Posts Tagged 'fish'

Evaluating present and future potential of arctic fisheries in Canada


• Climate change will increase access to Arctic marine fish stocks in Canada.

• Projections show positive increases in fisheries catch and value potential with climate change.

• Range shifts driven by ocean warming will lead to increased catch potential.

• Ocean acidification may reduce projected increase in catch potential.

• Ecological, economic, social and cultural impacts of exploitation must be considered.


The Arctic remains one of the most pristine marine regions in the world, however climate change and increasing favourable conditions is triggering increasing exploration and development of commercial fisheries. Canada’s Arctic marine capture fisheries are currently small relative to fisheries in other regions in Canada but small scale, predominantly Inuit fisheries are more wide spread. In this study, catch data was first used to estimate the current state of Arctic marine fisheries. Next, an integrated modelling approach was used to estimate the current and future fisheries potentials under high and low climate change scenarios. Comparisons of the current (2004–2015) annual reported tonnage and modelled estimates (±standard deviation) suggest that annual sustainable fisheries catch potential could be much greater at 4.07 (±2.86) million tonnes than the current catch of 189 (±6.26) thousand tonnes. Under a high climate change scenario, future (2091–2100) fisheries potential was projected to increase to 6.95 (±5.07) million tonnes of catch, while under low climate change scenario catch potential was similar to estimates of current catch potential. However, the greatest source of variance in catch potential estimates came from parameter uncertainty, followed by scenario and model uncertainty. These results contribute to understanding Canada’s Arctic marine ecosystems in the face of a rapidly changing environment, yet proper steps must be taken to ensure cultural preservation for Inuit communities as well as ecological, economic, and social sustainability.

Continue reading ‘Evaluating present and future potential of arctic fisheries in Canada’

Critically examining the knowledge base required to mechanistically project climate impacts: a case study of Europe’s fish and shellfish

An amalgam of empirical data from laboratory and field studies is needed to build robust, theoretical models of climate impacts that can provide science‐based advice for sustainable management of fish and shellfish resources. Using a semi‐systematic literature review, Gap Analysis and multilevel meta‐analysis, we assessed the status of empirical knowledge on the direct effects of climate change on 37 high‐value species targeted by European fisheries and aquaculture sectors operating in marine and freshwater regions. Knowledge on potential climate change‐related drivers (single or combined) on several responses (vital rates) across four categories (exploitation sector, region, life stage, species), was considerably unbalanced as well as biased, including a low number of studies (a) examining the interaction of abiotic factors, (b) offering opportunities to assess local adaptation, (c) targeting lower‐value species. The meta‐analysis revealed that projected warming would increase mean growth rates in fish and mollusks and significantly elevate metabolic rates in fish. Decreased levels of dissolved oxygen depressed rates of growth and metabolism across coherent species groups (e.g., small pelagics, etc.) while expected declines in pH reduced growth in most species groups and increased mortality in bivalves. The meta‐analytical results were influenced by the study design and moderators (e.g., life stage, season). Although meta‐analytic tools have become increasingly popular, when performed on the limited available data, these analyses cannot grasp relevant population effects, even in species with a long history of study. We recommend actions to overcome these shortcomings and improve mechanistic (cause‐and‐effect) projections of climate impacts on fish and shellfish.

Continue reading ‘Critically examining the knowledge base required to mechanistically project climate impacts: a case study of Europe’s fish and shellfish’

Growth of the estuarine fish Fundulus heteroclitus in response to diel-cycling hypoxia and acidification: interaction with temperature

Growth rate of Fundulus heteroclitus was examined at 25 and 30 °C in nine treatments of diel-cycling dissolved oxygen (DO) and pH. Extreme diel-cycling DO (1–11 mg O2·L−1) negatively impacted growth during 10 days at 30 °C, but not at 25 °C. Moderate DO cycles (3–9 mg O2·L−1) had no direct growth impact at either temperature. Fish did not appear to acclimate, during days 10–30, to the initial growth-limiting effects of extreme diel DO cycles at 30 °C. Diel-cycling DO interacts synergistically with temperature to impact growth. There was no evidence of an independent growth effect of either moderate pH cycles (7.2–7.8) or extreme pH cycles (6.8–8.1) at either temperature. Mean low pCO2 levels in extreme cycles were ∼32 000 and ∼47 000 μatm at 25 and 30 °C, respectively. It is noteworthy that these high mean nightly pCO2 levels are more than an order of magnitude higher than the chronic mean oceanic pCO2 of ∼1000 μatm projected by the year 2100.

Continue reading ‘Growth of the estuarine fish Fundulus heteroclitus in response to diel-cycling hypoxia and acidification: interaction with temperature’

Functional loss in herbivores drives runaway expansion of weedy algae in a near-future ocean


• Elevated CO2 and warming increased productivity of turf algae.

• Elevated CO2 increased per capita feeding rates of gastropods.

• Ocean warming reduced grazer diversity, density, and biomass.

• As a result, ocean warming drove a fourfold expansion of weedy algal species.


