Boom and no bust for a teatfish in Torres Strait, Australia from combined forms of western and Indigenous management

Black teatfish (Holothuria whitmaei) is a high value sea cucumber that has been listed under the Convention on International Trade of Endangered Species (CITES) Appendix II. The Black teatfish fishery in Torres Strait, Australia, is fished solely by Indigenous Torres Strait Islanders. Black teatfish were closed to fishing in 2003, based on the results of stock surveys and concerns of overexploitation. A stock survey in 2009 found the Black teatfish population had recovered substantially but the fishery was again closed after trial openings exceeded catch limits. In line with a new harvest strategy adopted for the fishery in 2019, we conducted a stock survey in 2019–2020 that suggested the stock had recovered sufficiently to support a sustainable catch limit of 20 t. Empowering Indigenous Torres Strait Islanders to use Island custom alongside western management strategies, contributed to the success of a trial opening in 2021. The combination of a harvest strategy developed in consultation with traditional owners, a rigorous scientific survey and trial opening protocols informed by Island custom, supported the CITES positive Non‐Detriment Finding for the Torres Strait Bêche‐de‐mer Fishery. This is a significant example of the successful recovery and ongoing sustainable management of a depleted sea cucumber population.


| INTRODUCTION
Slow-moving marine invertebrates that are easy to catch, such as sea cucumber, abalone, scallop, and sea urchin, are vulnerable to overexploitation and often fishery managers are unable to recover depleted stocks (Conand, 2018;Hobday et al., 2001;Johnson et al., 2012;Stotz & Gonz alez, 1997).Sea cucumbers are particularly susceptible to overexploitation as they are easy to collect, inexpensive to process to bêche-de-mer (dried body wall), and are in high demand by luxury food markets in Asia.Catch trends for sea cucumber fisheries worldwide follow well documented boom and bust cycles due to low mobility of adults, density-independent reproduction, variable recruitment rates, and are compounded by socioeconomic factors (Anderson et al., 2011;Conand, 2006;Purcell et al., 2013;Uthicke et al., 2009;Wolfe & Byrne, 2022).
The high value Black teatfish (Holothuria whitmaei) is found in shallow tropical seas across the Indo-Pacific.In 2019, Black teatfish was listed under the Convention on International Trade of Endangered Species (CITES) Appendix II, due to falling status measures and to ensure that international trade does not threaten survival of the species (Pavitt et al., 2021).Future international trade is subject to binding trade measures that require export documentation, demonstrating legality and sustainability of the fishery commodities (CITES, 2019;Conand, 2018).
Torres Strait sea cucumber populations (located between mainland (Queensland) Australia and Papua New Guinea), have been fished for trade since around 1863 (Mullins, 1995).The sub-fishery for Black teatfish in Torres Strait resumed in the early 1990s after a decades' long dormancy, through renewed interest from fishers due to a growing export market (Conand, 2004).Black teatfish in Torres Strait are managed as part of a multi-species fishery known as the Torres Strait Bêche-de-mer Fishery (TSBDMF) (Plaganyi et al., 2020).The TSBDMF is wholly commercial and only fished by Indigenous Torres Strait Islanders.Any Indigenous Torres Strait Islander can hold a fishing license to fish any Torres Strait fishery.Fishers are required to land their catch at (licensed) catch landing points (fish receivers), who are required to complete catch records and forward these to a management agency.The fishery is managed by the Australian Commonwealth, through international management arrangements under the Protected Zone Joint Authority (PZJA) between Australia and Papua New Guinea (Butler et al., 2019).The TSBDMF has been managed based on information gathered by scientific surveys and incorporation of traditional and local Indigenous knowledge through regular working groups and resource assessment groups, that include representation of Indigenous Torres Strait Islander traditional owners, management agencies, and scientists.
In 2019, a Harvest Strategy was endorsed and implemented for commercial sea cucumber species in Torres Strait-the Torres Strait Bêche-de-mer Harvest Strategy (TSBDMHS) (AFMA, 2019;Plaganyi et al., 2020).The TSBDMHS is a protocol agreed on by all Indigenous Torres Strait Islander traditional owners, for monitoring, assessment, and management of the fishery into the future.It uses scientific data and acknowledges and incorporates traditional and local Indigenous knowledge, as well as customary and traditional laws for the individual nation groups of Torres Strait (Plaganyi et al., 2020).Nation groups also have the ability to implement additional management for fishery resources locally within communities through, for example, voluntary spatial closures.
Torres Strait Bêche-de-mer Fishery stock surveys were undertaken in 1995-1996, 2002, 2005, and 2009.Based on these surveys and reports of depletion by Torres Strait Islanders, the Black teatfish sub-fishery was closed to fishing in 2003 due to concerns of overexploitation (Skewes et al., 2004).The 2009 survey found that the Black teatfish population had recovered substantially but the fishery was again closed after two trial openings both exceeded catch limits.The new TSBDMHS prescribed that closed species could only be opened on a trial basis, if the results of a survey suggested the stock had recovered adequately (to around the Maximum Sustainable Yield Level).Black teatfish are additionally treated as a high-value target stock that requires focused data and assessment methods, to inform on the stock status and sustainable quotas.Given the length of time since the last survey in 2009 and additional certainty required by the Black teatfish CITES listing, there was a need for a new survey to inform on Black teatfish stock status.
Here we summarize findings of a 2019-2020 Torres Strait Black teatfish stock survey and infer stock status by comparison to previous surveys, as well as unfished stocks in other regions.We discuss how comanagement has enabled stock recovery and maintenance and is supporting ongoing sustainable management for this CITES-listed species.
This study showcases a success story for the recovery of an overexploited Black teatfish fishery.This was achieved through a combination of sustained scientific research effort and Indigenous Torres Strait Islander traditional owner buy-in, alongside community involvement in aspects of the science, western management, and use of traditional management.This is particularly significant for Indigenous peoples who are custodians for their sea country, allowing them to maintain their cultural way of life through the integration of western and Indigenous knowledge systems.

