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183 pages, figures, 6 annexes, The Working Group on Nephrops Surveys (WGNEPS) is the international coordination group for Nephrops underwater television and trawl surveys within ICES. This report summarizes the national contributions on the results of the surveys conducted in 2021 together with time series covering all survey years, problems encountered, data quality checks and technological improvements as well as the planning for survey activities for 2022. In total, 19 surveys covering 25 functional units (FU’s) in the ICES area and 1 geographical sub- area (GSA) in the Adriatic Sea were discussed and further improvements in respect to survey design and data analysis standardization and the use of recent technologies were reviewed. Due to the COVID-19 pandemic there were minimal disruptions to survey operations where one survey was not completed (GSA 17). A trial trawl Nephrops survey offshore Portugal was carried out on the new research vessel. Preliminary work on how to measure burrow system size was presented using high definition (HD) and standard definition (SD) image data. Further work on comparison of SD and HD indi- cates the change to HD system mounted with a different camera angle was not significantly different for two survey areas (FU 16 and FU 20-21). Automatic burrow detection based on deep learning methods continues to show promising re- sults where datasets from multiple institutes were used. The working group members have agreed to draft a roadmap for automatic system technology requirements with links to the Work- ing Group on Machine Learning in Marine Science (WGMLEARN) and current researchers. The working group is progressing plans for an international Nephrops Underwater television (UWTW) database to be established at the ICES Data Centre. End-users of UWTV datasets for epifauna reporting presented their work and showed the potential for adding value to the survey data, where many of the institutes are involved in providing data for similar research purposes

114 pages, figures, tables, 5 annexes, The Working Group on NephropsSurveys (WGNEPS) is the international coordination group for Nephrops underwater television and trawl surveys within ICES. This report summarizes the na-tional contributions on the results of the surveys conducted in 2020 together with time series covering all survey years, problems encountered, data quality checks and technological improve-ments as well as the planning for survey activities for 2021. [...]

85 pages, figures, tables, 5 annexes, The Working Group on Nephrops Surveys (WGNEPS) is the international coordination group for Nephrops underwater television and trawl surveys within ICES. This report summarizes the national contributions on the results of the surveys conducted in 2019 together with time series covering all survey years, problems encountered, data quality checks and technological improve-ments as well as the planned for survey activities for 2020. In total, 19 surveys covering 25 func-tional units (FU’s) in the ICES area and 1 geographical subarea (GSA) in the Adriatic Sea were discussed and further improvements in respect to survey design and data analysis, standardiza-tion and the use of most recent technology were reviewed. A new survey summary template by FU/GSA has been developed and adopted for future re-ports, which shall allow the data end users to extract the most relevant information on the survey results in a more easy way. Necessary actions and reviewer comments were addressed on the draft version of the Series of ICES Survey Protocols (SISP). Similarly, the working group reviewed the specifications for a Nephrops underwater TV database to be established at the ICES data centre and agreed on fur-ther action on this issue. First results from field studies on behaviour aspects of burrow emergence using bottom cages monitored by an automated camera system and on short-range migration using acoustic tracking are now available. Comparison of standard definition (SD) and high definition (HD) indicates the change to HD system mounted with a different camera angle may affect the detection rate and may thus require a revision of bias correction factors. New image reviewing software allows an easier way of an-notation of burrows than previous mosaicking methods, which has further advantages for inter-preting the results from different counters and for providing quality assured material for deep learning methods. The WG members agreed to collect information on burrow diameter size us-ing HD images and burrow annotation or mosaicking software because a change in the burrow size distribution may indicate recruitment events and the size of the burrow has an effect on bias correction factors in general. Automatic burrow detection based on deep learning methods applied to a test data set with an-notated burrow counts from a HD camera system showed promising results. The WG members were encouraged to provide more material with annotated burrow counts for further develop-ment of machine learning tools

