Stock assessment of jack mackerel (Trachurus murphyi): a non- homogenous stock and changes in catchability. Hugo Arancibia* and Liesbeth van der Meer** 2nd Meeting of the Scientific Committee / SP-RFMO Honolulu (Hawaii), Oct. 1-7, 2014 * : Universidad de Concepción (Chile) **: OCEANA NGO

QUESTIONS:  Why other stock assessment of jack mackerel ? - availabiliy vs. abundance  Why a non-homogenous stock ? - different abundance geographically - different selectivity And  Why changes in catchability? - there is information only for the commercial fleets - 30°S as a border - cpue doesn’t decline faster than the biomass (due to fleets become more and more efficient)

HYPOTHESIS 1: The peak of jack mackerel biomass, in the first decade of the 2000s, didn’t exist. (next)

Spawning stock biomass (x 10 3 ) of jack mackerel, 1970 – Source: Report Sci. Cttee., SP-RFMO.

HYPOTHESIS 2: Annual recruitments of jack mackerel from 1995 to 2000 or 2002 should be lower than the prediction of the SP-RFMO (next)

Recruitment of jack mackerel (number of fish x 10 3 ),

I n f o r m a t i o n

Catch of T. murphyi per geographical zone in the South Eastern Pacific Ocean. Nomenclature: ZNCh = off northern Chile; off central-southern Chile. Period: 1970 – 2013.

Table 1. Parameters and data considered in the stock assessment of T. murphyi (present study) AreaFisheryCatchAge/LengthCPUEAcoustic survey Eggs NorthPeru a Chile b Oceanic c SouthChile d Oceanic a: Segura and Aliaga (2013). b: Time series gaps: , 1991 and c: Catch in international waters adjacent to Chile and Peru belong to the Sub-Division North and Sub-Division South (Grechina 1998). Catch in the South Western Pacific Ocean was not incorporated in the assessment. d: T. murphyi acoustic surveys provide ichtyoplankton information and also spawning biomass estimations, which is assumed proportional to the spawning biomass..

Dynamic of the abundance (see text, pages 6 to 8) - recruitment, -total mortality, -SSB, -catch equation of Baranov, -growth parameters, -indexes of abundance (Table 2) -model was programmed using AD Model Builder Table 2. Indexes of abundance used in the assessment - acoustic biomass in Peru (*) – paper published in Peru - CPUE in CSZ Chile - CPUE in NZ Chile - acoustic biomass CSZ Chile - acoustic biomass NZ Chile - spawning biomass

Figure 11. Comparison between acoustic biomass estimations of T. murphyi in Peru (Segura and Aliaga 2013; in red) with biomass estimations used by the SPRFMO (Canales et al. 2013; in blue).

Model configuration (Table 3, pag. 10) -Structural assumptions involve in the log-likelihood functions of the base case in the stock assessment of T. murphyi. -catches, -catch at length (to avoid the length-age keys) -selectivity (2-years variations ) -abundance indexes (the same of RFMO, except acoustic in Peru) -The model was programmed using AD Model Builder

R E S U L T S

Figure 2. Total biomass (left) and spawning biomass (right) of T. murphyi stock by geographic zone (North: to the north of 30°S; South: to the south of 30°S). Period: 1975 to 2013.

Figure 3. Fishing mortality for T. murphyi by geographic zone.

Figure 4. Recruitment of T. murphyi by geographic zone. Period: 1975 to Horizontal lines represent quintiles at 75%, 50% and 25% respectively (both scales are different)

Figure 5. Total recruitment of T. murphyi where both geographic zones are included. Period: 1975 to Horizontal lines represent quintiles at 75%, 50% and 25%, respectively.

Figure 10. Potential reproductive ratio of T. murphyi. Period: 1975 to 2013.

C o n c l u s i o n s First hypothesis: The peak of jack mackerel biomass, in the first decade of the 2000s, didn’t exist.  Rejected. So, H1 must be accepted, i.e. the peak of biomass existed.  But, in a low level than the biomass (and abundnce) reported by the SP-RFMO in its last stock assessment. Second hypothesis: Annual recruitments of jack mackerel from 1995 to 2000 should be lower than the SP-RFMO reported.  Accepted. Annual recruitment strengths should be very low in the first years of the 2000s, and extremely low later.

Conclusions (cont.) The potential reproductive ratio of jack mackerel has been too low from 1996 (!), lower than 20%. (next) So, the present state of the jack mackerel stock is critical (and there is no possibility for restoration in the short and medium term). (next)

Figure 10. Potential reproductive ratio of T. murphyi. Period: 1975 to 2013.

Source: Cubillos et al. (2014), NZ Journal  Regime shift (strong ENSO strong La Niña ) + captures of juveniles has been too high

Thanks for your attention

Figure 8. cpue by vulnerable biomass of T. murphyi stock in the CSZ of Chile (upper left), NZ of Chile (upper right), and between catchability coefficient and vulnerable biomass in CSZ of Chile (lower left) and NZ of Chile (lower right).

Figure A5. Changes in vulnerable biomass estimations for T. murphyi by geographic zone: north and south (see text for explanations). Period:

Figure 9. Exploitation diagram of T. murphyi. Period 1975 to 2013.