CCAMLR

A proposal for a Marine Protected Area in the Ross Sea region has been submitted to CCAMLR and iteratively updated since 2012 consistent with Scientific Committee advice.  The purpose of this paper is to: 1)  identify previously submitted scientific documents supporting MPA planning in the Ross Sea region; 2) highlight relevant Scientific Committee advice to support or modify previous iterations of this proposal; and 3) update relevant maps, figures and analyses from previously submitted scientific papers to reflect the boundaries of the current MPA proposal and with updated fishery data, to assist evaluation of the current proposal.  

I made six sensitive runs of CASAL models (LENGTH/AGE_IUU_MODEL) for stock status assessments of Dissostichus eleginoides in research block C in Division 58.4.4 b following the recommendation during the latest WG-SAM meeting. The six models with three kinds of assumptions on IUU catch were arranged referring to WG-SAM-14/18 as follows: 1) catch at length/age models on the assumption of no IUU fishing occurrence (Len_1/AgeSing_1 models), 2) catch at length/age models with estimation of IUU catch within the model using disease mortality functionality (Len_2/AgeSing_2 models), 3) catch at length/age models on the assumption that 22 % of IUU catch to the total observed across Division 58.4.4 occurred in the block (Len_3/AgeSing_3 models). Single age-length key (ALK) was used for each age structured model. Selectivity and associated index for disease mortality were estimated for Len_2/AgeSing_2 models but the selectivity for IUU fishery was fixed for Len_3/AgeSing_3 models. The other common conditions among six models were set as follows: parameters for ALK (k, Linf and t0) were fixed; year class strength (YCS) was estimated; double-normal selectivity for legal fishery was estimated; mean-based weighting method was used for proportion-at-length/age and tag-recapture; uniform prior was used for initial biomass (B₀) estimate.

The MPD estimates of the initial and current spawning biomass and current vulnerable biomass were highest for models on the assumption of 22% of total IUU catch and lowest for models with assumption of no IUU catch for both size- and age structured models. The age structured models were higher in each kind of biomass than size structured models for each assumption of IUU catch condition.

Every model showed more convergence in MCMC posterior trace for B₀ compared to my previous versions. MCMC estimates for median biomasses became larger than the MPD ones for each model, but the difference between them was considerably smaller compared to my previous versions.

Further sensitivity runs derived from Len_1 model (LEN_1_DER_MODEL) were examined using eight options changing conditions, i.e. estimate/fix for given parameters, uniform-log prior for B₀, and multinomial-based weighting for proportion-at-length and/or tag-recapture. From the results, the smaller differences between MPD estimates of median B₀ and MCMC ones and more convergence in MCMC posterior trace for B₀ for the current LENGTH/AGE_IUU_MODEL runs compared to my previous versions seem to be due to the use of the mean-based weighting instead of multinomial-based weighting used in my previous versions.

This report does not yet address the investigation on likely fixed selection patterns for estimation of IUU catches for Len/AgeSing_2 models (para. 2.24 (iii) of WG-SAM-2014 report). I need advice about the methods during WG-FSA meeting.

I made two sensitive runs of CASAL catch at length models (LENGTH_MODEL) for stock status assessments of Dissostichus eleginoides in research block 5843a_1 in Division 58.4.3a for the years 2004/05 to 2012/13 following the recommendation during the last WG-SAM meeting. The two models are generally based on those with the same names in WG-SAM-14/17 as follows: 1) R.0.1 model without tagging events before 2008, and 2) R.1 model including all tagging events (years 2005-2012). These models were comprised of two fisheries split by depths of 1 200 m as the model in WG-SAM-14/17.  Number of longlines was used as (unknown) multinomial sample size for each model. The over-dispersion for the tag-recapture likelihoods was estimated using a mean-based weighting method for each model. The other common conditions between the two models were set as follows: year class strength (YCS) was fixed; parameters of ALK were fixed; parameters of selectivity for legal fishery were estimated; uniform prior was used for initial biomass (B₀) estimate.

