Myndgreining á lögun síldarkvarna til aðgreiningar á síldarstofnum í Norður-Atlantshafi

Við fiskveiðar er mikilvægt að þekkja mun á fiskistofnum. Atlantshafssíldin, Clupea harangus, er uppsjávarfiskur og skiptist í fjölmarga síldarstofna sem finnast víðsvegar um Norður-Atlantshaf og hafa ólík gotsvæði og stofnuppruna. Þessi rannsókn var gerð í samstarfi við íslensku Hafrannsóknarstofnunina sem liður í alþjóðlega síldarverkefninu HERMIX. Til þess að þekkja mun á fiskistofnum er notuð útlitsgreining á kvörnum og kannað hvort sú aðferð henti til þess að greina mun á stofnum en þessi aðferð hefur nýst vel við aðra fiskistofna. Notast var við tölfræðiforritið R og tilheyrandi fylgipakka í öllum útreikningum. Hér er borin saman síld úr tveimur stofnum, íslensku sumargotssíldinni og norsk-íslenska síldarstofninum. Samkvæmt niðurstöðum eru síldarkvarnir frá mismunandi löndum mjög ólíkar en einnig er mikill munur á einstaka kvörnum innan sömu svæða. Íslensku síldarkvarnirnar voru marktækt stærri þó þær væru yngri, líklega vegna þess að sjórinn í kringum Ísland er ætisríkari

Age and growth of the Norway lobster (Nephrops norvegicus) in Icelandic waters

A lack of extensive age information can lead to a poor understanding of life history and population dynamics. As with most crustaceans, Nephrops norvegicus (Linnaeus, 1758) was thought to shed all calcified body parts that could be used to determine age, during periodic moulting. Number of indirect ageing methods have therefore been developed to estimate age. Recently, a direct method to determine the age of crustaceans was developed using growth bands that are deposited in the eyestalk and/or the gastric mill ossicles as age indicator. In this study both indirect length-based methods (ELEFAN I) and new direct method were used to inspect temporal changes in growth of Nephrops in Icelandic waters. Two fishing grounds in Iceland were chosen for comparison (Eldey and Breiðamerkurdýpi sites). In recent years the mean size has increased considerably and small animals are almost absent in Icelandic waters. The estimated von Bertalanffy growth parameters from the length-based method varied between time periods and sites (L∞ = 83–104 mm CL and K = 0.04 – 0.15). Consistent bands were observed with the novel direct age determination method in the zygocardiac ossicle of the gastric mill which were found superior to other ageing structures. Nephrops have a long life span and the oldest observed Nephrops in this study was estimated to be 22 years old at carapace length (CL) of 86 mm. Site-specific estimated age-at-size curves were developed using growth band counts which suggest a higher growth rate at Eldey site. Comparison between band counts and size-at-age interpretation determined from older length-frequency analysis differ slightly with increased variations for larger animals. The novel direct age determination method has the potential to be immensely valuable for future stock assessment for Icelandic Nephrops.Upplýsingar um aldur lífvera eru mikilvægar til að skilja lífsögu þeirra og fyrir flest stofnstærðarlíkön. Leturhumarinn, Nephrops norvegicus (Linnaeus, 1758), líkt og önnur krabbadýr tapar svo til öllum hörðum vef við hamskipti en það eru þessi vefir sem nýtast til aldursgreininga hjá fiskum og sjávarspendýrum. Því hafa verið þróaðar margar óbeinar aðferðir til að áætla aldur en flestar af þeim byggðar á lengdardreifingum. Nýleg rannsókn sýndi fram á að harðir líkamspartar í augnstilkum og/eða magakvörn (e. Gastric mill) krabbadýra tapast ekki við hamskipti og eru þau hluti af líkamsbyggingunni allt til dauðadags. Við nánari athugun hafa fundist rákir í þessum hörðu vefjum sem benda til að þar sé að finna upplýsingar um vaxtarbönd sem eru tengd aldri. Í þessari rannsókn voru vaxtarþættir humars við Ísland áætlaðir með hjálp lengdadreifinga (ELEFAN I) og nýrri aðferð (talin vaxtarbönd) og niðurstöðurnar bornar saman við eldri rannsóknir á vexti ásamt frekari greiningu á lengdardreifingu humars, en undanfarin ár hefur meðallengd humra farið vaxandi og lítið hefur orðið vart við nýliðun. Vaxtaparametrar von Bertalanffy byggðir á lengdardreifingum frá öllum veiðislóðum og tveim samanburðarsvæðum (Eldey og Breiðamerkurdýpi) voru nokkuð breytilegir á milli svæða og tímabila (L∞ = 83–104 mm SL og K = 0,04–0,15). Nýja aldursgreiningaraðferðin var árangursrík, en skoðaðir voru humrar frá sömu svæðum og áður. Skýr bönd voru sjáanleg í zygocardiac hluta magakvarnarinnar og voru þau mun skýrari en á öðrum svæðum kvarnarinnar. Leturhumar er langlíf tegund og elsti humarinn var metinn 22 ára gamall, en hann var 86 mm á skjaldarlengd. Niðurstöðurnar gáfu til kynna að humrar á Eldeyjarsvæðinu hafi hraðari vöxt en þeir sem eru úr Breiðamerkurdýpi. Eldra aldursmati bar nokkuð vel saman við yngri humra, en hjá stærri dýrum ofmetur eldri aðferðin aldur þeirra. Nýja aldursgreiningaraðferðin býður upp á marga möguleika og gæti orðið mikilvægur liður í stofnmati humars í framtíðinni

