changes in the age structure of the breeding population. Fish from the last relatively abundant year classes (1990 and 1991) will be 9 and 10 years of age in the 2000 winter season. At these ages the number of fish in these year classes will be very much reduced by the effects of fishing and natural mortality. All other fish in the breeding population in 2000 will be from the poor 9

10 year classes spawned from 1992 to 1995, with the exception of the possible recruitment of improved numbers of 4 year old fish belonging to the 1996 year class. (However, it is known that only a small proportion of fish of age 4 are mature and become involved in the breeding aggregations). In 2001, NSW fisheries officers continued monitoring the size and numbers of gemfish landed (see figures below). There is little doubt that the reduction in the trip limit for gemfish significantly reduced targeted fishing for gemfish by NSW commercial line fishers after May However, monitoring by NSW Fisheries during 2001 of the size and numbers of gemfish landed by dropliners indicate that the majority of these fish were between 60 and 75 cm in length, mostly coming from the 1996 cohort (5 year olds). These data indicate that gemfish older than about 6 years (ie. from the 1990 and 1991 cohorts) appear to provide only a minor contribution to the spawning population in 2001 (Rowling 2001 unpublished). Furthermore, SEF trawlers continue to catch large numbers of juvenile gemfish (less than 3 years old), which is inconsistent with management aimed at promoting the recovery of the eastern stock of gemfish. NSW (all fisheries) t t t t (data extracted in April 2002 may be incomplete) C wealth (SEF) TAC Catch t 190 t t 130 t t 75 t t 79 t t n/a (Rowling pers comm.) The NSW data for 2001 indicate that although the 1996 cohort is indeed stronger than those which preceded it, as was expected from previous analyses, it is far smaller than the 1990 and 1991 cohorts. Unfortunately, the trawl fishery continues to cause significant mortality of all age classes, and the apparently poor catch rates of eastern gemfish during the 2001 winter season (whether from targeted fishing or as incidental catch) suggest that the biomass of mature fish remains dangerously low (Rowling 2001 unpublished). As mentioned in section 2, the two populations in New Zealand have also declined dramatically. Landings from the Southern Stock (southern and west coast, South Island) have declined from 6,900t in to 134t in as the TAC was reduced from >3000t to 600t over this period. There is evidence of very weak year classes entering this stock in the 1990s (Annala et al, 2002). Landings from the Northern Stock (East and west coasts of the North Island) have declined from 2300t in to 665t in The TAC has been reduced from 2350t to 980t over this period. Standardised CPUE indices have shown a decline of almost 90% in the fisheries on this stock. The base case model results suggest that the stock is about 16% of virgin biomass. Recent year class strengths appear very poor (Annala et al, 2002). 10

11 It is time to put in place management arrangements that protect spawning aggregations of eastern gemfish from the effects of fishing, so that fishing does not contribute to the further decline of the population. It is no longer appropriate to simply 'minimise the by-catch' of eastern gemfish. Recent history has shown that no such action will be taken if the species is not classified as endangered under the EPBC. Criterion 2 - Geographic distribution TSSC: Its geographic distribution is precarious for the survival of the species and is restricted. IUCN: B. Geographic range in the form of either B1(extent of occurrence) OR B2 (area of occupancy) OR both: 1. Extent of occurrence estimated to be less than 5000 sq km, and estimates indicating at least two of a-c: a. Severely fragmented or known to exist at no more than five locations. b. Continuing decline, inferred, observed or projected, in any of the following: Extent of occurrence Area of occupancy Area, extent and/or quality of habitat Number of locations or subpopulations Number of mature individuals. c. Extreme fluctuation in any of the following: Extent of occurrence Area of occupancy Number of locations or subpopulations Number of mature individuals. 2. Area of occupancy estimated to be less than 500 sq km, and estimates indicating any two of a-c as listed above. It is extremely difficult in the case of a migratory fish species to meet the IUCN spatial criteria. However, it can be argued under the EPBC criteria that the gemfish practice of congregating during spawning for the so-called gemfish run creates a geographic distribution that is very precarious for the survival of the species, and is restricted for the spawning period. Furthermore, given the recent collapse in numbers of gemfish caught as bycatch during the gemfish run, it can justifiably be argued that within the IUCN criteria, a continuing decline in extent of occurrence, area of occupancy and number of mature individuals have all been clearly documented. Targeting the spawning run has been a very effective means of rapidly reducing the number of breeding adults and hence overall recruitment to the population. It is now well established that the spawning stock of eastern gemfish suffered a significant collapse during the early 1990s, due to the poor recruitment of cohorts spawned during the late 11