| Study site
The main fishing grounds of the Torres Strait Bêche-de-mer Fishery are located in a 16,844 km 2 area of East Torres Strait, northern Australia.The area accounts for approximately 64% of reef habitats in Torres Strait (Murphy, Skewes, Plag anyi, Edgar, & Salee, 2021).The first survey undertaken in 1995-1996 surveyed the whole of Torres Strait, subsequent surveys then focused on East Torres Strait, which is classified as all reefs to the East of the Warrior Reef complex (Figure 1).This was based on sea cucumber species distribution, with sandfish (Holothuria scabra) predominately found on Warrior Reef and Black teatfish (and other species) found on reefs to the East of Warrior Reef (Figure 1).
East Torres Strait is further divided into six fishing zones based on historical sea cucumber catch, holothurian abundance, and physiographic characteristics for habitats.These zones include: Barrier, Cumberland, Darnley, Don Cay, Great North East Channel, and Seven Reefs.For the 2019-2020 survey, a marine habitat map that delineated shallow reefs was superimposed on the fishing zones and used as the basis for site selection in the survey (Figure 1; Reference maps used for East Torres Strait were: AIMS-NESP reef map (Lawrey & Stewart, 2016), 1:100,000 Topographic map series [Royal Australian Survey Corps; Murphy, Skewes, Plag anyi, Edgar, & Salee, 2021;Taranto et al., 1997]).Reef habitat was further divided into four habitat strata: the reef top, the reef top buffer (a 200 m wide buffer around the inside of the shallow reef margin), the reef edge, and the deep reef (>20 m) stratum.

