Acoustic markers of Atlantic cod (Gadus morhua) spawning in coastal Newfoundland

Knickle, D. Craig; Rose, George A.

doi:10.1016/j.fishres.2012.05.013

Cited by 8 publications

(9 citation statements)

References 34 publications

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“…We were unable to make direct observations of large numbers of cod using the ROV. However, the large shoals of fish interpreted as cod were consistent with the descriptions of cod spawning aggregations from the literature [19]–[22] and the DIDSON data revealed behavioral patterns consistent with that reported for spawning cod.…”

Section: Discussionsupporting

confidence: 88%

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Characterization of Atlantic Cod Spawning Habitat and Behavior in Icelandic Coastal Waters

et al. 2012

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The physical habitat used during spawning may potentially be an important factor affecting reproductive output of broadcast spawning marine fishes, particularly for species with complex, substrate-oriented mating systems and behaviors, such as Atlantic cod Gadus morhua. We characterized the habitat use and behavior of spawning Atlantic cod at two locations off the coast of southwestern Iceland during a 2-d research cruise (15–16 April 2009). We simultaneously operated two different active hydroacoustic gear types, a split beam echosounder and a dual frequency imaging sonar (DIDSON), as well as a remotely operated underwater vehicle (ROV). A total of five fish species were identified through ROV surveys: including cusk Brosme brosme, Atlantic cod, haddock Melanogrammus aeglefinus, lemon sole Microstomus kitt, and Atlantic redfish Sebastes spp. Of the three habitats identified in the acoustic surveys, the transitional habitat between boulder/lava field and sand habitats was characterized by greater fish density and acoustic target strength compared to that of sand or boulder/lava field habitats independently. Atlantic cod were observed behaving in a manner consistent with published descriptions of spawning. Individuals were observed ascending 1–5 m into the water column from the bottom at an average vertical swimming speed of 0.20–0.25 m s−1 and maintained an average spacing of 1.0–1.4 m between individuals. Our results suggest that cod do not choose spawning locations indiscriminately despite the fact that it is a broadcast spawning fish with planktonic eggs that are released well above the seafloor.

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Section: Discussionsupporting

confidence: 88%

“…Upon location of an aggregation, identified by characteristic echogram patterns [19]–[22], we cruised approximately 300–500 m up current of that position and lowered the DIDSON. The ROV was deployed if conditions on the bottom were favorable for recovery.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Atlantic Cod Spawning Habitat and Behavior in Icelandic Coastal Waters

et al. 2012

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“…Densities within this school ranged up to 1 fish·m −3 . In all surveys since 2008, large spawning aggregations, replete with pelagic columns and stacks (Rose 1993;Mello and Rose 2009;Knickle and Rose 2012), have been repeatedly observed (Figs. 2c, 2d).…”

Section: Resultsmentioning

confidence: 87%

Northern cod comeback

Rose

Rowe

2015

Can. J. Fish. Aquat. Sci.

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Abstract:The great "northern" cod (Gadus morhua) stock, formerly among the world's largest and the icon for depletion and supposed nonrecovery of marine fishes, is making a major comeback after nearly two decades of attrition and fishery moratorium. Using acoustic-trawl surveys of the main prespawning and spawning components of the stock, we show that biomass has increased from tens of thousands of tonnes to >200 thousand tonnes within the last decade. The increase was signalled by massive schooling behaviour in late winter first observed in 2008 in the southern range of the stock (Bonavista Corridor) after an absence for 15 years, perhaps spurred by immigration. Increases in size composition and fish condition and apparent declines in mortality followed, leading to growth rates approaching 30% per annum. In the spring of 2015, large increases in cod abundance and size composition were observed for the first time since the moratorium in the more northerly spawning groups of this stock complex. The cod rebound has paralleled increases in the abundance of capelin (Mallotus villosus), whose abundance declined rapidly in the cold early 1990s but has recently increased during a period of warm ocean temperatures. With continued growth in the capelin stock and frugal management (low fishing mortality), this stock could rebuild, perhaps within less than a decade, to historical levels of sustainable yield. More generally, if this stock can recover, the potential exists for recovery of many other depleted stocks worldwide.Résumé : Le grand stock de morues (Gadus morhua) du Nord, qui figurait parmi les plus importants du monde et constitue l'exemple type de l'effondrement et du non-rétablissement présumé de poissons marins, fait un grand retour après presque deux décennies d'attrition et de moratoire sur la pêche. À partir de relevés acoustiques et au chalut des principaux composants pré-reproducteurs et reproducteurs du stock, nous démontrons que la biomasse a augmenté de quelques dizaines de milliers de tonnes à >200 000 tonnes durant la dernière décennie. Cette augmentation a été signalée par le comportement de rassemblement massif en bancs à la fin de l'hiver, d'abord observé en 2008 dans la partie sud de l'aire de répartition du stock (corridor de Bonavista) après une absence de 15 ans, qui a peut-être été favorisé par l'immigration. Des augmentations de la taille et de l'embonpoint des poissons et des diminutions apparentes de la mortalité ont suivi, menant à des taux de croissance annuels approchant les 30 %. Au printemps de 2015, de fortes augmentations de l'abondance et de la taille des morues ont été observées pour la première fois depuis le moratoire dans les groupes reproducteurs plus septentrionaux de ce complexe de stocks. Ce rebond de la morue a accompagné des augmentations de l'abondance du capelan (Mallotus villosus), qui avait diminué rapidement durant la période froide du début des années 1990, mais qui a récemment augmenté pendant une période de températures océaniques plus chaudes. La croissance contin...