12 1980s. Recent data show that for the eight spawning seasons from 1987 to 1994, only the 1990 and 1991 seasons resulted in a reasonable level of recruitment to the mature population (Rowling, 1998b). The spawning stock in recent years has become progressively more reliant on fish from these two cohorts, which must have been significantly reduced in abundance over the last few years due to the combined effects of fishing and natural mortality. The indications are that the spawning population will decline to a historically low level, as there is no evidence of any cohorts of reasonable strength about to recruit to the mature population (Rowling, 1998b). *** Gemfish live in relatively deep water ( m) on the upper continental slope off southern Australia and New Zealand. Four separate stocks of gemfish are recognised within this range. Two stocks occur in Australian waters, an eastern stock ranging from Tasmania to northern NSW (which is the subject of this nomination), and a western stock in the Great Australian Bight and WA waters. There are also 2 stocks in New Zealand waters - a northern stock which occurs off the north-east coast of NZ and a southern stock which occurs off the western and southern coasts of the south island. Fish from each stock of gemfish spawn in a short, well defined season each year, and the four stocks are considered to be distinct breeding populations. Colgan and Paxton (1997) demonstrated that the eastern Australian stock and the southern/western Australian stock (the Western Stock) are genetically different, with very little gene flow or mixing between the two stocks. For fisheries management purposes, these eastern and western populations can be considered to be separate breeding populations (Pogonoski et al 2001). Eastern gemfish are particularly vulnerable to over fishing as the majority of the catch is taken during their northward migration to the spawning grounds. During this migration, the fish form a narrow band, the so-called gemfish run, which is easily targeted. In the late 1970s, and throughout the 1980s, gemfish comprised a very significant proportion of demersal trawl catches off NSW. The bulk of the annual catch (3000 to 5000t) was taken during the winter months, as mature fish formed pre-spawning aggregations at depths of 350 to 450m, and while migrating northwards towards the spawning grounds. Additionally, juvenile and some adult gemfish were trawled year round on upper continental slope grounds off southern NSW and in eastern Bass Strait. In the late 1980s a dropline fishery also developed on a small number of suitable grounds along the NSW continental slope, and more recently gemfish have been targeted by recreational and charter boat fishers (Steffe et al, 1996) Monitoring of the size and age composition of gemfish landings in NSW commenced in the late 1970s, soon after the development of the fishery (Rowling, 1979). During the mid 1980s, analysis of data from monitoring of gemfish catches showed a decline in the average size of fish in the winter catches, and a reduction in the standardised catch rate for the trawl fishery. Following the release of a discussion paper (Rowling, 1987) a TAC of 3000t was introduced for gemfish for the 1988 winter fishery. The implementation of TAC management in the gemfish fishery coincided with a period where recruitment to the mature population was well below normal. As the magnitude of this failure in recruitment became apparent during the early 1990s, the TAC for eastern 12

