Effects of fishing during the spawning period: implications for sustainable management
Overzee, H.M.J. van; Rijnsdorp, A.D. - \ 2015
Reviews in Fish Biology and Fisheries 25 (2015)1. - ISSN 0960-3166 - p. 65 - 83.
cod gadus-morhua - loligo-vulgaris-reynaudii - north-sea plaice - halibut hippoglossus-stenolepis - palinurus-elephas fabricius - pleuronectes-platessa l - life-history evolution - coral-reef fish - atlantic cod - closed areas
While fishery closures during the spawning season are commonplace, direct evidence for their benefit is mainly restricted to species forming large spawning aggregations. This paper analyses the conditions under which spawning closures could contribute to sustainable fisheries management by reviewing how fishing during spawning may affect the physiology, behaviour and ecology of individuals and how this may influence the dynamics and the genetics of the population. We distinguish between the effects of fishing activities in relation to mortality, disturbance of spawning activity, and impact on spawning habitat. Spawning closures may be of benefit it they: (1) reduce the fishing mortality of the large and older spawners; (2) avoid negative effects on spawning habitats; (3) reduce the risk of over-exploitation in species which form large spawning aggregations; (4) reduce the evolutionary effects on maturation and reproductive investment; and (5) reduce the risk of over-exploitation of specific spawning components. The contribution of spawning closures to sustainable fisheries will differ among species and depends on the complexity of the spawning system, the level of aggregation during spawning and the vulnerability of the spawning habitat. The importance of these closures depends on the degree of population depletion but does not cease when populations are ‘healthy’ (i.e. no sign that recruitment is impaired).
Evolutionary impact assessment: accounting for evolutionary consequences of fishing in an ecosystem approach to fisheries management
Laugen, A.T. ; Engelhard, G.H. ; Whitlock, R. ; Mollet, F.M. ; Rijnsdorp, A.D. - \ 2014
Fish and Fisheries 15 (2014)1. - ISSN 1467-2960 - p. 65 - 96.
cod gadus-morhua - maturation reaction norms - effective population-size - life-history evolution - north-sea plaice - pike esox-lucius - herring clupea-harengus - eco-genetic model - atlantic cod - marine fish
Managing fisheries resources to maintain healthy ecosystems is one of the main goals of the ecosystem approach to fisheries (EAF). While a number of international treaties call for the implementation of EAF, there are still gaps in the underlying methodology. One aspect that has received substantial scientific attention recently is fisheries-induced evolution (FIE). Increasing evidence indicates that intensive fishing has the potential to exert strong directional selection on life-history traits, behaviour, physiology, and morphology of exploited fish. Of particular concern is that reversing evolutionary responses to fishing can be much more difficult than reversing demographic or phenotypically plastic responses. Furthermore, like climate change, multiple agents cause FIE, with effects accumulating over time. Consequently, FIE may alter the utility derived from fish stocks, which in turn can modify the monetary value living aquatic resources provide to society. Quantifying and predicting the evolutionary effects of fishing is therefore important for both ecological and economic reasons. An important reason this is not happening is the lack of an appropriate assessment framework. We therefore describe the evolutionary impact assessment (EvoIA) as a structured approach for assessing the evolutionary consequences of fishing and evaluating the predicted evolutionary outcomes of alternative management options. EvoIA can contribute to EAF by clarifying how evolution may alter stock properties and ecological relations, support the precautionary approach to fisheries management by addressing a previously overlooked source of uncertainty and risk, and thus contribute to sustainable fisheries.
Is age structure a relevant criterion for the health of fish stocks?
