Down for the count

Once again, hunters find them­selves ques­tion­ing whether the sci­ence of wa­ter­bird count­ing is really a valid mech­a­nism for es­ti­mat­ing the size and dis­tri­bu­tion of dy­namic and tran­sient wa­ter­bird pop­u­la­tions — winged war­riors con­tin­u­ally search­ing for suita

Field and Game - - NT GOOSE SEASON -

Goose hunt­ing in the North­ern Ter­ri­tory has been cut for the 2017 sea­son (which started on Oc­to­ber 27).

NT Min­is­ter for En­vi­ron­ment and Nat­u­ral Re­sources, Lau­ren Moss said a shorter sea­son and a daily bag limit of just three birds was based on sci­en­tific sur­veys in­di­cat­ing the res­i­dent pop­u­la­tion was se­ri­ously de­pleted and needed time to re­cover.

“The NT’S mag­pie goose pop­u­la­tion is the low­est on record at 725 000. This is a dra­matic 45 per cent re­duc­tion on 2016 and only a quar­ter of the 2012 pop­u­la­tion,” Min­is­ter Moss said, adding the al­le­ga­tion that the pre­vi­ous gov­ern­ment had ig­nored sim­i­lar ad­vice, which ex­ac­er­bated the prob­lem.

But talk to Ter­ri­tory hunters and they raise ques­tions about tran­sects flown, ar­eas counted or not counted, and the sim­ple fact that Mag­pie geese have wings — they fly away and may well fly back.

It echoes con­ver­sa­tions by duck hunters in the south­ern states last year when faced with an Eastern Aus­tralian Wa­ter­bird Sur­vey in­di­cat­ing a 34-year low in wa­ter­bird abun­dance gen­er­ally and games species abun­dance: “…well below long-term av­er­ages, in many cases by an or­der of mag­ni­tude.”

On the ground, tra­di­tional hunters were see­ing large num­bers of game birds and mul­ti­ple breed­ing events, and had no con­cerns about abun­dance.

Pro­fes­sor Richard Kings­ford’s sur­vey re­port noted a breed­ing in­dex at the sec­ond high­est level on record, and it was fairly ev­i­dent that the lack of abun­dance ob­served from the air wouldn’t be repli­cated on the ground. How­ever, NT sci­en­tists rec­om­mended a max­i­mum take in 2017 of 15 000 geese for recre­ational hunt­ing, and a max­i­mum of 5000 geese un­der crop pro­tec­tion per­mits.

When com­bined with an es­ti­mated an­nual indige­nous har­vest of 60 000 birds, the to­tal take for 2017 would be 80 000 geese.

The av­er­age har­vest is 100 000 birds, with 40 000 for recre­ation and crop pro­tec­tion. So, the ar­gu­ment here is whether re­duc­ing this take to 20 000 birds (2.76 per cent of the cur­rent es­ti­mated pop­u­la­tion), is jus­ti­fied.

White­head (1998) and Brook and White­head (2005) in­di­cate that a max­i­mum sus­tain­able har­vest of 5 per cent to 14 per cent over the long term would be vi­able.

An Abo­rig­i­nal tra­di­tional har­vest of 60 000 and a non-abo­rig­i­nal har­vest of, say, 40 000 birds, to­gether would be 13.81 per cent of the 725 000 es­ti­mated mag­pie goose pop­u­la­tion within the high range for a sin­gle sea­son.

The per­mit­ted use of 80 000 geese is 11 per cent of the es­ti­mated pop­u­la­tion.

This brings us back to var­i­ous fun­da­men­tal ques­tions: will the re­duc­tion in bag limit, sea­son and off­take have any di­rect im­pact on dy­namic pop­u­la­tions? What is the im­pact of hunt­ing: is it ad­di­tive to over­all mor­tal­ity and pop­u­la­tion dy­nam­ics? Does hunt­ing mor­tal­ity mat­ter to the over­all pop­u­la­tion dy­nam­ics? And what are the land­scape strate­gies to en­hance breed­ing habi­tat to re­build the pop­u­la­tion if it is needed?

Es­teemed in­ter­na­tional wildlife

bi­ol­o­gist Pro­fes­sor Gra­hame Webb be­lieves tin­ker­ing based on par­tial sci­ence and in­tu­ition needs to be ap­proached cau­tiously.

“Fluc­tu­a­tions in wa­ter­bird num­bers are the end re­sult of a mul­ti­tude of in­ter­act­ing fac­tors and vari­ables, some that can be con­trolled to some ex­tent (e.g. har­vest rates) and oth­ers which can­not (flood or famine),” he said.

“We rarely, if ever, know the com­plex in­ter­ac­tions which take place be­tween these vari­ables, nor the ef­fect of ‘tin­ker­ing’ with the vari­ables that we can con­trol (like sea­son length and bag lim­its). So, try­ing to ap­ply sci­ence to the prob­lem still comes down to wield­ing some­thing of a blunt in­stru­ment, with no real idea of whether it hits the tar­get.”

Pro­fes­sor Webb said a pa­per pre­pared for Field & Game Aus­tralia in 2004 in re­la­tion to game birds made a strong case for main­tain­ing a “con­stant” har­vest regime to de­ter­mine defini­tively what hap­pens, and how the pop­u­la­tion ad­justs, rather than al­ter­ing sea­sons and bag lim­its an­nu­ally, with no idea of whether these strate­gies have any im­pact on the pop­u­la­tion at all.

Adap­tive Man­age­ment (AM) works by iden­ti­fy­ing the best ap­par­ent way of link­ing avail­able data to de­ci­sions (gen­er­ally a rule-based model), which is then ap­plied to the man­aged sys­tem to al­low its per­for­mance to be mon­i­tored. Through this process of trial and er­ror, AM al­lows in­cre­men­tally bet­ter de­ci­sions about how to man­age hunt­ing sea­sons to evolve.

The re­port notes that the ap­pli­ca­tion of AM re­quires “…ab­so­lute agree­ment and com­mit­ment by stake­hold­ers to the process, and a fair de­gree of trust and risk tak­ing” and the avoid­ance of cos­metic “pre­cau­tion­ary mea­sures”, which in­ter­fere with the gath­er­ing of mean­ing­ful facts and date about how the pop­u­la­tion re­sponds to de­ple­tion.

“Risk and un­cer­tainty are in­te­gral parts of adap­tive man­age­ment, and ef­forts to counter any pos­si­ble or po­ten­tial risk, on the ba­sis of be­ing ‘pre­cau­tion­ary’, can be sci­en­tif­i­cally coun­ter­pro­duc­tive within an adap­tive man­age­ment pro­gram.”

The 2017 NT Goose Sea­son is an ex­am­ple of ex­treme cau­tion in the face of limited sci­ence (aerial wa­ter­fowl sur­vey), and per­haps a missed op­por­tu­nity to ob­serve how the pop­u­la­tion does re­spond if sub­jected to the same har­vest regime with re­gard to sea­son and bag lim­its. What­ever the es­ti­mated abun­dance in 2018, there will be no mech­a­nism for de­cid­ing whether it was due to man­age­ment in­ter­ven­tions or not. So, there is an in­tel­lec­tual cost as­so­ci­ated with tin­ker­ing with the har­vest regime.

Pro­fes­sor Webb also made the observation that the indige­nous har­vest would nat­u­rally de­crease in line with pop­u­la­tion de­cline be­cause geese would be harder to come by but the as­sumed take is still 60 000 re­gard­less of abun­dance.

Pho­tos; North­ern Ter­ri­tory Field & Game

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