13 gemfish was sequentially reduced. During this period there was considerable debate about the status of the resource, and the desirability and effectiveness of TAC management of the fishery (Anon., 1992; Rowling, 1991 and 1992). Following indications of four consecutive years of poor recruitment, the TAC for western gemfish was set to zero in However, debate about the status of the stock continued until the decline in recruitment was confirmed by the results of an industry based research project (Prince and Wright, 1994). The TAC for eastern gemfish remained at zero from 1993 to Throughout this period however, incidental catches of gemfish by both trawl and non-trawl fishers were marketed under trip limit provisions, and monitoring of these catches allowed continued assessment of the size and age structure of the gemfish population (Rowling, 1994b and 1995). The results of these assessments indicated that two slightly stronger year classes (spawned in 1990 and 1991) would enter the mature population as 5 and 6 year old fish in the 1996 winter season. To determine the likely improvement in the abundance of mature gemfish due to the recruitment of the 1990 and 1991 year classes, a research survey was conducted during the 1996 winter season (Prince, 1996) and monitoring of the commercial by-catch was continued. The design of the survey, and the incorporation of the results in a dynamic population model of the eastern gemfish stock, was undertaken by the newly formed eastern gemfish Assessment group (EGAG), which comprised industry, scientific, conservation and management representatives. The stock assessment produced by EGAG following the 1996 season (Anon., 1997a) indicated a significant improvement in the abundance of mature gemfish, and let to the re-opening of the fishery in 1997, when a TAC of 1000t was set for the trawl fishery. However, the 1997 fishery was singularly unsuccessful, with only 350t of gemfish being landed by the trawl sector. Inclusion of the results from monitoring of the 1997 commercial landings in EGAG s stock assessment resulted in a more pessimistic appraisal of the status of the eastern gemfish stock (Anon., 1997b). in 1998, management of the trawl fishery reverted to a zero targeted TAC for eastern gemfish, although a transferable bycatch TAC of 300t was allocated amongst individual trawl fishers in proportion to their eastern gemfish quota holdings, the aim being to minimise discarding of incidental catches. Similar arrangements were in place during subsequent years, except that the bycatch TAC was reduced to 250t in 1999, 200t in 2000 and 150t in Catches by non-trawl fishers have continued to be managed by way of trip limits, eg. 50kg per day for all methods during the 2000 winter season. There is now little doubt that the eastern gemfish stock has been very significantly reduced by a prolonged failure in recruitment and continued fishing pressure. Although there was some improvement in the stock abundance due to stronger age classes spawned in 1990 and 1991, recent data indicate that the year classes spawned from 1992 to 1995 are all well below normal levels of abundance. The mature population of eastern gemfish has declined further as these poor age classes recruited to the adult stock in recent years. It is not possible to accurately forecast the implications for future levels of recruitment of this further decline in the abundance of mature gemfish, but the stock is now well below the level considered necessary for a viable population (Rowling and Makin, 2001). Criterion 3 - Population size and decline in numbers or distribution TSSC: The estimated total number of mature individuals is low; and, (a) evidence suggests that the number will continue to decline at a high rate, or 13

14 (b) the number is likely to continue to decline and its geographic distribution is precarious for its survival. IUCN: C. Population size estimated to number less than 2500 individuals and 1. An estimated continuing decline of at least 20% within 5 years or two generations whichever is longer (up to a maximum of 100 years in the future) This proposal demonstrates that the eastern gemfish clearly meets both the EPBC and the IUCN criteria for listing as an endangered species, as the estimated reduction in eastern gemfish biomass over the last 21 years (approximately three generations of gemfish) far exceeds 50%. While it is not possible with a migratory fish species to determine with great accuracy the exact number of mature individuals remaining in the population, it is clear that the number of mature gemfish is very low. Furthermore, it is not known what effect this situation of low numbers will have on the spawning behaviour of the surviving adults. It is possible that there may be a numerical threshold below which the spawning behaviour will not be triggered. If they do spawn, the probability of the remaining adults being caught as bycatch or by the remaining boats determined to continue targeting the gemfish run remains too high. Years of targeted fishing of eastern gemfish have resulted in a significant reduction in the eastern stock. Estimates of the biomass of mature eastern gemfish prior to exploitation, range between 10 and 20 thousand tonnes (Allen and Rowling, 1998). Despite a zero catch quota being in effect since 1993, a 1997 assessment suggested that the spawning biomass was less than 40% of the 1979 level (Caton and McLoughlin 2000). By 1999, estimates of mature biomass in the middle of the 1999 fishing season ranged between 