James Kennedy

James Kennedy
Marine and Freshwater Research Institute | MRI · Pelagic division

PhD

About

36
Publications
11,351
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646
Citations

Publications

Publications (36)
Article
Full-text available
Lumpfish (Cyclopterus lumpus) migrate from their offshore feeding areas to the 10 coastal areas of Iceland during March and April where they remain for several months before 11 spawning. Their movements during this time are poorly documented. Using the results of an 12 extensive tag-recapture study (the largest documented) which took place between...
Article
Full-text available
Ovary development in Greenland halibut (Reinhardtius hippoglossoides) is complex, with several cohorts of developing oocytes present during vitellogenesis; this is unusual for a determinate spawner. There are also speculations that Greenland halibut are not capable of spawning every year. To investigate this possibility, ovaries from Greenland hali...
Article
Full-text available
The fecundity of European plaice (Pleuronectes platessa) in the Irish Sea between 2000 and 2004 was estimated during the spawning season for fish in the three main spawning areas (Liverpool Bay, the Cumbrian coast, and the western Irish Sea) and one small spawning group on the west coast of the Isle of Man. Fecundity was also estimated during Septe...
Article
Full-text available
This study investigates the reproductive strategy, an important component in the estimation of stock reproductive potential, in Norwegian spring-spawning (NSS) herring (Clupea harengus), an iteroparous, extreme capital spawner, through the estimation of fecundity over a period of 3years including two complete maturation cycles and three spawning se...
Preprint
Full-text available
Lumpfish ( Cyclopterus lumpus ) is a transatlantic marine fish displaying large population sizes and a high potential for dispersal and gene-flow. These features are expected to result in weak population structure. Here, we investigated population genetic structure of lumpfish throughout its natural distribution in the North Atlantic using two appr...
Article
Lumpfish (Cyclopterus lumpus) are the target of commercial fisheries in several countries. However, the collection of biological data for stock assessment purposes is both logistically difficult and expensive. The fishery takes place far from major population centres, over a wide geographical area, and, the roe is extracted at sea and the carcass i...
Article
Full-text available
Here we challenge traditional views on the direction of change in teleost body condition and reproductive traits in response to abiotic and biotic factors by studying the data-rich, planktivorous Norwegian spring-spawning herring (NSSH), a member of the abundant Atlantic herring (Clupea harengus) stock complex. To test potential influential factors...
Article
Lumpfish, Cyclopterus lumpus L., has an extended ovary development period and a relatively long spawning season. It therefore seems unlikely that individuals spawning later in the season would be able to recover from spawning and develop their gonads in time to spawn during the early part of the season the following year. The hypothesis that indivi...
Technical Report
Full-text available
Cruise report from the International Ecosystem Summer Survey in the Nordic Seas (IESSNS) 28th June – 5th August 2019
Article
Full-text available
This report documents the fishery, assessment, and management of lumpfish (Cyclopterus lumpus) across its distribution range. Targeting lumpfish for their roe on a large scale began in the 1950s in Iceland and Norway and then in Canada in the 1970s and Greenland in the 1990s. When the fishery began, there were few regulations, but limits on vessel...
Technical Report
Full-text available
The International Ecosystem Summer Survey in the Nordic Seas (IESSNS) was performed within approximately 5 weeks from June 30th to August 6th in 2018 using six vessels from Norway (2), Iceland (1), Faroe Islands (1), Greenland (1) and Denmark (1). The main objective is to provide annual age-segregated abundance index, with an uncertainty estimate,...
Article
Full-text available
The reproductive biology of fishes impact many other components of their life history, and can influence their vulnerability to fisheries, therefore for more informed management, a good understanding is essential. For lumpfish (Cyclopterus lumpus), a semi-pelagic species found across the north-Atlantic and targeted by fishers for their roe, compreh...
Article
The female portion of the population of lumpfish (Cyclopterus lumpus) in Iceland is currently monitored using a biomass index calculated using catch data from the Icelandic spring groundfish survey (referred to as the spring survey). This has been controversial among lumpfish fishers who insist that the behaviour and variations in the migration of...
Article
Full-text available
Following general life history theory, immediate reproductive investment (egg mass × fecundity/body mass) in oviparous teleosts is a consequence of both present and past environmental influences. This clarification questions the frequent use of season-independent (general) fecundity formulas in marine fish recruitment studies based on body metrics...
Article