Poleward spawning of Atlantic mackerel (Scomber scombrus) is facilitated by ocean warming but triggered by energetic constraints

The Northeast Atlantic mackerel is an income breeder with indeterminate fecundity, spawning in multiple batches at optimal temperatures around 11°C in the upper water column during February–July along the continental shelf from 36–62°N. Based on macroscopic staging of gonads (N ∼62000) collected in 2004–2021, we detected an on-going extension of spawning activities into the Norwegian Sea feeding area (62–75°N), reaching stable levels around 2012 onwards. This poleward expansion increased as more fish entered the area, whilst the maximum proportions of spawners concurrently dropped from about 75 to 15% from May to July. Detailed histological examinations in 2018 confirmed the macroscopic results but clarified that 38% of the spawning-capable females in July terminated their spawning by atresia. We suggest that increased access to suitable spawning areas (≥10°C), following ocean warming from 2002 onwards, functions as a proximate cause behind the noticed expansion, whereas the ultimate trigger was the historic drop in body growth and condition about 10 years later. Driven by these energetic constraints, mackerel likely spawn in the direction of high prey concentrations to rebuild body resources and secure the future rather than current reproduction success. The ambient temperature that far north is considered suboptimal for egg and larval survival.publishedVersio

Feasibility of using growth band counts in age determination of four crustacean species in the northern atlantic

The age information of commercially important species is crucial in fisheries management. Age of various fish and molluscan species has routinely been determined by counting annual growth bands deposited within the hard structures. In crustaceans such structures were previously believed to be lost and replaced due to molting. However, a technique was recently developed to use growth bands deposited in hard structure retained through molting as an age indicator. In the present study, the applicability of the novel technique is investigated for four crustacean species collected from Northern Atlantic for the first time: European lobster, Homarus gammarus (Linnaeus, 1758); Norway lobster, Nephrops norvegieus (Linnaeus, 1758); Atlantic rock crab, Cancer irroratus Say, 1817; and northern shrimp, Pandalus borealis (Kroyer, 1838). The gastric mill ossicles in the first three species were processed to show the growth bands while the eyestalk was used in the shrimp species. Four growth bands were visible in European lobster hatched in a Norwegian hatchery and maintained alive for four years before prior processing. Band counts in the other three species were identical to size-at-age interpretation determined from length-frequency analysis. Validation of the periodicity of annual deposition of growth bands is essential before applying the technique on a wider scale

Feasibility of using growth band counts in age determination of four crustacean species in the northern atlantic

The age information of commercially important species is crucial in fisheries management. Age of various fish and molluscan species has routinely been determined by counting annual growth bands deposited within the hard structures. In crustaceans such structures were previously believed to be lost and replaced due to molting. However, a technique was recently developed to use growth bands deposited in hard structure retained through molting as an age indicator. In the present study, the applicability of the novel technique is investigated for four crustacean species collected from Northern Atlantic for the first time: European lobster, Homarus gammarus (Linnaeus, 1758); Norway lobster, Nephrops norvegieus (Linnaeus, 1758); Atlantic rock crab, Cancer irroratus Say, 1817; and northern shrimp, Pandalus borealis (Kroyer, 1838). The gastric mill ossicles in the first three species were processed to show the growth bands while the eyestalk was used in the shrimp species. Four growth bands were visible in European lobster hatched in a Norwegian hatchery and maintained alive for four years before prior processing. Band counts in the other three species were identical to size-at-age interpretation determined from length-frequency analysis. Validation of the periodicity of annual deposition of growth bands is essential before applying the technique on a wider scale