| Survey data collection
The 2019-2020 survey was conducted within the same timing of previous surveys to reduce differences in survey observer rates due to sea cucumber burrowing behavior, caused by seasonal and tidal factors.Two field surveys were conducted in November 2019 and January 2020, with 297 sites visited, across four habitat strata in the six fishing zones.Of the 297 sites surveyed, 161 were repeated from previous surveys (Table 1).The deep reef habitat stratum was sampled for the first time in 2019-2020.
Sites were located using a portable GPS and data were collected by two divers operating from a 5 m inflatable Naiad.Survey methods were similar to those undertaken for all previous surveys (Skewes et al., 1998;Skewes et al., 2004;Skewes et al., 2010).For the reef top and reef top buffer strata, a diver swam along a 40 m transect using a Chainman device (Leeworthy & Skewes, 2007) and recorded resource and habitat information 2 m either side of the transect line.Holothurians and other benthic fauna of commercial or ecological interest were counted and where possible, collected and returned to the dinghy with total length measured and weight recorded using a hand-held scale.For the reef edge strata, two divers swam adjacent transects perpendicular to the reef edge, from the reef crest to a depth of 20 m or a distance of 100 m, whichever came first.Divers counted and collected species of interest and recorded habitat information using the same protocol as the reef top and reef top buffer.The deep-water strata were surveyed for the first time in 2019-2020 using a modified drop camera for 10 min drifts, over transect lengths of 40 m to 675 m, ranging between 20 m to 50 m depths (see method paper; Murphy, Skewes, Edgar, Salee, & Plag anyi, 2021).

| Data analyses
Estimates of mean density (number per hectare) were derived using a stratified analysis of transect counts based on zones and strata.This takes into account the heterogeneity in the variance of observed counts and is representative of the physical size differences of the varying habitats in the surveys.For investigating trends in species density, we compared data from survey sites within fishing zones, based only on strata that were sampled in previous years.Four zones were consistently sampled in 1995-1996, 2002, 2009, and 2019-2020: Cumberland, Darnley, Don Cay, and Great North East Channel;and three strata: reef top, reef top buffer, and reef edge.
Estimates of standing stock were calculated as the product of the population estimate (density (count per ha)) by reef (strata) area and average weight from size frequency data collected during the survey.These data are suitable for calculating standing stock estimates for the surveyed areas, but not for direct comparison between years because they are specific to survey year and location.As the fishery catch in Torres Strait is recorded as (mostly) landed (gutted) weight (AFMA, 2019), we converted our standing stock estimate (whole live) to landed (gutted) weight for comparison with catch data using updated fishery conversion factors (Murphy, Skewes, & Plag anyi, 2021).The available stock above the fishery size limit (>250 mm total length) was also calculated.
We reported a conservative stock estimate (previously used in management considerations for this stock), being the 90th percentile of the bootstrapped mean estimate of the distribution (L90th) (this assumes that the real estimate would be 90% certain of being greater than this value).Bootstrap confidence intervals were derived via the mirrormatch bootstrapping technique (Sitter, 1992).Mirror-match bootstrapping extends standard resampling methodology to stratified, multistage sample designs by emulating the original within-stratum sampling procedure.Confidence intervals were set as the quantile corresponding to the desired percentile of the distribution.In our case, we were interested in the bottom 90th percentile.The use of an increasing number of runs was tested to ensure that bootstrap summary statistics converged satisfactorily, with results corresponding to using 1000 bootstrap runs.
All statistical analyses and modeling were performed in MS-Excel and in the software R (R Core & Team, 2022).

| Stock status
Stock status is typically assessed as the population density or biomass relative to its virgin (before fishing) density (biomass), which is related to the ecological system carrying capacity for that species.Current stock status was inferred by comparison of density estimates from the 2019-2020 survey with previous surveys in Torres Strait as well as to densities in other Black teatfish fisheries in Australia (Benzie & Uthicke, 2003;Knuckey & Koopman, 2016;Shiell & Knott, 2010;Uthicke & Benzie, 2001) and the South Pacific (Pakoa et al., 2014).
Density estimates for Black teatfish from other fisheries were identified from a review of current literature (we assessed studies based on species, habitat descriptions, and survey techniques).This allowed for comparison of densities for the TSBDMF against other Black teatfish fisheries in Australia located in similar habitats, as well as identification of natural (or unfished) densities.Density estimates for Black teatfish from Indo-Pacific nations were also used for comparison to Australian fisheries and we defined regional reference densities.
An important comparative study to Torres Strait, is the adjacent Great Barrier Reef (GBR; Queensland) Black teatfish fishery.In 1999, stock status was assessed using density estimates in the "main habitat" (described as the shallow  , 2003).
A further stock survey of the GBR fishery was carried out in 2015 (Knuckey & Koopman, 2016).It focused on the same area ("main habitat") as the 1999 survey, however delineated the survey habitat area as the 200 m reef edge buffer on the weather (South-East facing) side of reefs >1 km 2 (Knuckey & Koopman, 2016).The survey found Black teatfish mean densities of 13.5 (closed reefs) and 12.5 (open reefs) individuals per ha in exposed midshelf reefs and mean densities of 27.0 (closed reefs) and 23.6 (open reefs) individual per ha for outer barrier reefs, in the exposed reef buffer (200 m) habitat (Knuckey & Koopman, 2016).Based on the results of the 2015 survey, the fishery was subsequently opened in 2019.

