Artificial reefs are used to enhance populations of marine organisms, but relatively few studies have quantitatively evaluated which attributes of reef structure are most critical in determining whether assemblages of organisms on artificial reefs are similar to those on natural reefs. Using five pairs of artificial and natural reefs that spanned 225 km in the Southern California...
We evaluated the influence of environmental exposure of juvenile Atlantic cod (Gadus morhua) to inform interpretations of natal origins and movement patterns using otolith geochemistry. Laboratory rearing experiments were conducted with a variety of temperature (∼5, 8.5, and 12°C) and salinity (∼25, 28.5, and 32 PSU) combinations. We measured magnesium (Mg), manganese (Mn...
Estimates of trophic levels (TLs) are used to calibrate, parameterize, and validate foodweb models and to calculate metrics and indicators of foodweb structure and human impacts. We develop a method to estimate TL from nitrogen stable isotope data (<mml:math><mml:mrow><mml:msup><mml:mrow><mml:mi>δ</mml:mi></mml:mrow><mml:mrow><mml:mn>15</mml:mn></mml:mrow></mml:msup></mml:mrow...
This study presents a state-space modelling framework for the purposes of stock assessment. The stochastic population dynamics build on the notion of correlated survival and capture events among individuals. The correlation is thought to arise as a combination of schooling behaviour, a spatially patchy environment, and common but unobserved environmental factors affecting all the...
The eastern Baltic (EB) cod (Gadus morhua) stock was depleted and overexploited for decades until the mid-2000s, when fishing mortality rapidly declined and biomass started to increase, as shown by stock assessments. These positive developments were partly assigned to effective management measures, and the EB cod was considered one of the most successful stock recoveries in...
This article summarizes some of my accomplishments during a 45-year career in fisheries science that ranged from conducting fish stock assessments, working for an international marine science organization, and managing a variety of scientific projects and activities, to finally serving as a scientific editor. In doing so, I have tried to focus on lessons learned. Starting my...
The critical depth concept was first recognized by Gran and Braarud (1935). During summer, in the Bay of Fundy, they observed an unexpected no bloom situation. Their interpretation was that high amounts of detritus of terrestrial origin caused too murky water and insufficient light for the tidally mixed phytoplankton. Almost 20 years later, this was elaborated by Sverdrup (1953...
The annual phytoplankton bloom is a key event in pelagic ecosystems. Variability in the timing, or phenology, of these blooms affects ecosystem dynamics with implications for carbon export efficiency and food availability for higher trophic levels. Furthermore, interannual variability in phytoplankton bloom timing may be used to monitor changes in the pelagic ecosystem that are...
In this study, we document the regional variations of bloom phenology in the Southern Ocean, based on a 13-year product of ocean colour measurements co-located with observation-based estimates of the mixed-layer depth. One key aspect of our work is to discriminate between mixed-layer integrated blooms and surface blooms. By segregating blooms that occur before or after the winter...
The critical depth hypothesis (CDH) is a predictive criteria for the onset of phytoplankton blooms that comes from the steady-state analytical solution of a simple mathematical model for phytoplankton growth presented by Sverdrup in 1953. Sverdrup's phytoplankton-only model is very elementary compared with state-of-the-art ecosystem models whose numerical solution in a time...
About 60 years ago, the critical depth hypothesis was proposed to describe the occurrence of spring phytoplankton blooms and emphasized the role of stratification for the timing of onset. Since then, several alternative hypotheses appeared focusing on the role of grazing and mixing processes such as turbulent convection or wind activity. Surprisingly, the role of community...
Sverdrup (1953. On conditions for the vernal blooming of phytoplankton. Journal du Conseil International pour l'Exploration de la Mer, 18: 287–295) was quite careful in formulating his critical depth hypothesis, specifying a “thoroughly mixed top layer” with mixing “strong enough to distribute the plankton organisms evenly through the layer”. With a few notable exceptions, most...