700 and 2600 tonnes or 5% to 16% of the unexploited equilibrium level (Anon., 1999). All scenarios indicate that the biomass of mature eastern gemfish is still declining, as trawlers continue to catch large quantities of juvenile fish as bycatch, before they are able to mature and contribute to the spawning population (Rowling and Makin, 2001). This view is reinforced by the actions of the AFMA Board which recently wrote to SETMAC expressing concern about reports of trawlers targeting the gemfish pre- spawning aggregations in recent years, and requesting advice about how to minimise this practice (Rowling pers comm). Considering that the natural population of eastern gemfish should be (and has been) measured in the thousands of tonnes, and that the population is now too small to allow predictions about the population to be made with any confidence, this strongly implies that the eastern gemfish is at an extremely low and unpredictable level and one which requires significant action to engender recovery. The accurate assessment of the size and status of a fish stock is a difficult task, and relies on a large amount of consistent data collected over an extended period. Eastern gemfish presented a difficult assessment problem, being a deepwater migratory species, which had only recently been subject to fishing. The initial assessments (developed by Dr. K. R. Allen using a population modelling technique known as Cohort Analysis) indicated a possible decline in the biomass of mature gemfish during the early 1980's, and a reduction in the number of young fish entering the population after about 1984 (Allen 1989). 14

15 Allen estimated from the cohort analysis that by 1986 the exploitable biomass of gemfish available to the winter fishery had declined to 40-50% of the unexploited level, and the biomass of mature females was estimated to be 33-57% of the unexploited level (Allen, 1989). The mid season biomass estimates for the mid 1980s were about 4500 to 5000t, which are very low when compared with the catches taken from the winter stock through that period of around 3000 t per season (Allen, 1989). Eastern gemfish are particularly vulnerable to over fishing as the majority of the catch is taken during their northward migration to the spawning grounds. During this migration, the fish form a narrow band, the so-called gemfish run, which is easily targeted. Targeted fishing for eastern gemfish commenced in about 1970, when trawlers began fishing new grounds along the continental slope. Very large catches of gemfish were taken during the short winter season as the aggregations migrated to their spawning grounds. Catches for single trawl shots ranged up to 30 tonnes, and shots of 10 to 15 tonnes were quite common in the peak of the season. Landings of eastern gemfish increased rapidly, peaking at more than 5000 tonnes in For most of the 1980's more than 3000 tonnes were landed during each winter season. The top catching vessels caught in excess of 300 tonnes per boat in their best seasons, and the average catch rate for all vessels in these early years was around 3.5 tonnes of gemfish per day ((Rowling and Makin, 2001). Fishers generally saw these high catch rates as indicative of high fish abundance rather than of high vulnerability to fishing. Trawlers also took large catches of other species (redfish, mirror dory, ocean perch and ling) on the same grounds as gemfish during the winter season. Smaller boats using droplines to target blue-eye also caught gemfish on grounds that were not subject to trawling. In the late 1980's, techniques to more effectively target gemfish with droplines were developed. More recently, some recreational and charter boat fishers have also targeted gemfish on certain grounds (Steffe et al., 1996.). During the 1980's average trawl catch rates declined markedly, and the size of gemfish in the winter catch also declined. These changes, which are not unexpected in a newly developed fishery, indicated a measurable impact of fishing on the stock. Rowling (1987) detailed the changes in the stock and suggested controls be put in place to prevent further increases in the gemfish catch. The fishing industry was highly critical of the initial assessment of the status of the gemfish stock, with fishers believing that fishing during the short winter season was not unduly impacting the species. In 1988 the Australian Fisheries Management Authority (the trawl fishery is managed under Commonwealth jurisdiction) implemented a catch quota of 3000 tonnes for gemfish. There was a considerable level of public protest by the fishing industry about the imposition of this quota. In 1989 the quota was allocated separately to individual operators, mainly on the basis of their catch history in the fishery. The total quota remained at 3000 tonnes in 1989, but as more detailed assessments of the status of the eastern gemfish stock became available in the early 1990's, the quota was reduced due to concern about a decline in the stock caused by falling numbers of juvenile fish entering the population. This and concern about a decline in the abundance of mature gemfish led to the implementation of a zero catch quota for the trawl fishery from 1993 to 1996 inclusive. However, small quantities (up to 200 kg) of gemfish taken incidentally while fishing for 15