Brunel, T.P.A. ; Piet, G.J. - \ 2013
ICES Journal of Marine Science 70 (2013)2. - ISSN 1054-3139 - p. 270 - 283.
cod gadus-morhua - northern north-sea - atlantic cod - spawning stock - fisheries sustainability - reference points - climate-change - baltic cod - egg size - recruitment
The age and size structure of exploited fish stocks is one of the criteria for Good Environmental Status of commercial fish. However, two underlying assumptions to this criterion remain to be tested: first, that a well-balanced age structure is indeed indicative of a “healthier” stock, and second, that managers can exert a control on the age structure, independently from the regulation of stock abundance. This study investigates these questions using simulations from a population model in which recruitment is based on egg production, which is more sensitive to age structure variations than the traditionally used spawning stock biomass (SSB) and that was parameterized to represent the population dynamics of North Sea cod, plaice, and herring. Our results show that (i) the age structure is highly dependent on the selection pattern, as well as on the level of fishing mortality; (ii) the selection pattern determines the ability of fish stocks to withstand, and recover from, external perturbation; and (iii) the selection pattern determines the output of the fishery providing the management option to balance stable but relatively low yields vs strongly fluctuating high yields. Therefore, we propose to make the selection pattern, for which clear management targets can be set, a policy goal instead of the age structure that is currently in place
Can fisheries-induced evolution shift reference points for fisheries management?
Heino, M. ; Baulier, L. ; Boukal, D.S. ; Mollet, F.M. ; Rijnsdorp, A.D. - \ 2013
ICES Journal of Marine Science 70 (2013)4. - ISSN 1054-3139 - p. 707 - 721.
cod gadus-morhua - north-sea plaice - life-history evolution - exploited fish stocks - pleuronectes-platessa l - eco-genetic model - atlantic cod - population-dynamics - reproductive investment - natural mortality
Biological reference points are important tools for fisheries management. Reference points are not static, but may change when a population's environment or the population itself changes. Fisheries-induced evolution is one mechanism that can alter population characteristics, leading to “shifting” reference points by modifying the underlying biological processes or by changing the perception of a fishery system. The former causes changes in “true” reference points, whereas the latter is caused by changes in the yardsticks used to quantify a system's status. Unaccounted shifts of either kind imply that reference points gradually lose their intended meaning. This can lead to increased precaution, which is safe, but potentially costly. Shifts can also occur in more perilous directions, such that actual risks are greater than anticipated. Our qualitative analysis suggests that all commonly used reference points are susceptible to shifting through fisheries-induced evolution, including the limit and “precautionary” reference points for spawning-stock biomass, Blim and Bpa, and the target reference point for fishing mortality, F0.1. Our findings call for increased awareness of fisheries-induced changes and highlight the value of always basing reference points on adequately updated information, to capture all changes in the biological processes that drive fish population dynamics.
Assessing effectiveness of electrical stunning and chillingin ice water of farmed yellowtail kingfish, common sole and pike-perch
Llonch, P. ; Lambooij, E. ; Reimert, H.G.M. ; Vis, J.W. van de - \ 2012
Aquaculture 364-365 (2012). - ISSN 0044-8486 - p. 143 - 149.
catfish clarias-gariepinus - atlantic cod - fresh-water - fish - temperature - quality - stress - brain - l.
Animals should be rendered unconscious before slaughter in order to avoid suffering or pain. The objective of this study was to evaluate an electrical stunning after dewatering to induce instantaneous unconsciousness and insensibility in yellowtail kingfish (Seriola lalandi), common sole (Solea solea) and pike-perch (Stizostedion lucioperca). To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 10 min. Loss of consciousness and sensibility were assessed by neural (EEG), physiological (ECG) and behavioural parameters. An epileptiform insult was observed in all yellowtail kingfish (n = 27), common sole (n = 25) and pike-perch (n = 25) after administering a current of 0.54 +/- 0.12 A(rms) (124 V dc and 11 V-rms ac; 100 Hz), 0.65 +/- 0.23 A(rms) (98 V dc and 8.4 V-rms ac; 100 Hz) and 0.75 +/- 0.24 A(rms) (144 V dc and 13 V-rms ac; 100 Hz) during 1 s through the head of individual fish, respectively. When yellowtail kingfish (n = 11) was submitted to a 5 s electrical stun followed by chilling in ice water, this resulted in passing 0.72 +/- 0.13 A(rms) for 5 s and no recovery during chilling. In the case of common sole (n = 10) and pike-perch (n = 12), passing 1.4 +/- 0.64 and 0.75 +/- 0.24 A(rms) during 5 s followed by chilling in ice water for 10 min resulted in an irrecoverable stun in 9 out 10 fish and 11 out 12 fish, respectively. We conclude that for yellowtail kingfish the investigated combination of electrical stunning and chilling is suitable for humane slaughter, whereas for common sole and pike-perch this procedure needs to be optimised. (C) 2012 Elsevier B.V. All rights reserved.