| 2019-2020 survey
The 2019-2020 survey results for Black teatfish showed that the Barrier zone had the highest "whole of reef" (i.e., all strata) average density at 17.5 per ha, followed by the Don Cay zone at 14.6 per ha.Among the four habitat strata, densities were greatest for the reef top buffer (with the Barrier zone 19 per ha and Seven Reefs 9 per ha), followed by the reef edge, then the reef top strata.No Black teatfish were observed in the deep-water strata (Table 2).
The estimated standing stock (B) for Black teatfish was 1238 t and the bootstrapped lower 90th percentile of the stock estimate was 787 t (L90th).The available stock above the fishery size limit (operational stock) was 172.3 t.

| Comparison to previous Torres Strait surveys
The 2019-2020 standardized survey index of abundance was compared with previous surveys and confirmed that the Black teatfish stock has recovered from the earlier heavy depletion (noting that the first (1995)(1996) survey was undertaken after the fishery had been operating for several years).The recent survey in 2019-2020 found a similar density to the 2009 survey (with smaller associated standard deviation), suggesting Black teatfish in Torres Strait have remained at higher densities than during the earlier overfished period (Figure 2).
Survey length measurements for Black teatfish for 2019-2020 showed the widest range of any previous survey, including several of the largest animals recorded during surveys.Size distribution showed a bias toward smaller animals, which was expected as the stock is recovering (Figure 3).

| Comparison to other fisheries
Studies for the GBR indicated that densities in the GBR reef buffer zone of midshelf and outer barrier reefs, had a stock abundance range of 12.5-27 individuals per ha (Benzie & Uthicke, 2003;Knuckey & Koopman, 2016).This compares well with the density observed in the reef top buffer strata for the 2019-2020 survey of East Torres Strait, with densities of 21.3-26.8per ha for Black teatfish recorded in similar habitat.
T A B L E 2 Mean density (number per ha) for Black teatfish (Holothuria whitmaei) in each zone and stratum in 2019-2020.

Zone
Reef A review of survey data for Black teatfish throughout the Indo-Pacific concluded densities above 12.5 per ha represent a "natural" (unfished) density in "suitable habitat" (Kinch et al., 2008).Other estimates of unfished density at Ningaloo reef, Western Australia (WA) indicate 11.4-17.1 per ha in "habitats occupied by Black teatfish" and likely represent minimum natural population densities for Ningaloo reef, with this population not subjected to commercial fishing (Shiell & Knott, 2010).
There can be large variability in benthic communities and higher localized Black teatfish densities can occur.Guidance from the Secretariat Pacific Community provides "rule of thumb" regional reference densities of 50 individuals per ha for Black teatfishestimated from the upper 25% of densities across 91 sites assessed in 17 countries, over the period 2002-2012 (Pakoa et al., 2014).The highest site density observed during the 2019-2020 survey of East Torres Strait was 167 per ha and the mean of the upper 25% of densities in the reef top buffer strata for all reefs was 62.6 per ha and 82.3 per ha for the Don Cay and Barrier zones combined.
Overall, comparisons with regional density data from Australia and the Indo-Pacific, suggest that Black teatfish populations in East Torres Strait observed during the 2019-2020 survey, are at near natural densities (Figure 4).

| Black teatfish reopening process
Reopenings of Black teatfish to fishing in 2014 and 2015 followed rigorous decision making processes undertaken by fishery working groups, involving Indigenous Torres Strait Islander representatives, management, and scientists.Outcomes from science surveys and their interpretation based on comparison with other Black teatfish fisheries were considered and 15 t trial quotas set.Catch limits were exceeded both years due to poor (voluntary) catch reporting and pulses in fishing effort and the Black teatfish sub-fishery of the TSBDMF was subsequently closed.