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“…The cod in Smith Sound, discovered in 1995, form the largest known spawning aggregation in the northern cod stock complex. Despite recent indications that the Smith Sound stock has reduced substantially in size [12], its anomalously high abundance and patchy nature have attracted significant research attention, including monitoring of Smith Sound annual adult biomass [43]–[45] behavioural studies [18], [44], [46], [47], measurements on physiological traits [17] and speculation on the spatial and temporal origins of the stock [12]. As is common for other harvested fish populations worldwide, however, little detailed information exists on dispersal and connectivity of egg and larval stages so important in determining overall population viability.…”

Section: Discussionmentioning

confidence: 99%

“…The role of this large spawning aggregation in potential recovery of stocks at local or large scales drew considerable attention [12], [15], [16]. Although previous researchers explored topics such as genetic isolation [12], recruitment success [16], reproductive biology [17], and spawning characteristics [18], [19] in the region, no study has detailed early life history dispersal originating in, and propagating away from Smith Sound. The dispersal characteristics of eggs and larvae leaving the Sound remain unresolved, and by closing this gap we begin to address how this large spawning aggregation connects at various spatial scales.…”

Section: Introductionmentioning

confidence: 99%

Factors Regulating Early Life History Dispersal of Atlantic Cod (Gadus morhua) from Coastal Newfoundland

et al. 2013

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To understand coastal dispersal dynamics of Atlantic cod (Gadus morhua), we examined spatiotemporal egg and larval abundance patterns in coastal Newfoundland. In recent decades, Smith Sound, Trinity Bay has supported the largest known overwintering spawning aggregation of Atlantic cod in the region. We estimated spawning and dispersal characteristics for the Smith Sound-Trinity Bay system by fitting ichthyoplankton abundance data to environmentally-driven, simplified box models. Results show protracted spawning, with sharply increased egg production in early July, and limited dispersal from the Sound. The model for the entire spawning season indicates egg export from Smith Sound is 13%•day−1 with a net mortality of 27%•day–1. Eggs and larvae are consistently found in western Trinity Bay with little advection from the system. These patterns mirror particle tracking models that suggest residence times of 10–20 days, and circulation models indicating local gyres in Trinity Bay that act in concert with upwelling dynamics to retain eggs and larvae. Our results are among the first quantitative dispersal estimates from Smith Sound, linking this spawning stock to the adjacent coastal waters. These results illustrate the biophysical interplay regulating dispersal and connectivity originating from inshore spawning of coastal northwest Atlantic.

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Acoustic markers of Atlantic cod (Gadus morhua) spawning in coastal Newfoundland

Cited by 8 publications

References 34 publications

Characterization of Atlantic Cod Spawning Habitat and Behavior in Icelandic Coastal Waters

Characterization of Atlantic Cod Spawning Habitat and Behavior in Icelandic Coastal Waters

Northern cod comeback

Factors Regulating Early Life History Dispersal of Atlantic Cod (Gadus morhua) from Coastal Newfoundland

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