How well do connectivity tools agree over the full life cycle? A case study of Irish Sea plaice Pleuronectes platessa Linnaeus, 1758.

Adult plaice in the Irish Sea have distinct traits that reflect the spawning locations that could suggest a number of different populations. However, do connectivity pathways support this concept? Different tools are directed at measuring exchange or connectivity between different life-history stages, and the challenge is to integrate the signals to obtain full life-cycle estimates. Collectively, the different methods reveal stable connectivity between known spawning and nursery grounds, with sufficient exchange to maintain a single population with weak genetic structure.

Sea anemone-anemonefish symbiosis: Behavior and mucous protein profiling.

Fish species of the genus Amphiprion (Perciformes: Pomacentridae) seek protection from predators among the tentacles of sea anemones as their natural habitat, where they live essentially unharmed from stinging by the host's nematocysts. The skin mucus of these anemonefish has been suggested as a protective mechanism that prevents the discharge of the nematocysts upon contact. Whereas some anemonefish species seem to produce their own protective mucous coating, others may acquire mucus (or biomolecules within) from the sea anemone during an acclimation period.

Growth portfolios buffer climate-linked environmental change in marine systems.

Large-scale, climate-induced synchrony in the productivity of fish populations is becoming more pronounced in the world's oceans. As synchrony increases, a population's "portfolio" of responses can be diminished, in turn reducing its resilience to strong perturbation. Here we argue that the costs and benefits of trait synchronization, such as the expression of growth rate, are context dependent.

Otolith "spawning zones" across multiple Atlantic cod populations: Do they accurately record maturity and spawning?

Specific changes identified in the otolith macrostructure of Northeast Arctic cod as "spawning zones" are presumed to represent spawning events, but recent experimental studies have challenged this relationship. Because these zones are not routinely recorded outside of Norway, otoliths from multiple Atlantic cod populations with different life history and environmental traits were first examined to see if spawning zones could be identified as a general characteristic of cod. Then, a large archival collection of cod otoliths was used to investigate temporal changes in the occurrence of spawning zones and test for correlations between maturity at age derived from otolith spawning zones and gonad maturity stages.

Differences in metabolic rate between two Atlantic cod (Gadus morhua) populations estimated with carbon isotopic composition in otoliths.

The isotopic composition of inorganic carbon in otoliths (δ13Coto) can be a useful tracer of metabolic rates and a method to study ecophysiology in wild fish. We evaluated environmental and physiological sources of δ13Coto variation in Icelandic and Northeast Arctic (NEA) cod (Gadus morhua) over the years 1914-2013. Individual annual growth increments of otoliths formed at age 3 and 8 were micromilled and measured by isotope-ratio mass spectrometry.

Lemon sole Microstomus kitt in the northern North Sea: a multidisciplinary approach to the early life-history dynamics.

Lemon sole Microstomus kitt is a commercially valuable flatfish species that occurs in shelf waters around the northeast Atlantic. Only the most basic life-history information is available for the North Sea. Spawning is generally assumed to occur between early May and October, with a peak between May and August.

Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature.

Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908-2014).

A century of fish growth in relation to climate change, population dynamics and exploitation.

Marine ecosystems, particularly in high-latitude regions such as the Arctic, have been significantly affected by human activities and contributions to climate change. Evaluating how fish populations responded to past changes in their environment is helpful for evaluating their future patterns, but is often hindered by the lack of long-term biological data available. Using otolith increments of Northeast Arctic cod (Gadus morhua) as a proxy for individual growth, we developed a century-scale biochronology (1924-2014) based on the measurements of 3,894 fish, which revealed significant variations in cod growth over the last 91 years.

Host choice and fitness of anemonefish Amphiprion ocellaris (Perciformes: Pomacentridae) living with host anemones (Anthozoa: Actiniaria) in captive conditions.

In this study, we investigated the host choice of naïve Amphiprion ocellaris, a specialist, at two different stages of development (newly settling juveniles and post-settlement juveniles). The fish were exposed to their natural and unnatural host species in the laboratory and their fitness was assessed in terms of activity and growth rate. Newly settling juveniles exhibited little host preference, while post-settlement juveniles immediately associated with their most common host in the wild.

Organ damage in Atlantic herring larvae as a result of ocean acidification.

The dissolution of anthropogenically emitted excess carbon dioxide lowers the pH of the world's ocean water. The larvae of mass spawning marine fishes may be particularly vulnerable to such ocean acidification (OA), yet the generality of earlier results is unclear. Here we show the detrimental effects of OA on the development of a commercially important fish species, the Atlantic herring (Clupea harengus).

The proteome of Atlantic herring (Clupea harengus L.) larvae is resistant to elevated pCO2.

Elevated anthropogenic pCO2 can delay growth and impair otolith structure and function in the larvae of some fishes. These effects may concurrently alter the larva's proteome expression pattern. To test this hypothesis, Atlantic herring larvae were exposed to ambient (370 μatm) and elevated (1800 μatm) pCO2 for one-month.

Outlier SNP markers reveal fine-scale genetic structuring across European hake populations (Merluccius merluccius).

Shallow population structure is generally reported for most marine fish and explained as a consequence of high dispersal, connectivity and large population size. Targeted gene analyses and more recently genome-wide studies have challenged such view, suggesting that adaptive divergence might occur even when neutral markers provide genetic homogeneity across populations. Here, 381 SNPs located in transcribed regions were used to assess large- and fine-scale population structure in the European hake (Merluccius merluccius), a widely distributed demersal species of high priority for the European fishery.

A genomic island linked to ecotype divergence in Atlantic cod.

The genomic architecture underlying ecological divergence and ecological speciation with gene flow is still largely unknown for most organisms. One central question is whether divergence is genome-wide or localized in 'genomic mosaics' during early stages when gene flow is still pronounced. Empirical work has so far been limited, and the relative impacts of gene flow and natural selection on genomic patterns have not been fully explored.

Gene-associated markers provide tools for tackling illegal fishing and false eco-certification.

Illegal, Unreported and Unregulated fishing has had a major role in the overexploitation of global fish populations. In response, international regulations have been imposed and many fisheries have been 'eco-certified' by consumer organizations, but methods for independent control of catch certificates and eco-labels are urgently needed. Here we show that, by using gene-associated single nucleotide polymorphisms, individual marine fish can be assigned back to population of origin with unprecedented high levels of precision.

Frequent skipped spawning in the world's largest cod population.

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 Northeast Arctic cod (NEAC) in a massive field and laboratory effort from 2006 to 2008.

Low-dose exposure to alkylphenols adversely affects the sexual development of Atlantic cod (Gadus morhua): acceleration of the onset of puberty and delayed seasonal gonad development in mature female cod.

Produced water (PW), a by-product of the oil-production process, contains large amount of alkylphenols (APs) and other harmful oil compounds. In the last 20 years, there have been increasing concerns regarding the environmental impact of large increases in the amounts of PW released into the North Sea. We have previously shown that low levels of APs can induce disruption of the endocrine and reproductive systems of Atlantic cod (Gadus morhua).

Analysis of the soluble matrix of vaterite otoliths of juvenile herring (Clupea harengus): do crystalline otoliths have less protein?

Otoliths are calcium carbonate concretions laid down in the inner ear of fish and used in fish age estimation. Otoliths precipitate in the form of aragonite but aberrant precipitation may result in vaterite formation instead of aragonite. Vaterite otoliths are more translucent than aragonite.