Acoustic Observations of Patterns of Aggregation in Haddock (Melanogrammus aeglefinus) and Their Significance to Production and Catch

1992 ◽  
Vol 49 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Paul R. Boudreau
Keyword(s):  
Body Size ◽  
Spatial Scales ◽  
Time Of Day ◽  
Melanogrammus Aeglefinus ◽  
Biomass Density ◽  
Dual Beam ◽  
Local Aggregation ◽  
Catch Rates ◽  
High Degree ◽  
Haddock Melanogrammus Aeglefinus

A dual-beam acoustic system was used to collect detailed information on density and body size over a 24-h period in an area of the Scotian Shelf occupied by a population of large spawning haddock (Melanogrammus aeglefinus). The acoustic sampling showed a persistent gradient of decreasing density with distance from bottom with 50% of the fish < 2.5 m off bottom. Horizontally (scale of hundreds of metres), there was a high degree of local aggregation which changed dramatically over 24 h. Highest aggregation was in daytime, with fish more dispersed throughout the water column at night. The differences in the degree of aggregation with time of day appear to be sufficient to explain diel changes in net catch rates. On larger geographic scales (tens of kilometres), fish density was relatively uniform. Acoustics provide a method for studying the relative importance of aggregation on these various spatial scales to estimates of abundance. Haddock biomass density was also related to organism body size, as has been observed for other species in both aquatic and terrestrial situations, suggesting that haddock population density is determined by trophic interactions similar to those that underlie production of other populations of organisms.

Maternal and seasonal differences in egg sizes and spawning activity of northwest Atlantic haddock (Melanogrammus aeglefinus) in relation to body size and condition

2004 ◽  
Vol 61 (11) ◽  
pp. 2097-2110 ◽  
Author(s):  
Edward A Trippel ◽  
Steven RE Neil
Keyword(s):  
Body Weight ◽  
Body Size ◽  
Egg Production ◽  
Condition Factor ◽  
Fertilization Rate ◽  
Melanogrammus Aeglefinus ◽  
Northwest Atlantic ◽  
Larval Production ◽  
Egg Diameter ◽  
Haddock Melanogrammus Aeglefinus

Egg and larval production of 22 captive spawning pairs of northwest Atlantic haddock (Melanogrammus aeglefinus) were monitored. Females spawned an average of nine egg batches (range 3–16) with a mean batch fecundity of 60 000 eggs and mean total fecundity of 535 000 eggs. Mean spawning duration was 37 days with a mean batch interval of 5.4 days. In multiple linear regression, male Fulton's condition factor (range 1.10–1.55) and mean batch interval explained 56% of variation in fertilization rate (33% and 23%, respectively). Seasonal composite egg diameter spanned 1.37–1.53 mm among females. Mean egg diameter within females declined seasonally by an average of 10.4% (37% by volume). Females produced 46 larvae per gram body weight. Body weight was the single best predictor of fecundity (r2 = 0.57), with Fulton's condition factor (range 1.04–1.76) explaining no significant additional variation over length or weight. Length and condition explained 39% of variation in seasonal composite egg diameter (22% and 17%, respectively) and body weight independently explained 32%. Sex-specific parental condition and body size acted through large egg size and elevated fertility to enhance reproductive output. Male spawning success was more sensitive than egg production to changes in condition.

Geographic Responses of Groundfish to Variation in Abundance: Methods of Detection and Their Interpretation

1994 ◽  
Vol 51 (4) ◽  
pp. 808-816 ◽  
Author(s):  
C. Tara Marshall ◽  
Kenneth T. Frank
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Horizontal Distribution ◽  
Melanogrammus Aeglefinus ◽  
Age Classes ◽  
Dimensional Distribution ◽  
Catch Rates ◽  
Positive Correlations ◽  
Haddock Melanogrammus Aeglefinus ◽  
Trawl Surveys

