This pre-core indicator and its threshold values are yet to be commonly agreed in HELCOM. The indictor is included as a test indicator for the purposes of the 'State of the Baltic Sea' report, and the results are to be considered as intermediate.
Monitoring relevant to the indicator is described on a general level in the HELCOM Monitoring Manual in the sub-programme: Fisheries by-catch.
Current national discard/by-catch monitoring programmes carried out under the EU data collection framework (DCF) do not target marine mammal and bird incidental by-catches. Monitoring under the EU council regulation 812/2004 protecting cetaceans against incidental by-catch (European Commission 2004) lays measures concerning incidental by-catches of cetaceans in fisheries using onboard observers but is limited to larger vessels and hence results in the lowest observer coverage of fisheries posing greatest threat to porpoises and seals in the Baltic Sea (ICES 2013a).
No regular monitoring activities relevant to the indicator are currently carried out by HELCOM Contracting Parties (see HELCOM Monitoring Manual in the Monitoring Concept Table).
Sub-programme: Fisheries by-catch
Monitoring Concept Table
All HELCOM Contracting Parties which are also EU Member States are obliged to carry out monitoring to provide estimates of population sizes in accordance with the requirements of the Habitats Directive and the Birds Directive.
Contracting Parties currently do not comply with Article 12 Habitats Directive as there is no monitoring in place that gives information that serves the target that incidental capture and killing does not have a significant negative impact on the species. Even more, current monitoring practice led to the unsatisfactory situation that the extent of the incidental by-catch problem is still not known and as a consequence only minor conservation measures regarding incidental by-catch (such as the use of pingers in a small fraction of the fishing fleet) are implemented. Some countries have been engaged in developing monitoring based on onboard video cameras recently. To date, it is not clear if this work (from pilot studies) will be extended to a monitoring programme on an annual basis and a representative fraction of the fishing fleets.
A monitoring programme is carried out under the EU Data Collection Framework (DCF). However, fishing métiers under DCF have been selected with respect to fishery data needs rather than bird and mammal incidental by-catch data needs. It is aimed at monitoring the selectivity of gears with respect to fish discarded and thus incidental by-catch of marine mammals and waterbirds are not even specifically addressed but rather recorded opportunistically at best. Only adding opportunistic incidental by-catch data to monitoring programmes focusing otherwise on size and (fish) species selectivity of certain fishing gears does not provide the needed data to enhance the confidence of the indicator. To some minor extent, waterbird incidental by-catch was monitored in Denmark, Germany, Poland and Sweden, while cetacean incidental by-catch was monitored under DCF in Denmark, Germany, Latvia, Lithuania, Poland and Sweden (ICES 2013a).
EU Regulation 812/2004 obliges Member States to monitor cetacean incidental by-catch in gillnets. It has been debated what gears are covered by the Regulation, as gear definitions were not formulated clearly enough for fisheries managers of some Member States (ICES 2010). This is why e.g. some Member States omitted monitoring of trammel nets (GTR) although it is known that porpoises are also by-caught in these nets (Pfander et al. 2012). Further, monitoring under Regulation 812/2004 is not suited to the data needs for this indicator or the original idea behind the Regulation because only vessels >15 m are covered by the observer programme and the majority of Baltic gillnet fisheries is carried out by small vessels which use the same gear. Vessels <15 m are allowed to set 9 km (vessel length <12 m) or even 21 km (vessel length >12 m) of gillnets, respectively, illustrating the high risk of incidental by-catch even by small vessels.
The Regulation also requires that Member States should design pilot schemes for small vessels; this has often not been done. The idea of scientific pilot studies is to give some indication on incidental by-catch numbers and provide information on what monitoring method might be suitable for small vessels, although cannot replace monitoring in this large fishing segment.
Only very limited data are collected for protected waterbird taxa under DCF, and it is not possible to estimate effort or coverage. Besides national differences there are large differences in coverage between fishing métiers favouring larger vessels and mainly trawlers. As a result, there are no agreed numbers of by-caught waterbirds and marine mammals for various types of fishing gear (mainly gillnets and entangling nets) in the Baltic Sea, because so far no adequate observer coverage has been achieved with existing monitoring programmes such as DCF and Regulation 812/2004. On the other hand, the results of pilot studies such as interviews are frequently questioned by fishermen and fisheries authorities. Especially in métiers which have been identified by pilot studies as fisheries with a high risk for mammal or bird incidental by-catch, monitoring is inadequate and a revision of existing monitoring programmes is urgently needed.
Monitoring of by-caught marine mammals and waterbirds should enable the estimation of annual (seasonal) mortality from all kinds of specific fisheries to be compared to the population dynamics of the respective species. Besides effort and incidental by-catch data, data on population size and delineation of sub-populations is also required in order to relate incidental by-catch numbers to the adequate population unit. Monitoring results should not only address the problem of incidental by-catch in general, but should allow to quantify impacts in order to propose management measures such as (temporary) closures of specific fisheries or fishing areas. Optimal monitoring would therefore also provide reliable population size estimates for all species considered from the incidental by-catch perspective.
