ICES has fundamentally reworked the assessment method for both cod stocks. This is expected to improve the precision of the assessment, but requires a lot of explanations as a number of changes have been applied simultaneously. We briefly present the ICES advice for stocks of importance to the German fishery for 2016 and provide answers to some of the most important questions in relation to the advice below.
The original ICES advice can be found here, more elaborations will be available on “Fischbestände online” soon (in German). The advice is currently based on the ICES interpretation of the maximum sustainable yield (MSY) concept; the Baltic multiannual management plan which is currently negotiated might result in different total allowable catches (TACs), depending on the final agreement of this plan in autumn.
Herring western Baltic (22-24): The stock is now within the green range (biomass is large enough, fishing pressure low enough) for the first time in the (rather short) time series. This stock will remain healthy even with continued low fishing pressure, as the fishing pressure has been reduced sufficiently. If managed according to the MSY concept, stock and TAC will likely increase in the medium term. For 2016, ICES recommends that catches from the stock could increase by up to 18% (corresponding to no more than 52547 t), half of this (26274 t) can be caught in the western Baltic.
Herring central Baltic (25-27,28.2,29,32): The stock is within the green range for many years and continues to increase, the 2014 year class is considered strong. ICES advises on the basis of the MSY approach that catches may increase by up to 4%, corresponding to 210000 t total catch. Catches from this stock in the Gulf of Riga are added to catches from the Gulf of Riga herring stock to arrive at the herring TAC in the area Gulf of Riga. These are more than 4500 t annually, corresponding to 17% of herring catches in the GoR.
Sprat Baltic (22-32): The stock is still large enough but declined slowly over the last years. Fishing pressure increased significantly in the last year and is now above Flim. According to the MSY approach, catches will have to be reduced at least for next year, by 15% to no more than 205000 t (total catch). As the 2014 year class appears to be strong, stock size and catches are likely to increase from 2017.
Baltic flatfishes: Plaice: Is now assessed as two separate stocks, which could however be managed together. ICES presented an analytical assessment for plaice 21-23 for the first time; the stock increases quickly, ICES advises that catches could increase by 114% to no more than 8639 t, which corresponds to 4642 t landings (if the discard ratio remains constant). Plaice 24-32: data limited stock, advice: increase catch by max. 20% (maximum deviation from previous year) to 2156 t total catch, which corresponds to 1093 t landings. Flounder: Four stocks are defined in the Baltic Sea, all are data-limited and catches not limited by a TAC. Flounder 22-23: +20% to 3042 t total catch. Flounder 24-25: +20% to 28904 t. Turbot 22-32: -10% to 198 t.
Cod: ICES is now able to separate the two Baltic cod stocks, specifically in the mixing area, the Arkona Sea (SD24). At least for the western stock, it is now possible to conduct a stock-specific assessment. So far, both stocks have been assessed on a regional basis, i.e. all catches from SD24 have been attributed to the western stock, although it was known for quite some time that a significant fraction of the catch is of eastern origin. The consequence of this change is that the western cod appears much smaller, the eastern cod stock slightly larger. Reference points for the western cod have been updated, and abandoned for the eastern stock. Further, ICES now advises on a total catch including recreational catches. These significant catches of anglers have been included in the assessment since 2013 but then subtracted before an advice for commercial catches was given.
Cod western Baltic (22-24): This stock is overfished (biomass is below Blim) and fishing pressure is above Fmsy. ICES advises following the ICES MSY rule (which requires a linear additional reduction of fishing pressure if biomass is below MSY Btrigger) that total catch from the western stock should be less than 5385 t. Recreational catches would have to be subtracted from this advised catch to arrive at the commercial catch. To derive the total allowable catch for the western area (which is always area-based), assumed catch of eastern Baltic cod in SD24 would have to be added. Therefore, a direct comparison of this year’s advised catch and last year’s TAC are not possible. Depending on the decisions on target fishing mortality (with or without additional reduction), consideration of recreational catches and amount of eastern cod in SD24, the reduction of the TAC could be between 82 and 10%. The reduction in relation to the catch from the western stock in 2014 (2015 is still on-going and thus the catch from the stock cannot be determined) is 67%. The stock will likely develop positively: it will increase following any reduction of the catch, and with a reduction of 10% it is likely that the stock will be above MSY Btrigger in 2017 (if the same amount of eastern cod is available in SD24 as in 2014). To protect the western stock in 22-23, ICES advises to implement a sub-TAC which limits the catch from this area.
Cod eastern Baltic (25-32): ICES was again unable to conduct an analytical assessment for this stock, because major uncertainties in input data could still not be resolved. Science is intensively working on the validation of age reading and determination of growth rates. Until results are available, ICES continues to use research survey catch rates to determine the numerical advice: Catches of eastern Baltic cod (including those taken in SD24, which have not been included in this stock until this year) should be reduced by 32% (in relation to the advised catch 2014). This corresponds to 29220 t total catch, of which between 0 and 7121 t could be caught in the west. This amount would then have to be subtracted from the total catch by stock to arrive at the eastern Baltic cod. Only 53% of the 2014 TAC were taken, the discard ratio went up to 25% in 2014.