| Trial Black teatfish reopening-2021
The trial reopening in 2021 differed from previous openings as it included the application of Harvest Strategy requirements, including compulsory catch reporting and an Indigenous Torres Strait Islander led industry workshop that agreed to implementing "Ailan Kastom" (Island custom) traditional management, alongside western management (AFMA, 2021).
To complement the survey, the operational stock biomass estimate for Torres Strait was used in conjunction with a Pella-Tomlinson biomass dynamics population model to recommend a 21 t catch limit (higher TAC's resulted in fishery decline) (Murphy, Skewes, Plag anyi, Edgar, & Salee, 2021).The 20 t reopening catch limit for Black teatfish was agreed to by all Indigenous Torres Strait Islander traditional owners (a one tonne buffer was desired by Black teatfish fishers to prevent over catch for the species; under the TSBDMHS if quota was exceeded the species would be closed to fishing and a scientific survey required to open).
In February 2021, a Bêche-de-mer industry led workshop for Black teatfish fishers from the Kemer Kemer Meriam and Kulkalgal Nations was held to discuss timing for the reopening (based on weather and to ensure that fishing did not overlap with the winter spawning period (Murphy et al., 2019)), catch reporting requirements, and traditional owner rights and cultural protocols (Ailan Kastom) for communities to self-manage fishery access in their sea country (AFMA, 2021).
In April 2021, a trial opening for the Black teatfish fishery was undertaken with real time catch reporting (catch receivers were required to send an image of completed catch records electronically to management, on the same day that catch was received).The ability for Ailan Kastom to limit effort and ensure stock sustainability, was clearly demonstrated when the fishery shut after 4 days with 17.4 t taken from a maximum limit of 20 t.Black teatfish fishers were highly organized among themselves, fishing reefs further out from home reefs the first day and working in closer the following days.On the final day, fishers returned early to land catch in anticipation of nearing quota, with potential for traditional management arrangements for future rotational access to the final catches (Table 3).