The indicator requires estimates of population sizes for those species suffering from incidental by-catch. While such estimates are available for a number of marine mammals (especially seals) due to target-oriented surveys, they are quite crude for most waterbird species, especially those wintering in offshore areas. Further, uncertainties in population estimates and incomplete knowledge on spatial and temporal distribution patterns have to be addressed. Thus, internationally coordinated surveys need to be organized and should be embedded into the respective HELCOM abundance indicators.
The species covered by the indicator are highly mobile and fishing methods differ between sub-regions or even on a local level. Due to the resulting variability in incidental by-catch risk, a regionally and fishing method differentiated métier monitoring approach that considers fishing activity per spatial unit is recommended. A By-catch Risk Approach (BRA) can be used to identify areas and fisheries that are likely to pose the greatest conservation threat to incidentally caught species, taking into account the uncertainty of their population structure. A BRA was initially developed for cetaceans at an ICES Workshop (ICES 2010). It can also help optimising different methods of monitoring. The BRA highlights areas where the greatest problems occur and enables educated fisheries management decisions such as proactive mitigation measures before incidental by-catches occur. This is especially important for the critically endangered Baltic Proper harbour porpoise population.
Effort monitoring, as well as incidental by-catch monitoring, has to be carried out on a fine spatial scale in order to relate incidental by-catch to both fishing effort and abundance of mammals and birds. Fishing effort must be monitored in a meaningful parameter (length of nets * soak time instead of simply days at sea). The documentation of net length in the logbook (i.e. for vessels 10 m and longer) used is obligatory in EU fisheries since 2015 (EU Regulation of Implementation 2015/1962). Some national peculiarities apply. E. g. in Sweden, the coastal gillnet fishermen (vessels <8m in the Baltic marine region and <10m in the Atlantic marine region) are obliged to report their effort in meters*days for each gillnet type, mesh size and fishing location. Larger vessels are obliged to report number of nets, net length, and time for set and haul for each gillnet type, mesh size and fishing location. Since not all effort is recorded (small vessels, recreational net fisheries) and thus has to be estimated the uncertainty in the fishing effort estimates which underlie the incidental by-catch estimate needs then to be specified by adding a CV or 95 % confidence interval.
Appropriate monitoring is needed, so as not to put more burden than necessary on fisheries from management measures to fulfil legal conservation obligations. Monitoring must be able to cover all fisheries and all kinds of vessels. A comprehensive monitoring would use on-board and off-board observers, onboard CCTV cameras (also called Remote Electronic Monitoring, REM, Kindt-Larsen et al. 2012), and possibly additional methods such as interviews (ICES 2013b). In some cases, such as in fisheries with small open boats, self-sampling may be a component of the monitoring programme, but data quality must be verified independently.
Human observers are an important component to sample incidental by-catch and collect information on composition and number of incidental by-catch and to deliver specimen to the relevant authorities in order to conduct further examinations regarding age, sex, nutritional state, and injuries. In addition, stomach contents may help to identify in more detail the conflict between marine areas selected by fisheries and habitat demands of mammals and birds. Stranding networks can provide further incidental by-catch information if collected specimen are examined for net marks and previous injury which could have caused incidental by-catch. However, limitations in data quality have to be accounted for (e.g. beached bird surveys may indicate incidental by-catch but never give any information on the type of gear or nationality of the fishing vessel which caused the fatality).
ICES (2013a) has addressed the question of whether it is possible to combine monitoring of protected and endangered species and discard sampling (which will be the main focus of fishery monitoring due to the discard ban) in the same sampling scheme. However, it is unlikely that protected and endangered species will be kept on board or landed since this could infringe on existing national legislation of numerous Member States (ICES 2013a). As a minimum requirement, provisions must be taken that detailed, meaningful photographs of by-caught mammals and birds can be taken if landing is not possible.
It is hoped for that the knowledge on incidental by-catch of waterbirds and marine mammals will greatly be improved once a suitable monitoring scheme is implemented on regional and national levels within the revised DCF, now termed EU Data Collection Multi-Annual Programme DC-MAP: The DC-MAP will guide future fishery monitoring and data collection within the EU, covering a broad range of objectives including the discard ban. It is crucial that in the regional implementation process an adequate sampling coverage plan is developed including mammal and waterbird incidental by-catch in all relevant fisheries (commercial, part-time and recreational) in the Baltic Sea including all vessel sizes.
Pilot studies using cameras for monitoring harbour porpoise and bird incidental by-catch have shown that these have the potential to be a practical and economic tool for obtaining reliable incidental by-catch data. Further work is required to demonstrate the potential of the technique to perform consistently with regard to species identification and that all incidents are being detected (ICES 2013b). However, fishermen may reject these systems for personal reasons, hence research and international collaboration is needed on how to create a trustful attitude and to overcome personal reservations against onboard CCTV camera systems.
A main drawback of the onboard camera monitoring of bird and mammal incidental by-catch is that a large footage has to be viewed to verify the data from fishermen's protocols. In order to further reduce costs of a monitoring programme based on video observation, it may be helpful to computerize the work and view only preselected footage. Thus, the development and validation of reliable automated recognition systems for onboard camera systems is desirable.