Department of Primary Industries and Regional Development

Newsletter No. 36 October 2017

Welcome to the RAP Newsletter, providing feedback on the data you are collecting and keeping you informed about what is happening at the Division of the Department of Primary Industries and Regional Development. Status of southern garfish in the Perth region in 2010-2011 (Figure 1) and the proportion of aged more than two years fell from 30 % to less than 5%. The average length also declined. Considering the maximum reported age of 10 years for this species, the age structure of the Cockburn Sound stock in 2010-2011 was heavily ‘truncated’ Photo 1: Southern garfish. (i.e. older fish were absent from the In June 2017, the Perth metropolitan Cockburn Sound was in relatively population). area was closed to both recreational good condition. But, soon after this and commercial for southern study was completed, the abundance 60% garfish (Hyporhamphus melanochir) of garfish began a steady decline. In 50% to help the local population recover. response to this decline we began 40% n=294 We would like to thank those of you a major assessment of the stock in 30% who have been assisting us to monitor mid-2009. Most of our biological 20% 10% garfish by donating fish or recording sampling to determine age/length/sex Percent frequency logbook data. Your data is essential to composition of landings was 0% 0 1 2 3 4 5 6 7 8 9 10 our assessments. done in 2010-2011. We then spent Age (years) Fisheries Research Report 271 many hours in the lab trying to age the contains the results of our first garfish fish using the we had collected. stock assessment, completed in This was a challenge because garfish 60 2014 (http://www.fish.wa.gov.au/ otoliths are quite difficult to interpret, n=480 40 Documents/research_reports/frr271. although we eventually got the hang of it! pdf). Our assessments have been 20 updated annually since 2014 and the Proportion (%) latest findings are published in the 0 0 1 2 3 4 5 6 7 8 9 10 State of the Fisheries Report each Age (years) year. Here is a quick summary of our latest assessment. Figure 1. The age structure of southern garfish in Cockburn Sound in 1998 Slow decline since the late (previous study) (top) compared to 2009-2011 (bottom), showing the 1990s disappearance of older fish and Cockburn Sound has traditionally been a decline in the average age. Note: the Photo 2: Garfish egg found in Cockburn maximum age recorded for southern the main fishery for southern garfish Sound. Filaments used to attach the egg garfish is 10 years. in the West Coast Bioregion (WCB). to marine vegetation are clearly visible. About 80% of commercial landings and Garfish eggs are relatively large (3 mm The age data was used to estimate the 50% of recreational landings of this diameter). Photo: Jan Richards ‘instantaneous rate of total mortality’ species in the WCB have been taken in (Z) acting on the stock in 1998-1999 Cockburn Sound. We found the typical (most common) and 2010-2011. Z is equal to the age of garfish had declined, from sum of fishing mortality (F) plus natural A previous study in 1998-1999 two years in 1998-1999 to one year suggested the garfish population in mortality (M), i.e. Z = F + M.

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Continued from page 1 Garfish biology Southern garfish occurs across southern Z was estimated to be 0.90 per And then the heatwave Australia, including WA (Kalbarri year in 1998-1999 and 1.57 per struck…. southwards), SA, Victoria and Tasmania. year in 2010-2011 which, in non- It reaches a maximum length of 49 cm After our biological sampling in technical terms, means there was an and can live 10 years. Although this 2010-2011, we continued to annual survivorship (S) of 41% and species grows rapidly and attains maturity monitor catches and catch rates of 21%, respectively. Compared to the at a relatively young age (about a year), garfish in Cockburn Sound and the rate of survivorship experienced by it has some biological traits that make it broader Perth area. Commercial garfish ‘naturally’ (i.e. in an unfished relatively vulnerable to overfishing: population), which is 64% per year and recreational catch rates fell (Z = 0.44), the total mortality in sharply in 2012, and have remained Low fecundity: A female may 2010-2011 was extremely high. at historically low levels since multiple batches of eggs during spring This suggested that fishing pressure (Figure 3). Overall trends suggest a and early summer. Batch fecundity in Cockburn Sound increased very substantial (perhaps 70-90%) increases with size, ranging from about substantially between 1998-1999 reduction in garfish abundance in 100 eggs per batch for a small (22 cm) and 2010-2011, resulting in a 50% this area since the late 1990s. female to about 4,000 eggs per batch decline in survivorship. Recruitment failure during the for a large (40 cm) female. This is a low ‘heatwave’ event in summer 2010/11 level of egg production compared to many In our assessments, we tend to focus appeared to have caused the other fish species, which can produce on the rate of fishing mortality (F), dramatic decline in catches between tens of thousands or millions of eggs. rather than Z or M, because this is 2011 and 2012. Low fecundity limits how fast a garfish the factor that we actively manage population can recover from depletion. catch rate (fish/hour) (i.e. we can adjust catch and/or 0.6 Recreational commercial Small populations: In each region, fishing effort which will alter F, but 200 recreational 0.4 we can’t change natural mortality). southern garfish occur as multiple,