Fecundity of Norwegian coastal cod (NCC) was estimated at several locations along the coast of Norway. There was no significant difference in carcass weight, liver weight or potential fecundity (Fp) between Lofoten and Verrabotn (Northern region) or between Bømlo and Langesund (Southern region). Fish caught in the Northern region had a higher liver...
Article
Full-text available
Lumpfish (Cyclopterus lumpus) is a high latitude species most abundant in Arctic and sub-Arcticwaters of the North Atlantic. Vertical behaviour of this fish is unclear as it is often caught by both pelagic and demersal trawls. To gain greater insight into its behaviour, 41 female lumpfish caught during the Icelandic Groundfish Survey (IGFS) in Marc...
Chapter
Full-text available
The present chapter deals with the estimation of female fecundity in fishes, mostly teleosts. The chapter is organized in three main blocks. The first block is devoted to technical issues of fish fecundity measurements from fixation, preservation and treatment of ovarian material to automatic oocyte counts. The use of certain staining protocols for...
Article
Full-text available
There is the potential to exploit new markets if fishermen are able to land live shrimp (Pandalus borealis, Krøyer 1838). For this trade to be economically viable, a high survival rate during capture and storage is essential. This study investigates possible factors such as trawl duration, sorting, storage temperature, storage time, and storage den...
Article
In this study the reproductive investment of six populations of Atlantic herring (Clupea harengus) in Norwegian waters was contrasted in relation to trade-offs with body growth (relatively slow-relatively fast) and migration distance (stationary-migratory). Down-regulation of fecundity through the process of atresia as well as standardisation of fe...
Article
Spawning and nursery grounds are poorly described for the West Nordic stock of Greenland halibut (Reinhardtius hippoglossoides) and the entire stock is assumed to originate from a common spawning ground southwest of Iceland. Greenland halibut with hydrated eggs in their ovary were caught during a gillnet survey in 1995 in Greenland waters. This sug...
Article
Full-text available
Life-history theory suggests that animals may skip reproductive events after initial maturation to maximize lifetime fitness. In iteroparous teleosts, verifying past spawning history is particularly difficult; the degree of skipped spawning at the population level therefore remains unknown. We unequivocally show frequent skipped spawning in Northea...
Article
Full-text available
Marine ecosystems are changing; global warming-induced increases in water temperatures and fishing have caused truncated age structures and small sizes at maturity in many stocks. This may affect both populations’ total reproductive output and the link between population demography and recruitment, yet detailed information on fecundity regulation i...
Article
Full-text available
A laboratory study was undertaken to investigate whether Northeast Atlantic herring (Clupea harengus), i.e., Norwegian spring-spawning herring, exhibit a "sensitive period" during the feeding season in which ovary development is particularly susceptible to food availability and (or) energy reserves. Groups of herring received similar amounts of foo...
Article
Fecundity in several fish species is subjected to down-regulation by atresia so if fecundity is estimated many months before spawning, this will be an overestimation of the realised fecundity (actual number of eggs spawned). In order to get accurate measurements of fecundity it is important to have knowledge on when potential fecundity (estimated f...
Article
Full-text available
It is now considered important to monitor the fecundity of fish stocks as this provides an indi- cation of the Stock Reproductive Potential (SRP). There is currently very little data on the fecun- dity of the West-Nordic stock of Greenland halibut (Reinhardtius hippoglossoides), which includes Greenland halibut in Icelandic waters. In order to achi...
Article
Full-text available
To examine mechanisms that affect fecundity, atresia, and skipped spawning in Northeast Arctic cod (Gadus morhua), we conducted an experiment where wild-caught cod (>60 cm) kept under restricted food regimes were subjected to monthly biopsies and hormonal and physical measurements. The power of body weight as a fecundity proxy increased until the p...
Article
The effect of controlling food intake during the autumn, which is the time of late vitellogenesis, on fecundity, atresia and follicle and ovary growth was examined for plaice Pleuronectes platessa. Eighteen fish were kept in individual pens and either fed on a high or low ration diet. Fish which increased in whole body condition exhibited an increa...
Article
Maternal influences on various egg and larval characteristics were examined using plaice from the Irish Sea and Norwegian coastal waters. Thirty-nine batches of eggs were incubated during the spawning season of 2004 and 2005. Thirty-seven larvae from one batch were also monitored individually to examine the influence of egg size on larval size at h...

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Project (1)
Project
Lumpfish reproduction, migration and TAC advice.