Published more than 60 years ago in this Journal, the article in which Sverdrup proposed the concept of critical depth to explain the initiation of the spring bloom in the North Atlantic has accrued an exceptionally large number of citations and continues to be cited more than 50 times per year. The framework provided by Sverdrup has now been applied, adapted, and tested across...
Denmark was the first nation in Europe to promote the use of Fully Documented Fisheries (FDF) through Remote Electronic Monitoring (REM) and CCTV camera systems, with pilot schemes in place since 2008. In theory, such a scheme could supplement and even potentially replace expensive control and monitoring programmes; and when associated with a catch quota management (CQM) system...
Conservation concerns and new management policies such as the implementation of ecosystem-based approaches to fisheries management are motivating an increasing need for estimates of mortality associated with commercial fishery discards and released fish from recreational fisheries. Traditional containment studies and emerging techniques using electronic tags on fish released to...
For EU member states to meet the requirements of the Marine Strategy Framework Directive and the reformed Common Fisheries Policy, it will be necessary to improve data collection related to many fisheries that are at present subject to relatively little monitoring or scientific research. This study evaluated the use of on-board camera systems to collect data from Cancer pagurus...
Regulations on the exploitation of populations of commercially important fish species and the ensuing consumer interest in sustainable products have increased the need to accurately identify the population of origin of fish and fish products. Although genomics-based tools have proven highly useful, there are relatively few examples in marine fish displaying accurate origin...
There are currently no dedicated recruitment survey data available in support of the assessment of the abundance and distribution of Northeast Atlantic (NEA) mackerel (Scomber scombrus), one of the most widespread and commercially important fish stocks in the North Atlantic. This is despite the fact that an estimate of recruitment is an important requirement for the provision of...
Exploited fish populations frequently exhibit truncated age-structure. To address a basic question in fisheries science and conservation biology—how does age truncation affect population dynamics and productivity?—we explored the effect of age-structure on recruitment dynamics of ten stocks of Atlantic cod (Gadus morhua). Based on six alternative stock–recruitment relationships...
Selectivity has traditionally been well estimated internally in stock assessment models when length or age composition data are available. However, in stock assessment, temporal or spatial variation in fishery or stock structure can lead to misspecification of the selectivity pattern, which can contribute substantially to the uncertainty in stock assessment results. Consequently...
The tropical spiny lobster, Panulirus ornatus, is farmed in floating sea cages situated in shallow coastal waters in many parts of the Asia-Pacific region. Despite the rapid expansion of this aquaculture activity, very little is known about its environmental impacts. This study combines computer modelling with previous laboratory measures to provide information on benthic carbon...
The legal minimum length (LML) of female Southern Rock Lobster (Jasus edwardsii) was reduced in the Tasmanian fishery in 1966 for higher sustainable catches. Originally, the LML was to be reduced in slow growth southern areas only; however, the change was implemented across the entire fishery due to lobbying by commercial fishers. The lower LML has been controversial ever since...
A long-term tagging dataset on southern rock lobster (Jasus edwardsii) conducted at the Crayfish Point Scientific Reserve near Hobart, Tasmania, Australia, was used to determine how survey number and survey duration affected the precision of survival estimates of male and female lobsters to ensure sustainable exploitation of the population. Tagging surveys were undertaken twice...
In Belize, beginning in 2011 at Glover's Reef Marine Reserve, and in 2012 at Port Honduras Marine Reserve, fishers have been required to keep logbooks to document their catch and effort. A Bayesian depletion model including in-season recruitment was applied to the standardized catch per unit effort (cpue) of Caribbean spiny lobster (Panulirus argus) from the logbooks to estimate...
Variability in the fluctuations of two Scottish lobster populations, the Hebrides and Southeast, was investigated from available long dataseries of fishery and environmental variables. In a multivariate context, relationships between selected environmental variables and the fishery data were studied at different spatial and temporal (annual, spring, and autumn) scales and from...