Spawning grounds of haddock ( Melanogrammus aeglefinus ) in the North Sea and West of Scotland

Previous studies have shown that four commercially important demersal species, namely Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and European plaice (Pleuronectes platessa), spawn in distinct areas across the North Sea. Based on two comprehensive ichthyoplankton surveys in 2004 and 2009, the present study uses generalized additive mixed models to delimit these spawning grounds using the distribution of recently spawned eggs, investigates their relationship to specific environmental conditions, and examines egg dispersal during their development. Results indicate that presence–absence of early stage eggs is more related to temporal and topographic variables, while egg densities are closely linked with hydrography. Egg distribution patterns were relatively consistent during development and only changed near hatching. Compared with historic observations, the location of the spawning grounds appeared stable on the broad scale but centres of egg abundance varied between the surveyed years. Potential effects of long-term climate change and anthropogenic short-term disturbances, such as seismic surveys, on fish reproduction are discussed, pointing out the demand for multispecies studies on these issues.

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Discarding practices for commercial gadoids in the North Sea

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-029 ◽

1998 ◽

Vol 55 (7) ◽

pp. 1632-1644 ◽

Cited By ~ 39

Author(s):

Yorgos Stratoudakis ◽

Robert J Fryer ◽

Robin M Cook

Keyword(s):

North Sea ◽

Gadus Morhua ◽

Atlantic Cod ◽

Melanogrammus Aeglefinus ◽

The North ◽

The North Sea ◽

Merlangius Merlangus ◽

Using Data ◽

Species Specific ◽

Catch Composition

Understanding fishers' discarding behaviour, and anticipating their reactions to changes in the biological or regulatory characteristics of a fishery, are important for dealing with the problem of discarding. In this paper, we investigate the discarding of haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and Atlantic cod (Gadus morhua) in the North Sea, using data collected by scientific observers onboard Scottish demersal vessels. We describe discarding on each trip by species-specific discard curves and explore how these curves depend on biological and regulatory variables. There are large differences in the size of discarded fish between inshore and offshore areas, with offshore-operating vessels discarding larger fish (high-grading). Increases in legal landing size correspond to immediate increases in the size of discarded fish, particularly for haddock and cod in inshore areas. In general, discarding practices for haddock and cod are similar over time and consistent across gears, whereas decisions for the lesser valued whiting are more variable and can be affected by the catch composition.

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Mapping the spawning grounds of North Sea cod ( Gadus morhua ) by direct and indirect means

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.0201 ◽

2008 ◽

Vol 275 (1642) ◽

pp. 1543-1548 ◽

Cited By ~ 55

Author(s):

Clive J Fox ◽

Martin Taylor ◽

Mark Dickey-Collas ◽

Petter Fossum ◽

Gerd Kraus ◽

...

Keyword(s):

North Sea ◽

Hot Spots ◽

Egg Production ◽

Gadus Morhua ◽

Early Developmental Stage ◽

Spawning Grounds ◽

The North ◽

Moray Firth ◽

The North Sea ◽

Early Developmental

Despite recent evidence for sub-stock structuring, North Sea cod are assessed as a single unit. As a consequence, knowledge of sub-stock trends is poor. In particular, there are no recent evaluations of which spawning grounds are active. Here we report results from the first ichthyoplankton survey to cover the whole North Sea. Also, this survey, conducted in 2004, was the first to make extensive use of DNA-based molecular methods to unambiguously identify early developmental stage cod eggs. We compare the findings from the plankton survey with estimated egg production inferred from the distribution of mature cod in contemporaneous trawl surveys. Results from both approaches were in general agreement and showed hot spots of egg production around the southern and eastern edges of the Dogger Bank, in the German Bight, the Moray Firth and to the east of the Shetlands. These areas broadly coincide with known spawning locations from the period 1940 to 1970. We were, however, unable to directly detect significant numbers of cod eggs at the historic spawning ground off Flamborough (northeast coast of England). The results demonstrate that most of the major spawning grounds of cod in the North Sea are still active but that some localized populations may have been reduced to the point where it is now difficult to detect the presence of eggs in the plankton.

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The fish and shellfish resources in seas adjacent to the Outer Hebrides

Proceedings of the Royal Society of Edinburgh Section B Biological Sciences ◽

10.1017/s0269727000012860 ◽

1979 ◽

Vol 77 ◽

pp. 479-494

Author(s):

R. S. Bailey ◽

J. R. G. Hislop ◽

J. Mason

Keyword(s):

North Sea ◽

Fishing Effort ◽

Fish Stock ◽

Full Time ◽

The West ◽

Spawning Grounds ◽

The North ◽

Outer Hebrides ◽

The North Sea ◽

Fish And Shellfish

SynopsisThe demersal fishery in Hebridean seas is based mainly on haddock, whiting and cod, mostly from local spawning grounds, with some recruitment from the North Sea. An important seasonal fishery for dogfish is based on a highly migratory stock. All these stocks are probably fully exploited.Herring spawning grounds occur west and north of Lewis, and larvae drift eastwards to nursery areas, mainly in the North Sea. Enhanced recruitment in the late 1960s and an increase in fishing effort produced a large increase in landings but these have subsequently declined. The west coast herring fishery is subject to quota regulations for conservation. There are also important exploitable stocks of mackerel and sprats. Since 1971 an industrial fishery for Norway pout has taken a few thousand tonnes per annum.Shellfishing by small boats goes with crofting. Since 1962 the number of larger boats has increased with full-time fishing, particularly for Norway lobsters and lobsters. Exploitation has been helped by processing and lobster-holding facilities. Scallops and periwinkles are also important commercially and there are good prospects for cultivating oysters and mussels.By far the largest underexploited fish stock is blue whiting, which migrates south to spawn in March-April on the continental slope in depths of over 400 m to the west of Scotland. The spawning stock in this area is estimated to be 5-15 million tonnes. Sandeels may also occur in commercial quantities in some areas.

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