Recruitment of central/eastern Baltic cod critically depends on favourable oceanographic conditions in the deeper basins of the Baltic Sea creating a suitable habitat for the development of early life stages. The decline in the size of the spawning stock since the mid-1980s initiated a series of investigations on recruitment, which were continued through a partial recovery of the stock in the mid-1990s. The principal factors influencing recruitment and recognized at present are: (i) the volume of water with temperature, oxygen and salinity conditions which meet the minimum requirements for successful egg development ('reproductive volume'); (ii) the age-structure of the spawning stock; (iii) the timing of spawning; and (iv) predation mortality on eggs due to sprat (Sprattus sprattus) and herring (Clupea harengus), as well as cod cannibalism. We relate recruitment at age 2 to parent stock size using updated time series of these variables, comprising the period 1966 to 1994. Spawning stock biomass and egg production are compared as measures of parent stock size. The influence of wind energy and zooplankton abundance on cod recruitment are discussed. A modified Ricker model is outlined explicity accounting for environmentally-induced oscillations around the two observed levels of cod stock size.

Estimates of the reproduetion volume of Baltic eod defined as the. total volume of water with salinity above 11 psu, oxygen coneentration above 2 mIlI and temperature above 1.5 °c are presented for the Bornholm Basin based on quasi-synoptie hydrographie surveys. The primary data set consisted of hydrographie observations recorded during 14 eruises in the period from 1991 to 1996 eovering a regular grid of 36 stations with a spacing of appr. 10 nm. This data set was supplemented by including two additional surveys from 1989 with 21 stations. A statistical method the objective analysis was applied to mup the horizontal distribution of the thickness of the spawning layer. Subsequently, the reproduetion volume was ealculated by basiri wide integration. Highly significant eorrelations (r ~ 0.89, p < 0.001) betwcen single point observations of the thickness of the spawning layer and the overall reproduetion volume in the Bornholm Basin was found for 4 stations loeated in the eentral part of the surveyed urea. Linear regression models for single stations and the basin wide reproduction volume were established representing different hydrographie scenarios from stagnation to inflow periods. The results are discussed with respect to a backward extension of the time series using historical single point observations.

The volume of water with suitable oxygen and salinity conditions for survival and development of cod/eggs in the eastern Baltie Sea varies significantly within and among years. It has recently been shown that this volume of water (nreproduetive volumen), in addition to spawning stock biomass, is a major factor determining recruitment success in this eod population. However, it is unclear which oceanographie mechanisms are responsible for variability in reproductive volume, and how these processes interaet on a seasonal and interannual basis. In this study, we use time series observations to identify inter-relationships between hydrographie and biological processes (e. g., inflows of North Sea water, winter mixing processes, production and decomposition of organic matter) influencing reproductive volumes from 1952-1992. A frequent pattern of seasonal variability in 4 eastern Baltic spawning areas includes a spring maximum which decreases during the summer, followed by an inerease during the fall-winter months. However, this general pattern is violated in many years, and the magnitude of the seasonality is more pronounced, in some spawning areas than others. \Ve have begun to analyse these patterns and interpret them in the context of other fluctuating components of the eastern Baltic pelagic ecosystem. Preliminary results show that reproductive volumes deerease by an average of 9 - 39% between May and August, and that the decrease in the spawning area most important to long-term recruitment (Bornholm Basin) is temperature-dependen1. The seasonal decline in the Bomholm Basin also tends to be larger and more variable after 1964 than in the previous 12-year periode These patterns of reproductive volume variability may be important to eod reproduetive success beeause of a long and variable spawning period.

Die 160. Reise von FS "Poseidon" vom 6. Juli bis 4. August 1989 bildet den Auftakt einer Serie fischereibiologischer Fahrten zur Untersuchungen der Rekrutierungs- und Interaktionsmechanismen bei grönländischen Seefischbeständen. Das Programm unter der Leitung von Prof. D. Schnack wird in enger Zusammenarbeit mit dem Grönländischen Fischereiforschungsinstitut und dem Institut für Seefischerei der BFA für Fischerei durchgeführt. Es soll wissenschaftliche Grundlagen für ein ökosystem-orientiertes Fischereimanagement im Seegebiet vor Grönland liefern.