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FishEriEs

            Applying a New Ensemble Approach in



            Estimating Stock Status of Marine Fisheries


            around the World





             The exploitation status of marine fisheries stocks worldwide is of critical importance for food security, ecosystem conservation

             and fishery sustainability. Applying a suite of data-limited methods to global catch data, combined through an ensemble
             modeling approach, we provide quantitative estimates of exploitation status for 785 fish stocks. Fifty-three percent (414 stocks)
             are below Bmsy and of these, 265 are estimated to be below 80% of the BMSY level. While the 149 stocks above 80% of BMSY
             are conventionally considered “fully exploited,” stocks staying at this level for many years, forego substantial yield. Our results
             enable managers to consider more detailed information than simply a categorization of stocks as “fully” or “over” exploited. Our
             approach is reproducible, allows consistent application to a broad range of stocks and can be easily updated as new data become
             available. Applied on an ongoing basis, this approach can provide critical, more detailed information for resource management
             for more exploited fish stocks than currently available.




               The	 over	 exploitation	 of	 wild-  only	 have	 a	 gross	 characterization	 of
            capture marine fisheries directly impacts   status,	 which	 provides	 little	 guidance	  landings	 database.	 The	 FAO	 conducts	 a
                                                                                       regular	 stock	 status	 review	 focusing	 on
            ecosystem	 health	 and	 the	 food	 security,	  for	 new	 policy	 action.	 Here,	 we	 apply	 a	  biological  over  exploitation  as  defined
            livelihoods,	 and	 cultural	 identities	 of	  consistent,	 easily	 repeatable	 method	 for	  in  most  fishery-related  international
            coastal	 communities	 worldwide.	 The	  estimating	 more	 detailed	 quantitative	  treaties	(e.g.,	United	Nations	Fish	Stocks
            failure	 to	 sustainably	 manage	 some	  estimates	of	stock	status	across	both	data-  Agreement)  and  classifies  stocks  into
            fisheries  has  resulted  from  many  factors   rich and data-limited fisheries.  three	categories	based	on	expert	opinions:
            including  deficient  institutional  capacity   Currently,	 there	 are	 two	 primary	  under	exploited,	fully	exploited	(including
            and	 inadequate	 data	 collection,	 leading	  sources	 of	 information	 used	 to	 estimate	  stocks	 that	 are	 notionally	 within	 20%
            to	the	lack	of	regular	evaluations	of	stock	  the status of fish stocks. The first source   above	 or	 below	 the	 biomass	 that	 would
            exploitation	 status.	 Quantitative	 stock	  comes	from	abundance	estimates	derived	  support	 maximum	 sustainable	 yield,
            assessments	 are	 generally	 only	 available	  from	  analytical	  stock	  assessments,	  Bmsy)	and	over	exploited.	While	the	FAO
            for	 relatively	 “data-rich,”	 commercially	  developed  by  fisheries  scientists  around   stock	status	review	includes	more	stocks
            important  stocks  predominantly  fished   the	world	over	the	last	60	years.	The	data	  than	the	RAM	Legacy	database,	therefore,
            by	 developed	 countries.	 Recent	 studies	  requirements	for	these	sorts	of	quantitative	  providing	a	more	comprehensive	picture
            of  marine  fisheries  exploitation  status   stock	assessment	are	substantial	and	are	  of	 stock	 status,	 the	 methods	 used	 to
            in	 developed	 regions	 of	 the	 world	 have	  usually restricted to commercial fisheries   evaluate fisheries are more heterogeneous
            demonstrated that significant progress has   where	 there	 is	 the	 analytical	 capacity	 to	  and	 less	 transparent	 than	 the	 stock
            been made in managing marine fisheries.   apply	complex	stock	assessment	models.	  assessments	 found	 in	 the	 RAM	 Legacy
            However,	much	less	is	known	about	many	  There	 is	 a	 comprehensive	 compilation	  database.	 In	 particular,	 the	 reliance	 on
            smaller-	or	lower-valued	stocks	and	stocks	  of  fish  stock  assessments  maintained  in   expert	judgment	to	determine	these	status
            fished in both developed and developing   the	 RAM	 Legacy	 database.	 Most	 stocks	  estimates	 means	 that	 they	 are	 harder
            regions	of	the	world.                included	in	this	database	are	from	North	  to	 reproduce,	 even	 with	 a	 systematic
               Recent	 estimates	 of	 the	 current	 state	  America,	Europe	and	developed	countries
            and	 future	 trajectory	 of	 marine	 stocks	  in other regions, while small-scale fisheries   methodology.	Similarly,	the	estimates	are
                                                                                       categorical,	 which	 means	 they	 are	 less
            show  that  many  of  the  world’s  fisheries   and	 those	 in	 developing	 countries,	 are	  quantitative	than	those	from	a	traditional
            are	below	biologically	sustainable	biomass	  under	represented.            stock	assessment	and	may	provide	limited
            levels	relative	to	widely	accepted	reference	  The	 second	 source	 of	 information	  guidance	for	management	decisions.
            points.	Stocks	in	data-limited	regions	are	  used to infer fisheries stock status around   There	are	two	major	ways	to	improve
            often	in	even	poorer	condition	than	stocks	  the	world	comes	from	the	United	Nations	  estimates	of	individual	stock	status	at	the
            in	data-rich	regions.	For	these	important	  Food	and	Agriculture	Organization	(FAO)	  global	level:	(1)	through	improvements	to
            marine	 resources,	 managers	 may	 at	 best

            8                                                  SAARC                                            JUNE 2018
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