16 other species were still allowed to be landed. These fish were landed under the "trip limit" provisions, but gemfish in excess of the trip limit were discarded at sea. The virtual 'closure' of the gemfish fishery resulted in further protests by trawl fishers, which culminated in a 1993 research program undertaken by a consulting scientist to test the validity of the data used in the gemfish stock assessment (Prince and Wright, 1994). The results from this research supported the conclusion of the stock assessment that there had been a period of very poor recruitment to the gemfish stock. The zero quota remained in place, and the eastern gemfish By-Catch Working Group was formed to update the stock assessment for gemfish and advise on appropriate management of the fishery in a 'by-catch' situation. The catch of eastern gemfish taken by the winter trawl fishery can be used to broadly indicate trends in the mature population size, even under a zero targeted TAC. This is because a reasonable amount of trawling has occurred each season on the gemfish spawning run and in the gemfish depth range, irrespective of whether the fishing was targeted at gemfish or not. Monitoring of gemfish landings from 1993 to 1995 suggested improved recruitment from year classes spawned in 1990 and 1991 (even though the catch quota was zero, several hundred tonnes of gemfish were landed under the trip-limit provisions in each of these years). It was evident that significant numbers of maturing fish would enter the breeding population in However, as fishers were not permitted to target gemfish, commercial catch rate information was not available to estimate gemfish abundance. Surveys were therefore conducted using chartered commercial trawlers to collect this information (Prince, 1996). Prior to the trawl survey in the 1996 winter season, the eastern gemfish Assessment Group (EGAG) was formed. EGAG's initial tasks were to design an appropriate trawl survey for the 1996 winter season, and to develop a computer model of the eastern gemfish stock which would use all the information available for the fishery, and would allow forward projections of abundance so that different management options could be considered. The stock assessment produced by EGAG following the 1996 season (Anon., 1997a) Indicated a significant improvement in the abundance of mature gemfish as the 1990 and 1991 cohorts began reaching maturity, and led to the re-opening of the fishery in 1997, when a Total Allowable Catch (TAC) of 1000t was set for the trawl fishery. It is significant that in the 1997 season when the fishery was opened, a highly targeted trawl fishery only caught approximately 350 tonnes of eastern gemfish. Acceptance of suggestions that bad weather or oceanographic factors led to this poor catch ignores the probability that the biomass of newly recruited fish was in fact much lower than had been estimated by the population models. If this was the case, then the by-catch of approximately 450 tonnes in 1996 and the targeted catch of 350 tonnes in 1997 may have removed a large proportion of the incoming cohort before the fish reached full recruitment at 7 years of age. (Such pressure on this cohort would have been exacerbated by the dropline fishery which also took approximately 300 tonnes of gemfish from the stock between 1995 and 1997, a proportion of which would have been from the 1990 cohort) (Rowling and Makin, 2001). 16

17 The absence of targeted trawl surveys in the winters of 1999 or 2000 means that a defensible index of current mature biomass has not been obtained since Even if results from a targeted survey were available, it is uncertain if the type of survey undertaken to date adequately indexes the population abundance of eastern gemfish at very low stock sizes. The highly aggregated nature of pre-spawning gemfish means that the daily catch rate is likely to remain relatively high until an aggregation can no longer be found. Between 1998 and 1999, observers employed on the Integrated Scientific Monitoring Program collected information which showed a significant decline in catch rate of gemfish in all areas, and especially off Tasmania, where large fish comprised the bulk of catches in 1998 (Knuckey and Sporcic, 1999; Knuckey, 2000). In 1998, discarded fish comprised 9-11% of