Working Group of International Pelagic Surveys (WGIPS)

WGIPS met in January 2023 to combine and review the results of the annual pelagic ecosystem surveys and provide indices for the stocks of herring, sprat, mackerel, boarfish, and blue whiting in the Northeast Atlantic, Norwegian Sea, North Sea, and Western Baltic. Timing, coverage and methodologies were assessed and coordinated for the upcoming 2023 surveys.Progression on the update of the WGIPS survey manual (SISP 9) in the TIMES format continued, with an expected first draft to be submitted in spring 2023 and the completion planned within the present WGIPS reporting cycle.The group discussed the future and development of databases used by the group (the ICES DB and the PGNAPES database). The use of StoX and progress on TAF were reviewed during a joint session with the ICES Data Centre and the StoX development team.The biological sampling strategies in WGIPS surveys continue to be discussed and progress is being made on documenting the sampling strategies used in all WGIPS surveys in the new format of the sampling manual. The planned workshop on sampling strategies in the HERAS survey has been postponed until further progress is made on data availability for analysis.WGIPS reviewed progress in using genetic stock separation methods for splitting survey results to component herring stocks and assessed ways forward for the development of these methods whilst maintaining the integrity of the survey indices. The group encourages continued close collaboration of the ICES survey and assessment groups and institutes carrying out the genetic analysis work.WGIPS continues to follow progress on mesopelagic fish sampling in the International Blue Whiting Spawning Survey (IBWSS) through updates from the Ecologically and Economically Sustainable Mesopelagic Fisheries EU project (MEESO) and other developments within this area of relevance to the WGIPS surveys

Second Workshop on Stock Identification and Allocation of Catches of Herring to Stocks (WKSIDAC2; outputs from 2023 meeting)

Population identification plays an important role in the assessment of Atlantic herring (Clupea harengus). Several morphological/traditional methods have been applied in the past to split catches (both within survey and commercial samples) and to identify herring populations. However, in recent years advances in genomics have provided a robust and precise method to genetically identify herring populations. WKSIDAC2 reviewed the current status of genetic population identification for herring and outstanding issues affecting identification accuracy/success. The genetic methods using single nucleotide polymorphism (SNP) as genetic markers to identify herring population are considered appropriate. Depending on the region of interest, different sets of markers are used to identify herring populations. The differences in the set of markers have only minor influence on the population identification and can be negligible. However, it is recommended to choose sets of markers which will allow a direct comparison between institutes undertaking the classification. Furthermore, the review concluded that 26 different herring spawning populations can be currently identified using genetic methods in the northeastern Atlantic. However, future genetic studies may increase the number of identified populations and also provide a greater resolution for the spatial distributions. For example, from the genetic markers presented during WKSIDAC2, we are not able to genetically differentiate between Icelandic summer spawners, Faroese autumn spawners, and Norwegian autumn spawners. These three populations are currently combined as a single genetic unit. Future work incorporating whole genome sequencing data, is recommended to investigate this issue in more detail. In addition, of the 26 identified genetic populations only some can directly and uniquely be assinged to a particular stock (management unit) and for this reason WKSIDAC2 refrained from establishing such correspondence which is left for future work. Baseline samples of these 26 populations have been analyzed based on different sets of markers. Therefore, the baseline information cannot be shared directly between institutes. Also, it is recommended that a common method for analyzing baseline samples, as well as storing the genotypes in an open and public database is agreed. During WKSIDAC2, a general description of prerequisites for the implementation of population identification of herring was discussed and several options have been presented. A series of presentations provide potential solutions on how to implement population identification in current stock assessment models or during survey estimates. However, analyses of the optimal baseline requirements for stock assessment purposes, both for specific surveys as well as commercial catches is to be the subject of a new workshop WKSIDAC3, proposed for 2024. The aim of the workshop is to establish a simulation framework for estimating stock compositions based on genetics 1) to investigate differences between random or stratified sampling, and 2) to investigate inter-haul variability in surveys