| DISCUSSION
The Torres Strait Black teatfish sub-fishery was closed in 2003 in response to concerns of overexploitation.A stock survey in 2009 found the population had recovered substantially, however failed openings in 2014 and 2015 exceeded catch limits, due to poor catch reporting and pulses in fishing effort.In line with a new Harvest Strategy (TSBDMHS) adopted for the fishery in November 2019 (Plaganyi et al., 2020), we conducted a stock survey in 2019-2020 to inform on whether another trial opening was possible.The 2019-2020 survey suggested that Black teatfish biomass could support a sustainable catch limit of 20 t and the fishery was able to carry out a successful trial opening in 2021.The ability for the fishery to adhere to new catch reporting requirements and limit effort to ensure sustainability, was clearly demonstrated when the catch limit was not exceeded and the opening of the fishery was deemed successful (and subsequently reopened in 2022 and 2023).This is one of the few examples documented worldwide, of the successful recovery of a depleted sea cucumber population and ongoing sustainability, using a mixed local and national management approach for the fishery.
Sea cucumber stock surveys undertaken in 1995-1996, 2002, 2005, 2009, and 2019-2020 provided essential information for assessing status with some degree of certainty.However, the initial surveys (1995)(1996) are not considered reliable due to high variability in Black teatfish density averages.This can be attributed to refining of survey methods and advancement of field technology (e.g., hand-held GPS units to locate sites).There are also a differing number of sites sampled between surveys (full scale vs. relative surveys undertaken), as well as nonspecific Black teatfish habitat surveyed because the TSBDMF is a multispecies fishery.The reliability of initial survey data for new fisheries starting out is not uncommon and introduces challenges for assessing the stock, often requiring science to play catch up later on (Exeter et al., 2021).
Fortunately, historical surveys in Torres Strait have been carried out using the same sample design and survey approach, therefore comparisons of density over time likely indicate actual population status (within the bounds of statistical confidence).The survey data allowed an assessment of the relative trends in the density of Black teatfish in East Torres Strait, with the survey conducted in 2019-2020 finding similar high densities to 2009, which are the highest densities for all surveys.The operational stock biomass (above fishery size limit) also showed an approximate three-fold increase from 52.9 t in 2009, to 172.3 t in 2019-2020 (Murphy, Skewes, Plag anyi, Edgar, & Salee, 2021;Skewes et al., 2010).Smaller sized Black teatfish were again recorded during the most recent survey (compared to the fishery size limit), however as the population is recovering this can be expected.Fishers however target Black teatfish specific habitat and therefore a higher number of larger sized animals are anticipated to be found.Overall, the data indicate a healthy stock, which is supported from comparison with other Black teatfish fisheries in Australia and the Indo-Pacific region.
The use of precautionary management has proven important for rebuilding Black teatfish stocks in Torres Strait.Increasing emphasis on the use of precaution in decision making for fisheries management is recognized as important for all stages of the management process for mitigating uncertainties (Ogawa & Reyes, 2021;Weeks & Berkeley, 2011).This is because a number of uncertainties remain related to the biology of Black teatfish and catch history in Torres Strait.Mortality for Black teatfish remains unknown, with the species believed to be long lived and having variable recruitment (Uthicke et al., 2004).The current density relative to virgin biomass (the population was already fished before the first stock survey in [1995][1996] is unknown and the reliability of catch data is variable, with voluntary (resulting in patchy) catch reporting prior to 2017.The TSBDMHS maps a pathway for these uncertainties, through ongoing improvements and refinements for resource assessments into the future, that are important for sustainability for the species (Plaganyi et al., 2020).
There is an increasing necessity for ongoing community empowerment, for the successful comanagement of Indigenous fisheries to achieve good stewardship.The understanding of and incorporation of Indigenous knowledge and traditions to fisheries management is essential for future sustainability of stocks through local community support and uptake of best practice (Clarke & Jupiter, 2010;Eckert et al., 2018).This is particularly important for the Indo-Pacific region where sea cucumber fishing is a primary source of income for many Island nations (Purcell et al., 2016).For example, in New Caledonia, recognizing local fisher organizations and territorial fishing rights, was identified as an important factor for increasing sea cucumber resources and catches (Leopold et al., 2013).In Manus (Papua New Guinea) marine protected areas for sea cucumbers were established in 2013 as part of the Mwanus Endras Tribal Network (MENAR), along with trained community monitors to survey areas (Hausheer, 2019).Furthermore, the Island nations of Palau, Pohnpei, and Yap in Micronesia (Indo-Pacific) banned the trade of sea cucumber at its financial peak through public demonstration and implementation of customary and statutory law, which is believed to have prevented fishery collapse (Ferguson et al., 2022).
Empowering Indigenous Torres Strait Islander traditional owners and communities to use Ailan Kastom alongside western management strategies, through good stewardship, is believed to have contributed to the success of the 2021 Black teatfish reopening, after previous failed fishing trials.This allowed an additive value of traditional management of fishing compliance and enforcement of the TAC, that western management was unable to implement.A further example of Ailan Kastom management and science integration is in place for the Prickly redfish (Thelenota ananas) sub-fishery in Torres Strait, which has seen increasing fishing pressure in recent years.During the development of the TSBDMHS, communities agreed between themselves to not fish during spawning periods for the species and there are also recognized nursery (juvenile) areas that are not fished (Plaganyi et al., 2020).Traditional owners also hold a strong sense of custodianship for their fisheries and typically recommend conservative fishing limits to ensure ongoing resource sustainability (Plaganyi et al., 2018;Plaganyi et al., 2020).
The recovery of Black teatfish is an important achievement for Indigenous Torres Strait Islanders, in order to fully utilize their resource.This is particularly significant in East Torres Strait where the high value Tropical Rock Lobster (Panulirus ornatus) fishery offers fewer opportunities due to unsuitable habitat and sea cucumber has the potential to provide moderate longterm income to local Indigenous Torres Strait Islander communities.Across Torres Strait, fishing (in general) remains the main source of income to communities and supports long standing traditional identity and cultural heritage for the region (Plaganyi et al., 2013).
There will be a continued requirement for close monitoring of Black teatfish in Torres Strait.As fisheryindependent data in the form of scientific surveys are costly and sporadic, fishery dependent data collected during future Black teatfish sub-fishery openings can be used to routinely inform the TSBDMHS.These data will include size frequency and weight measurements, which are important primary indicators for the Harvest Strategy.Commencing collection of time series data is important for understanding stock dynamics and how yields will change over time in response to changing size structure.Future planning will also include documenting effort for areas fished during openings, as well as fishers using GPS data loggers to capture catch-per-unit-effort data for the sub-fishery.
Reopening Black teatfish to fishing may bring renewed interest in the fishery.The open-ended nature of effort (any Indigenous Torres Strait Islander can apply for a license to fish the fishery) and the possibility of large pulses in fishing due to community interest and momentum from buyer interest, could contribute to the risk of localized overexploitation.Ongoing careful management that includes Ailan Kastom is essential for stock sustainability and continued good stewardship for the resource.The implementation of the Torres Strait Bêche-de-mer Harvest Strategy, is helping provide the necessary protection to sea cucumber populations through the key control of setting a cap on total catch limits for species.Other important controls allow for spreading of fishing effort, limiting effort pulses, mitigating localized depletion, collection of valuable fishery and fishery-independent data, and carrying out catch monitoring and resource assessments as required (Plaganyi et al., 2020).This is particularly important for meeting listing requirements of Teatfish species on CITES Appendix II, with outcomes of the 2019-2020 sea cucumber stock survey supporting the current CITES positive Non-Detriment Finding for the Torres Strait Bêche-de-mer Fishery.