Recent published studies have used data from bottom trawl surveys of groundfish populations to test whether distributional area and abundance are correlated. Two studies that used different indices to represent the distributional area of Georges Bank haddock (Melanogrammus aeglefinus) yielded conflicting results. To determine whether this is an example of different distributional indices measuring different things, both indices were regressed against estimates of abundance of haddock from a different but neighbouring location on the southwestern Scotian Shelf. Positive correlations were observed for immature age-classes using both indices whereas only one of the two indices resulted in positive correlations for mature age-classes. The following factors contributed to the lack of agreement among distributional indices: (1) age-aggregated indices potentially obscure correlations between distributional area and abundance for individual age-classes; (2) distributional indices that depend on the magnitude of catch rates confound variation in the large-scale horizontal distribution of stocks with diurnal variation in the three-dimensional distribution of schools; (3) distributional indices that scale positively with abundance generate spurious correlations. The results suggest that the outcome of any test of whether distributional area and abundance are correlated depends on the index chosen to represent distributional area.

scholarly journals Selective flatfish seine: a knee-high demersal seine barely catches cod

2019 ◽  
Vol 76 (4) ◽  
pp. 1200-1208 ◽  
Author(s):  
Ólafur Arnar Ingólfsson ◽  
Odd-Børre Humborstad ◽  
Svein Løkkeborg
Keyword(s):  
Gadus Morhua ◽  
Time Of Day ◽  
Melanogrammus Aeglefinus ◽  
Night Time ◽  
Hippoglossus Hippoglossus ◽  
Northern Norway ◽  
Solea Solea ◽  
Fishing Gears ◽  
Vertical Opening ◽  
Haddock Melanogrammus Aeglefinus

Abstract Norwegian coastal cod (Gadus morhua) protection restricts the use of active fishing gears. Demersal seines, acknowledged as being efficient for targeting flatfish, are therefore largely excluded from the fjords. To exploit plaice (Pleuronectes platessa), a species-selective gear that avoids catching cod is needed. We therefore designed a low-rise demersal seine with a 0.6 m vertical opening and tested it on fishing grounds in Lofoten (Northern Norway), comparing it with a conventional seine that had a vertical opening of ∼3.5 m, and fished both during the day and at night. Six to nine hauls were taken with each of the four gear/time-of-day categories (32 hauls in total). The low-rise seine caught no fewer plaice during day-time fishing, but less at night. Cod and haddock (Melanogrammus aeglefinus) catches were reduced by 94% and 98%, respectively, while catches of sole (Solea solea) increased with the low-rise seine. No catch differences were found for halibut (Hippoglossus hippoglossus), common dab (Limanda limanda), or monkfish (Lophius piscatorius). The low-rise seine therefore enables targeting flatfish while avoiding gadoid catches, although loss of plaice during night-time fishing is to be expected.

scholarly journals A meta-analysis of vertical stratification in demersal trawl gears

2017 ◽  
Vol 74 (8) ◽  
pp. 1243-1250 ◽  
Author(s):  
R.J. Fryer ◽  
K. Summerbell ◽  
F.G. O’Neill
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Meta Analysis ◽  
Leading Edge ◽  
Time Of Day ◽  
Vertical Stratification ◽  
Melanogrammus Aeglefinus ◽  
Horizontal Distance ◽  
Merlangius Merlangus ◽  
Haddock Melanogrammus Aeglefinus

A meta-analysis is presented of fishing trials that use trawl gear with horizontal separator panels to direct fish into an upper or lower codend. The analysis is applied to eight North Atlantic species: the gadoids cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), and whiting (Merlangius merlangus), the flatfish lemon sole (Microstomus kitt) and plaice (Pleuronectes platessa), and monkfish (Lophius piscatorius) and Nephrops (Nephops norvegicus). The proportion of fish that rise above the separator panel decreases as the height of the leading edge of the panel increases for six of the eight species. Only monkfish and Nephrops have no significant dependency on panel height. Cod is the only species for which separation depends on the horizontal distance of the leading edge of the panel from the ground gear, with the proportion of cod going above the panel increasing the farther the panel is from the ground gear. The time of day only affects the separation of plaice, with a greater proportion going above the panel at night than during the day.

scholarly journals Body size, reef area and temperature predict global reef-fish species richness across spatial scales

2018 ◽  
Vol 28 (3) ◽  
pp. 315-327 ◽  
Author(s):  
D. R. Barneche ◽  
E. L. Rezende ◽  
V. Parravicini ◽  
E. Maire ◽  
G. J. Edgar ◽  
...  
Keyword(s):  
Species Richness ◽  
Body Size ◽  
Reef Fish ◽  
Fish Species ◽  
Spatial Scales ◽  
Reef Area ◽  
Reef Fish Species
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