The MPD estimate of B₀ was 464 and 772 tonnes in R.0.1 and R.1 models, respectively. The current vulnerable biomass was 647 and 1 201 tonnes, respectively. The median MCMC estimates for the biomasses (490 and 810 tonnes) were slightly higher than those by MPD for each model. MCMC posterior traces for B₀ seem to be rather convergent for each model.

Further sensitive runs for R.1 model (R.1_DER_MODEL) were examined using six options changing conditions, i.e. estimate/fix for given parameters, uniform-log prior for B₀, and multinomial-based weighting for tag-recapture. The difference of median estimate of B₀ between MPD and MCMC and the range of MCMC were considerably large for R.1_2 model, which used multinomial-based weighting for tag-recapture that lead to quite high value of dispersion.

In this document, we revise stock status assessments of D. eleginoides in research blocks C and D using CPUE analogy method, Petersen method and CASAL model, although the data of current season has not been validated and not used for the present analysis. We used updated reference area size for the CPUE method and altered natural mortality for the Petersen and CASAL methods. Detailed results using CASAL models in research block C are described in a separated document.

The estimated stock size in block C was 709, 401 and 850 tonnes in CPUE analogy method, Petersen method and CASAL Len_1 model (vulnerable biomass in 2013), respectively.

The stock sizes of D. eleginoides in block D is estimated at 948 tonnes only by using CPUE method, as the catch and tagging data in block D was not enough to be applied to Petersen method and CASAL models.

We propose to continue the current research operation for the next fishing season with the same survey design and sample size of 60 tonnes in order to further strengthen the stock assessments in the area.

In this document, we revised stock status assessments of D. eleginoides in research blocks 5843a_1 using CPUE analogy method, Petersen method and CASAL model, although the tagging data of current season has not been validated and not used for the present analysis. We used updated reference area size for the CPUE method. Detailed results using CASAL models in the research block are described in a separated document.

The estimated stock size in the block was 2 393, 394 and 647 tonnes in CPUE analogy method, Petersen method and R.0.1 model (vulnerable biomass in 2013), respectively. Predicted number of tag recaptures from the estimated stock sizes using the Petersen and CASAL methods was consistent with the observed number in 2013/14 season. However, these estimators were based on tags released and recaptured only at the western end of the block, as pointed out at the last WG-FSA meeting (paragraph 6.66 of SC-CAMLR-XXXII, ANNEX 6, 2013).

As for the recommendation on east and west separation of research block for management due to considerable difference of catch rates between the locations and concentration of effort in the west during the last WG-SAM meeting (para. 3.37 of WG-SAM-2014 report), we investigated the historical catch rates in relation to locations and depths by vessels. As a result, we found no significant differences of catch rates between east and west areas for principal vessels except one vessel which is mainly attributed to the concentration of effort in the west and the large difference of catch rates between the east and west during the latest seasons. Thus we consider that the above mentioned differences between the east and west areas were related to one specific vessel and not a general matter. As a sufficient number of sets have been conducted in the east area, it should be recognized that the area has finished its prospecting phase. Therefore, we believe that we do not need to separate the management in the area provided appropriate spread of effort over the bank for the vessel is ensured.

We propose to set the sample size at current 32 tonnes for at least 3 years, which is likely to result in sufficient tag recaptures to substantially refine the stock assessment, as well as constituting a sufficiently low risk harvest rate as suggested at the last WG-FSA meeting.

The stock size for a research block (5842_1) was estimated by the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes.

As we proposed at the last WG-SAM meeting, since we have yet to obtain enough evidence to estimate plausible stock size, and accordingly have yet to estimate appropriate catch limit, we propose to continue the current research operation for at least 3 years with the same sample size as decided at the last CCAMLR meeting in the current research block, in order to promote successful stock assessment. On the other hand, we preliminarily estimated a sample size for 2014/15 using the CPUE analogy method for block 5842_1. The result of calculation was consistent with the current sample size.

In addition, we propose to allow flexibility in cases of research operations under extraordinary adverse ice-conditions, as detailed in in the research plans for Subarea 48.6 in WG-SAM-14/01 (2014) and WG-FSA-14/XX (2014).

The stock sizes for five research blocks (5841_1, 5841_2, 5841_3, 5841_4 and 5841_5) were estimated by the Petersen estimator and the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes. The stock size using the Petersen estimator was generally different from that using the CPUE method in each block.