100 0.2 small, sub-populations. For example, In 2010-2011, the estimated F Commercial substantially exceeded the limit (kg/day) rate catch Cockburn Sound is believed to host its 0 0.0 reference point for this stock (Figure own sub-population. In SA, researchers 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 have found discrete (non-mixing) garfish 2). This level of fishing pressure is Year populations less than 60 km apart. This considered unsustainable. Figure 3: Annual commercial catch rate situation arises because garfish have (standardised) and recreational catch limited dispersal. Small populations are 1.5 rate of southern garfish in Perth area from 1996 to 2016, indicating a large more vulnerable to depletion (by fishing or decline in abundance since the late natural factors) than larger populations. 1.0 1990s, and very low abundance since Limited dispersal: Garfish eggs attach 2011. The recreational catch rate is to seagrass or other aquatic vegetation Flimit calculated from RAP logbook data, only 0.5 available from 2006 onwards (Note: via filaments on the egg (see Photo 2). Fthreshold Fishingmortality (F) Ftarget the commercial fishery voluntarily The larval stage is completed inside the ceased targeting garfish in 2016). egg, and they hatch as tiny juveniles 0.0 Female Male Both (~7 mm). Due to the attached eggs, and In summary, our assessment absence of a planktonic larval stage, there Figure 2: Rate of fishing mortality (F) indicates that the garfish stock in is no dispersal during these early stages. for southern garfish in Cockburn Cockburn Sound had been declining Juveniles and adults tend to remain Sound in 2010-2011, estimated since the late 1990s, mainly due using the age structure of males, associated with seagrass habitat too, females and both sexes combined. to an unsustainable level of fishing and so an individual fish might spend its Note: each F estimate, including pressure (both commercial and entire lifetime within the same seagrass 95 per cent confidence interval, recreational). The very depleted state bed. Limited dispersal means little mixing is well above the limit reference of the stock made it vulnerable to between populations. If a local garfish level for this species, indicating collapse after poor recruitment during population is depleted, it may take a an unacceptable level of fishing the ‘marine heatwave’. Five years pressure. Differences in F suggest long time to recover because it will not male garfish experience a slightly later garfish abundance remained be replenished by fish arriving from other higher rate of mortality than females. extremely low in the Perth area, and stocks. there was no sign of stock recovery. Dependency on seagrass habitat: These findings were consistent with This indicated that management Southern garfish are considered another part of the assessment which intervention was required to help this ‘seagrass-dependent’ because seagrass estimated that the spawning stock stock recover. With a fishing ban now forms a significant part of their diet and biomass of garfish had been greatly in place, we will continue to monitor their eggs must attach to seagrass (or reduced, to around 20% of the ‘virgin’ garfish over the next few years to similar vegetation) to survive. Garfish (unfished) level in 2010-2011. detect signs of recovery. generally live near seagrass or other marine vegetation all their lives. Seagrass habitat is threatened by human activities (such as dredging, water pollution) in many areas including Cockburn Sound. Blue groper attitude Jeff Norriss The recreational fishing community on WA’s south coast has a protective attitude toward the western blue groper that live along the coastline. Some southerners reckon there is something different about blue groper that makes them inherently vulnerable and, as a result, fishing for blue groper is not encouraged. So what is different about blue groper, compared to the average fish? Growing to 40 kg, blue perhaps due to fishing, one of the local females responds groper is southern Australia’s by changing sex to replace him. Blue groper are thought largest resident reef fish to have this flexibility because they are members of the (Photo 3). wrasse family and socially-induced sex change has been They are very long lived, demonstrated in other wrasse species. If this is true, the known to reach 71 years mid-thirties sex change is not hard-wired and strong fishing based on counts of annual pressure would result in a younger sex change. growth rings on their The blue groper’s diet is dominated by bottom-living otoliths (ear bones). They invertebrates. Preference has been tested experimentally by are inclined to take up divers offering three food choices: crabs were the preferred residence close to shore choice over greenlip abalone and spiny sea urchins. When and often remain within a feeding, blue groper sometimes make an audible crack small home range for years. as they carry out aggressive ram-and-bite manoeuvres to This has been demonstrated dislodge abalone, limpets and chitons clinging tightly to in South Australia through the reef. Their teeth are not the fine, needle-sharp teeth of the attachment of acoustic fish predators like tailor. Rather, they are like small pointed Photo 3: The official Australian tags (the same kind used in bolts, good for wrenching shellfish off rocks or punching record for the largest western WA and elsewhere to detect holes in them (Photo 4). Finally, strong crushing plates in blue groper is this 39.48 kg white ) that alert a specimen taken September their throat grind the food, including the shell, before it listening station if the tagged 1969 near Hopetoun by David enters the stomach (Photo 5). The shells of certain whelks Hopkins. fish swims within a few are incredibly strong, but a blue groper has the ability to hundred metres of it. Living pulverise them and expel the larger shell fragments through close to shore makes them accessible to divers, to whom their gills before swallowing the meat. large blue groper are either indifferent or inquisitive. Thus, large old fish are consistently vulnerable to spear or line fishers, and the south coast fishing community recognises this. This protective attitude is very apparent at the major annual fishing tournaments in Esperance and Albany – both of which exclude blue groper. It is not surprising therefore that the recreational catch is quite low. Only 104 fish were taken from the south coast in 2013-14, based on a Department of Fisheries survey of boat-based recreational fishing.