POSITION STATEMENT
The authors recognise Ailan Kastom (Island custom) as the cultural laws for groups of Torres Strait Islands that form individual nations.Ailan Kastom is used in the form of traditional management to supplement western fishery management, through the implementation of Malo ra GELAR (Malo's Law) of Kemer Kemer Meriam Nation, Saabi law of Maluilgal Nation, Saabi law of Gudumalulgal Nation, Kulkalgal Nation and Saabi law of Kaurareg Nation.These cultural laws govern 'who, where and how' to fish and are based on complex relationships for Indigenous Torres Strait Islander kinship, individual Island community arrangements and individual nation agreements, which evolve over time.The paper is a collaboration between non-Indigenous researchers addressing a research priority as determined by fishery consultative fora, where Indigenous representatives for Torres Strait Island communities and nations have a voice.The authors follow protocols prescribed in the Torres Strait Indigenous Engagement Strategy for engaging in science research, that requires undertaking Island community consultation.The research did not require human or animal ethics approval.The authors are fortunate to be regularly hosted on Torres Strait land and sea country and were particularly interested to show how closing the gap between western and Indigenous management systems, facilitated an important local fishery to recover from overfishing and be maintained sustainably.The authors participated in resource assessment and fishery management meetings; and were invited to Indigenous led workshops, to codesign research, present the outputs of fishery assessments, and collaboratively formulate management strategies with Indigenous representatives.The authors recognise that maintaining and strengthening Indigenous knowledge systems alongside western science and management, is essential to building the Torres Strait nations capacity for managing their enduring connection to land and sea resources, for future generations.

ACKNOWLEDGMENTS
This project was funded by the Torres Strait Regional Authority (TSRA), the Australian Fisheries Management Authority (AFMA), and the Commonwealth Scientific and Industrial Research Organisation (CSIRO).Thank you to S. Edgar and K. Salee for valuable assistance during field surveys and to W. Rochester for advice on analyses, L. Dutra for scientific comment, P. Rothlisberg for scientific writing advice, and L. Blamey for expert manuscript comment.Thank you ('Esso') to all Indigenous Torres Strait Islanders for hosting us on Kulkagal and Kemer Kemer Meriam nation's land and sea country, and for supporting this research.
Total number of zones and sites surveyed by year, including number of sites per habitat strata.
T A B L E 1 Implementation of western science and management, and Ailan Kastom traditional management, for Black teatfish fishery openings in Torres Strait.
T A B L E 3