As we proposed at the last WG-SAM meeting, since we have yet to obtain enough evidence to estimate plausible stock size, and accordingly have yet to estimate appropriate catch limit, we propose to continue the current research operation for at least 3 years with the same sample size as decided at the last CCAMLR meeting in the current research blocks, in order to promote successful stock assessment. On the other hand, we preliminarily estimated sample sizes for 2014/15 using the CPUE analogy method for each block except for block 5841_5 where Petersen method was applied following the procedure recommended at the last WG-FSA meeting. The results of calculations were generally consistent with the current sample sizes.

In addition, we propose to allow flexibility (i.e. carried-over and buffer zone) in cases of research operations under extraordinary adverse ice-conditions, as detailed in in the research plans for Subarea 48.6 in WG-SAM-14/01 (2014) and WG-FSA-14/XX (2014).

The stock sizes for five research blocks (486_1, 486_2, 486_3, 486_4 and 486_5) were estimated by the Petersen estimator and the CPUE x seabed analogy method using updated CCAMLR C2 data and reference area sizes. The stock size estimate using the Petersen estimator was similar to that using the CPUE method (using Division 88.2H as a reference area) for Dissostichus mawsoni in block 486_2. However, the estimates using the Petersen estimator were different from those using the CPUE method in other blocks where the Petersen estimator was applicable. Predicted numbers of tag recaptures from the estimated stock sizes using the both Petersen and CPUE methods (using Division 88.2H as a reference area) were relatively consistent with the observed numbers for D. mawsoni in the block 486_2 for 2012/13 and 2013/14 seasons. However the predicted and observed numbers using either method were inconsistent for Dissostichus spp. in other blocks.

As we proposed at the last WG-SAM meeting, since we have yet to obtain enough evidence to estimate plausible stock size, and accordingly have yet to estimate appropriate catch limit, we propose to continue the current research operation for at least 3 years with the same sample size as decided at the last CCAMLR meeting in the current research blocks except in block 486_3, in order to promote successful stock assessment. On the other hand, we preliminarily estimated sample sizes for 2014/15 using the CPUE analogy method for Dissostichus spp. in all blocks generally following the procedure recommended at the last WG-FSA meeting. The results of calculations were generally consistent with the current sample sizes, except for D. eleginoides in blocks 486_1&2.

In research block 486_3, the number of observed recaptures, which was significantly lower than those predicted, can be a result of limited number of hauls (only 13 and 14 hauls in 2013 and 2014, respectively) associated with the small catch limit. Regarding relatively high CPUE in the area, we propose to increase the catch limit from current 50 tonnes to 100 tonnes under the exploitation rate of 3 % in order for succeeding in the tagging experiment.

In addition, we propose to allow flexibility (i.e. carried-over and buffer zone) in cases of research operations under extraordinary adverse ice-conditions, as detailed in WG-SAM-14/01 (2014).

Mitigating the adverse affects of commercial fishing on the environment is an integral responsibility of fisheries globally.  Efforts to reduce bycatch, to exploit previously unfavourable species and to carry out research on associated organisms have increased with time but charismatic megafauna tend to gain priority, despite their numbers being relatively low compared to fish bycatch species.  The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is widely recognized for its thorough and effective management of Southern Ocean toothfish fisheries, especially in eliminating incidental seabird mortality, but comparatively little research has been applied to the thousands of fish caught as bycatch annually.  Fish bycatch mitigation controls in toothfish fisheries have seen a relatively recent evolution through CCAMLR’s conservation measures but their effectiveness has not been thoroughly investigated. This study explores trends in fish bycatch of exploratory fisheries for toothfish within the CCAMRL Convention Area, from 2006–2013, relating observations to CCAMLR’s conservation measures.  We found a significant reduction in bycatch landings by weight and number of individuals across years, despite no significant reduction in fishing effort probably linked to changes in landings of skates.  Bycatch by weight formed 6.7% of total catch per year, however the number of individuals landed was at times double that of toothfish. Gear type comparisons indicate that autolines catch a greater diversity of bycatch species than Spanish lines and trotlines.