Bag and size limits - Western blue groper Minimum Individual species daily bag limit legal size West Coast Other bioregions Photo 4: The lips on this blue Photo 5: Robust grinding plates 500 mm 1 1 groper have been removed to in the throat can crush the reveal strong bolt-like teeth toughest shellfish. There are other extraordinary aspects of blue groper biology. for wrenching abalone and limpets from the reef. All start life as green coloured females, reaching sexual maturity at about 17 years old. Later in life, some change When their preferred food sources are scarce, blue groper sex and colour to become blue males, but not until their visit meadows of green macro algae named Caulerpa, where mid-thirties! Males grow larger. Colour is a reliable guide they take regular suction-bites out of the bottom, filtering to sex, so if the fish is blue it’s male and probably over 30 out tiny (1-2 mm) crustaceans from the detritus-rich habitat. years of age. Although nowhere near as nutritious as crabs, abalone and Sex change is likely to be brought on socially, although such, this ‘meadow grazing’ may be crucial when other food this is not confirmed. It is thought that if a male dies, sources are scarce. Continued on page 4 engagement andfuturepossibilitiesforRedmapAustralia. progress inrelationtoitskey objectives ofmonitoringand aboutthedevelopment ofthisproject,Our stafflearnt its change, usingthepublic’s owndata. engaging thepubliconecologicalimpactsofclimate environmental change(‘range shifts’).Thesecondis may beextendingtheirgeographicdistributiondueto detectionofspeciesthat monitoring fortheearly isecological Redmap hastwomainobjectives.Thefirst operating atanationallevel forfouryears. been now onthisprojectthathas We areapartner happening toouroceanspeciesasthewater warms. Professor Pecl whatis andherteamtodetermine ofmarinespecies.ThishelpsAssociate observations Australia tosubmitphotographsanddataaboutunusual recreational fishers, fromaround andbeachcombers divers www.redmap.org.au), acitizenscienceprojectthatinvites (Range ExtensionDatabaseandMappingproject, Associate ProfessorPecl headsaprojectcalledRedmap and AntarcticStudies, ofTasmania, University GretaPecl. Associate DeanofResearchattheInstituteforMarine staffrecentlyattendedaseminarby theDeputy Fisheries our marineenvironment Redmap –citizenscientistsmonitoringchangesin dive withalargebluegroperthattakes upresidenceinthe growing uponthesouthcoastwholoves to boy a about by famousWA authorTimWinton, entitledBlueback.It’s School, includesabook currently theEnglishcurriculum on totheyoungergeneration.AtAlbany SeniorHigh continue? Thatwillrequirethefishingculturetobepassed So, willthisprotectiveattitudeonthesouthcoast community hascontributed. No doubttheprotectiveattitudeoflocalfishing revealedgroper by stockstobehealthy. Fisheries however, isthatarecentassessmentofsouthcoastblue behaviour.late maturityandsedentary Thegoodnews, inherently vulnerabletoover-fishing due totheirlongevity, species,recognising thatbluegroperisaremarkable The southcoastfishingcommunityisindeedrightin Continued frompage 3 www.fish.wa.gov.au/frames ABN: 18951343 745 Drive,Deliveries: 39Northside Hillarys,Western Australia6025 Telephone: +61(08)92030111 Email: [email protected] David Fairclough, BrettCrisafulli, ElaineLek, Rhys AllenandKimClayton West Team CoastDemersal Kim Smith, AmberQuinn, ChrisDowlingandTimLeary Research andEstuarineFinfish Nearshore Team andhappyThank you fishing! foryour ongoingsupport understanding ouroceanspeciesandclimatechange. understanding significant contributions by citizenscientiststowards better their RedmapAustraliaproject, highlightingtheproject’s Science EurekaPrizeforInnovation inCitizenSciencefor ofIndustry,nominated fortheDepartment Innovation and Associate ProfessorPecl andherteamwere recently attitude oftheirown. experienced, bluegroperhave probablycultivatedsome of themchangesexalongtheway. Withallthey have topickupfoodscraps.Andsome feeding whitesharks intent,with predatory aswell aswithhumans.They follow interact withsealsthatchasethem, moreinplay than toreachhiddenprey Theyto rollboulders underneath. Perhaps we canfillinsomegaps?Bluegroperknowhow fish knowsandwhatithasexperiencedinitslifetime. In Blueback, theboy deeplyaboutwhatthe ponders attitude. school, andhisbookpassesontheprotectivecommunity Winton himself high moved toAlbany theyearhestarted cutoutprotectingthefishfromvariousthreats. has hiswork bay infrontofhishome.HenameshimBlueback, but soon

448/17 Illustrations © R.Swainston/www.anima.net.au