The ability of a community to absorb environmental change without undergoing structural modification is a hallmark of ecological resistance. The recognition that species interactions can stabilize community processes has led to the idea that the effects of climate change may be less than what most considerations currently allow. We tested whether herbivory can compensate for the expansion of weedy algae triggered by CO2 enrichment and warming. Using a six-month mesocosm experiment, we show that increasing per capita herbivory by gastropods absorbs the boosted effects of CO2 enrichment on algal production in temperate systems of weak to moderate herbivory. However, under the combined effects of acidification and warming this compensatory effect was eroded by reducing the diversity, density and biomass of herbivores. This loss of functionality combined with boosted primary productivity drove a fourfold expansion of weedy algal species. Our results demonstrate capacity to buffer ecosystems against CO2 enrichment, but loss of this capacity through ocean warming either in isolation or combined with CO2, driving significant algal turf expansion. Identifying compensatory processes and the circumstances under which they prevail could potentially help manage the impacts of ocean warming and acidification, which are further amplified by local disturbances such as habitat loss and herbivore over-exploitation.

Continue reading ‘Functional loss in herbivores drives runaway expansion of weedy algae in a near-future ocean’

Water acidification causes death of marine ornamental fish (Perciformes: Pomacentridae) during transport: contributing to the conservation of wild populations

Pomacentridae is a common family in the aquarium fish trade. Most species are harvested from nature. Here we evaluate the following water parameters in the pomacentrid sergeant major, Abudefduf saxatilis (Linnaeus, 1758), to assess their stress level during a 24, 48, and 72 hours transport: dissolved oxygen (DO), total ammonia, and pH. In addition, we evaluated the following physiological parameters: plasma osmolality, muscle water content, blood glucose, and the enzyme activities of the branchial carbonic anhydrase (CA), the hepatic glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD). The mortality of fish measuring >6 cm total length was 22%, while no mortality was observed for fish measuring <6 cm. The pH of the water was significantly correlated with fish mortality, especially for the initial 24 hours of transport. Hypoxia after 24–48 hours also led to fish mortality, but build up ammonia was not a problem even after 72 hours. We suggest that a minimum water volume of 125 ml/g fish is necessary for safe and cost-effective transport of the sergeant major, preferably with <6 cm in total length.

Continue reading ‘Water acidification causes death of marine ornamental fish (Perciformes: Pomacentridae) during transport: contributing to the conservation of wild populations’

Mass mortality of fish and water quality assessment in the tropical Adyar estuary, South India

Mass mortality of fishes was reported at the Adyar estuary, South India, during November 2017. The probable reasons for fish mortality are analyzed in this paper. Critical assessments on water quality parameters including the metal concentrations, nutrients, and histology of gills and liver of fish (Mugil cephalus) isolated from the impact zone were performed. Among the metals observed, chromium showed levels (3.64 ± 0.001 mg L−1) much above the average permissible limits (0.1 mg L−1). The measured values of physico-chemical parameters in the impact zone are as follows: dissolved oxygen 4.7 ± 0.22 mg L−1, total alkalinity 132 ± 4 CaCO3 mg L−1, salinity 5.3 ± 0.3 PSU, temperature 27.8 ± 0.16 °C, nitrate, 1.66 ± 0.48 mg L−1, nitrite 0.01 ± 0.0008 mg L−1, ammonia 0.03 ± 0.001 mg L−1, phosphate 1.52 ± 0.002 mg L−1, and silicate 13.85 ± 3.1 mg L−1. The low salinity could have escalated the toxicity of the metal. In addition, histology of gills and liver showed cellular necrosis, epithelial lifting, hyperplasia, edema, mucous cell proliferation in the gills, cytoplasmic vacuolation of hepatocytes, and degeneration of liver which reveal that chromium toxicity is the most probable cause for mass mortality.

Raja U. K. U., Ebenezer V., Kumar A., Sanjeevi P. & Murugesan M., 2019. Mass mortality of fish and water quality assessment in the tropical Adyar estuary, South India. Environmental Monitoring and Assessment 191: 512. doi: 10.1007/s10661-019-7636-4. Article (subscription required).

Effects of elevated carbon dioxide on marine ecosystem and associated fishes

Carbon dioxide (CO2) concentrations at the ocean surface are in approximate equilibrium with the atmosphere. Consequently, the amount of CO2 dissolved in oceans increases with increasing atmospheric CO2 concentrations. Through ocean acidification, increase uptake of CO2 at the ocean surface lowers the ocean pH level. The availability of dissolved carbonate and bicarbonate primarily caused by CO2 uptake from the atmosphere also changes. Periodically or permanently elevated CO2 concentrations can become a general stress factor in aquatic environments. Excess CO2 can affect the surrounding ocean life, i.e., disturbing growth performance, reproduction, changes in skeletal and otolith development, and fish behavior. Studies on the effects of ocean acidification on fish species have recently received attention. This condition can lead to severe problems if atmospheric CO2 concentrations continue to rise. Therefore, management intervention and decisive action on excessive CO2 emission are necessary to overcome this situation. The information discussed in this review can be utilized as reference in understanding the effects of ocean acidification on marine ecosystem and associated fishes.

Continue reading ‘Effects of elevated carbon dioxide on marine ecosystem and associated fishes’

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Ocean acidification in the IPCC AR5 WG II

OUP book