the gemfish catch by weight, and size composition data indicated these fish comprised both 1 and 3 year old fish. In 1999, discards increased to 24%, which was largely comprised of 1 year old fish. This data is consistent with a decline in the relative abundance of large gemfish, and an increase in the discard rate (due to discarding of small unmarketable fish) in trawl catches since 1998 (Rowling and Makin, 2001).. The conclusions above are supported by the results from the ISMP observers working aboard trawlers in the Commonwealth managed South East Fishery. The following figure shows the size composition of trawl catches of eastern gemfish measured during The bulk of fish caught by the trawl fishery were less than 50 cm LCF (3 years of age). Significant numbers of 1-year old fish (20-30 cm LCF) were discarded. Eastern Gemfish Measured by ISMP Retained Discarded Number LCF cm (SMP Unpublished data) The on-board observer data is reinforced by size composition data for landed catches of eastern gemfish for both winter trawl and dropline catches from 1996 to 2000 which 17

18 suggest that the relative abundance of mature gemfish has significantly declined in 1999 and Figures 6.2 and 6.3 from Rowling and Makin, 2001 for trawl and dropline catches respectively (reproduced below) strongly suggest that the relative abundance of mature gemfish has significantly declined during 1999 and The most abundant size classes of eastern gemfish present in trawl catches during the main part of the winter season in 2000 were fish smaller than 45cm LCF (2 year old fish), the majority of which are immature and not capable of spawning effectively (Rowling and Makin, 2001). % Freqency LCF cm 96 N = N = N = N = N = 2668 Figure 6.2 Size composition of TRAWL catches of eastern gemfish marketed in Sydney during June and July for the years 1996 to % Freqency N = N = N = N = N = LCF cm Figure 6.3 Size composition of DROPLINE catches of eastern gemfish marketed in Sydney during May, June and July for the years 1996 to

19 The implications of such a low spawning stock for future levels of recruitment are not known, but the potential failure of spawning, resulting in a completely missing year class, cannot be ruled out. The very poor year classes from 1987 to 1989 were produced by a spawning biomass many times greater than is likely to have occurred in The current understanding about trends in the eastern gemfish stock is summarised in the following figures. The results presented are from one of twenty model scenarios examined by EGAG in their 1999 assessment. All the scenarios depict the same overall trends in the stock from 1970 to 1999, but the actual values estimated for population quantities vary from scenario to scenario, depending on the assumptions and data used in each scenario. Estimates of the weight (biomass) of mature eastern gemfish prior to exploitation range between 10 and 20 thousand tonnes, while estimates of the mature biomass in the middle of the 1999 fishing season range between 700 and 2600 tonnes (Anon., 1999). All scenarios indicate that the biomass of mature eastern gemfish is currently declining, and is expected to be much lower in the 2000 winter season (due to the poor age classes currently entering the mature population). Trends in the stock size after 2000 will depend entirely on the strength of newly maturing year classes, and as is explained below it is likely that the biomass of mature fish will continue to decline in the foreseeable future. The scenario chosen for presentation in Figures 1 and 2 (Scenario 10 in the 1999 EGAG Stock Assessment) is considered to show an 'average' picture of the likely trends in the eastern gemfish stock from 1970 to It is not one of the more optimistic scenarios which estimate 1999 biomass to be greater than 2000 tonnes. Alternatively, if catch rate (kilograms of gemfish per hour trawled) is a poor index of the abundance of mature gemfish at low population levels due to their aggregating behaviour, then current biomass may well be less than the value shown in Figure 1. Figure 1. Eastern Gemfish- Mature Biomass 1970 to 1999 Tonnes PRE-SEASON BIOMASS SPAW NING BIOM ASS TARGET BIOM ASS (NSW Fisheries. 1999) Year Figure 1 shows the trend in mature biomass of eastern gemfish estimated for scenario 10 of the EGAG 1999 assessment. As the majority of the catch is taken from the aggregations prior to spawning, two values are given for the mature biomass for each year. The thin line ("pre-season biomass") shows the biomass estimated by the model at the start of the winter season, and the thick line ("spawning biomass") shows the biomass at the end of the winter season, which better reflects the actual spawning biomass in any year. The darker shading between these two lines represents the catch taken in each winter season. 19