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FishEriEs


        the	data	and	technical	capacity	available	to	  combinations	 of	 life-history	 traits,	 initial	  Here,	 we	 quantitatively	 estimate
        quantitatively assess fisheries at the local   depletion,	effort	dynamics,	and	length	of	  current biomass of global fisheries relative
        level and (2) through further refinements   the	catch	time	series	were	demonstrated.  to	Bmsy,	for	stocks	in	the	FAO	database.
        to	 methodologies	 that	 use	 widely	   A	recent	development	in	data-limited	  We	aim	to	provide	a	more	comprehensive
        available	 data	 (e.g.,	 globally	 available	  stock	 assessment	 methods	 has	 been	 to	  assessment	 of	 global	 and	 regional	 stock
        landings  data).  The  first  option  requires   combine	 the	 estimates	 of	 exploitation	  status	by	implementing	a	super	ensemble
        substantial	 new	 resources	 and	 expertise.	  status,	 B/Bmsy,	 where	 B	 is	 current	 stock	  approach	 to	 combine	 status	 estimates
        The	 second	 option	 is	 more	 immediately	  biomass	and	Bmsy	is	the	estimated	biomass	  obtained	 from	 four	 different	 catch-only
        attainable	and	a	range	of	new	approaches	  to	 result	 in	 maximum	 sustainable	 yield	  models.
        has	recently	been	developed,	which	have	  from	multiple	catch-only	models	in	a	super
        fewer	data	requirements	than	traditional	  ensemble.	 A	 super	 ensemble	 is	 “super”	  Methods
                                                                                      We	 applied	 the	 four	 catch-only
        quantitative	stock	assessments.	Here,	we	  because	 it	 combines	 the	 estimates	 from	  methods	to	785	FAO	stocks,	subject	to	the
        focus	on	these	approaches,	which	require	a	  multiple	models	by	calibrating	them	on	a	  criteria	described	in	Table	1.	We	applied
        time	series	of	removals	(catches)	and	basic	  dataset	with	known	or	trusted	properties.	  one	empirical	model,	the	panel	regression
        life	 history	 information.	 This	 enables	 us	  Estimates	 from	multiple	 models,	here	of	  approach	 (PRM),	 and	 three	 mechanistic
        to	obtain	more	complete	global	coverage	  B/Bmsy,	 are	 calibrated	 to	 known	 values	  models,	 which	 all	 assume	 the	 same
        of	 stock	 status	 than	 more	 data-intensive	  via	 a	 regression	 model.	 This	 allows	 for	  population	dynamics,	but	make	different
        quantitative	 stock	 assessment	 models,	  both	 weighting	 the	 individual	 models	  assumptions	 about	 uncertainty	 and	 the
        although	these	methods	are	still	subject	to	  based	on	their	accuracy	and	exploiting	the	  dynamics of fishing effort:
        many	limitations.                    covariance	between	individual	models	to	  (1)	 The	 Catch-MSY	 (Cmsy)	 model,
           In	particular,	estimates	of	exploitation	  generate	 more	 accurate	 and	 less	 biased	  which	 includes	 assumptions	 about
        status	 by	 catch-only	 methods	 can	 be	  estimates	of	B/Bmsy.	The	super	ensemble	  resilience.
        biased	 and	 highly	 uncertain	 largely	 due	  approach	is	common	in	the	weather	and	  (2)	 The	  Catch-Only-Model	  with
        to	 required	 simplifying	 assumptions.	  climate	forecasting	where,	for	example,	it	  Sampling-Importance	  Resampling
        The	 strengths	 and	 weaknesses	 of	 four	  has	been	used	to	improve	predictions	of	  (COMSIR).
        catch-only	 models	 using	 a	 full	 factorial	  wind	and	precipitation	in	Asian	monsoons	  (3)	 The	 State-Space	 Catch-Only	 Model
        simulation	 framework,	 which	 evaluated	  and	 improve	 global	 surface	 temperature	  (SSCOM).
        their	  performance	  under	  different	  forecasts.                          To	 obtain	 global	 estimates	 of	 stock

         Table 1: Numbers of “stocks” (i.e., fished taxa) per FAO statistical area under each data filter applied and regional B/Bmsy status estimates
         FAO Area                   Original no. of   Filter:          Filter: >20    Median        Percentage
                                    stocks in FAO:   species-level     years and      B/Bmsy for    of Stocks in
                                    3,630 total      taxa: 2,621 total   >1,000 t of   stocks in    analysis with
                                                                       catch: 785     analysis      B/Bmsy <1:
                                                                       stocks                       414 stocks
         FAO	Stocks	                100%	            69.9%	            66.1%	         NA	           52.7%
         Arctic	Sea	                7	               5	                NA	            NA	           NA
         Atlantic,	Antarctic	       40	              29	               NA	            NA	           NA
         Atlantic,	Eastern	Central	  281	            176	              63	            1.05	         0.44
         Atlantic,	Northeast	       379	             269	              96	            0.95	         0.57
         Atlantic,	Northwest	       211	             158	              60	            0.82	         0.70
         Atlantic,	Southeast	       194	             122	              33	            0.84	         0.76
         Atlantic,	Southwest	       250	             161	              54	            1.03	         0.43
         Atlantic,	Western	Central	  247	            157	              52	            0.84	         0.67
         Indian	Ocean,	Antarctic	   51	              34	               NA	            NA	           NA
         Indian	Ocean,	Eastern	     219	             108	              55	            1.13	         0.29
         Indian	Ocean,	Western	     322	             202	              40	            1.14	         0.33
         Mediterranean	and	Black	Sea	  255	          163	              51	            1.02	         0.49
         Pacific, Antarctic         24               13                NA             NA            NA
         Pacific, Eastern Central   190              111               31             1.00          0.52
         Pacific, Northeast         110              80                26             0.98          0.54
         Pacific, Northwest         223              131               90             0.82          0.67
         Pacific, Southeast         203              121               46             0.91          0.59
         Pacific, Southwest         209              126               38             1.02          0.47
         Pacific, Western Central   215              96                50             1.10          0.34
         Median B/Bmsy and probability of B/Bmsy pertain to stocks with species-level taxonomic resolution and with catch time series longer than 20 years and more than
         1,000 t of annual median catch. The first value in the last column is the ‘percentage of all stocks across all regions with B/BMSY <1’ in analysis.

        JUNE 2018                                          SAARC                                                   9
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