Conservation physiology of marine fishes: advancing the predictive capacity of models
Jorgensen, C. ; Peck, M.A. ; Antognarelli, F. ; Teal, L.R. - \ 2012
Biology Letters 8 (2012)8. - ISSN 1744-9561 - p. 900 - 903.
climate-change - metabolic scope - gadus-morhua - atlantic cod - body-mass - temperature - ocean
At the end of May, 17 scientists involved in an EU COST Action on Conservation Physiology of Marine Fishes met in Oristano, Sardinia, to discuss how physiology can be better used in modelling tools to aid in management of marine ecosystems. Current modelling approaches incorporate physiology to different extents, ranging from no explicit consideration to detailed physiological mechanisms, and across scales from a single fish to global fishery resources. Biologists from different sub-disciplines are collaborating to rise to the challenge of projecting future changes in distribution and productivity, assessing risks for local populations, or predicting and mitigating the spread of invasive species.
The effect of temperature and pH on the growth and physiological response of juvenile yellowtail kingfish Seriola lalandi in recirculating aquaculture systems
Abbink, W. ; Blanco Garcia, A. ; Roques, J.A.C. ; Partridge, G. ; Kloet, K. ; Schneider, O. - \ 2012
Aquaculture 330-333 (2012). - ISSN 0044-8486 - p. 130 - 135.
acid-base-balance - cod gadus-morhua - stress-response - atlantic cod - fish size - environmental hypercapnia - dicentrarchus-labrax - feed conversion - cold-water - sea bass
A search for a viable new fish species for culture in recirculating aquaculture systems (RAS) in the Netherlands identified yellowtail kingfish Seriola lalandi as having excellent potential. To assist in determining the most appropriate water quality conditions for this species in RAS, the effect of water temperature (21, 23.5, 25, 26.5 and 29 °C) and pH (6.58, 7.16 and 7.85) was tested in two separate experiments. Growth performance, feed conversion, stress-physiological and metabolic parameters were assessed in juvenile yellowtail kingfish grown in pilot-scale RAS. Growth was optimised at a water temperature of 26.5 °C, in combination with maximum food intake and optimum food conversion ratio (FCR). Increasing temperature from 21 °C to 26.5 °C resulted in a 54% increase in the fish's final weight after 30 days. A water pH of 6.58 resulted in mortality and inhibited both growth and FCR due to physiological disruptions to which the fish could not adapt
Evaluating the suitability of coupled biophysical models for fishery management
Hinrichsen, H.H. ; Dickey-Collas, M. ; Huret, M. ; Peck, M.A. - \ 2011
ICES Journal of Marine Science 68 (2011)7. - ISSN 1054-3139 - p. 1478 - 1487.
cod gadus-morhua - arcto-norwegian cod - sprat sprattus-sprattus - marine protected areas - early-life stages - north-sea - atlantic cod - environmental variability - pelagic juveniles - climate-change
The potential role of coupled biophysical models in enhancing the conservation, management, and recovery of fish stocks is assessed, with emphasis on anchovy, cod, herring, and sprat in European waters. The assessment indicates that coupled biophysical models are currently capable of simulating transport patterns, along with temperature and prey fields within marine ecosystems; they therefore provide insight into the variability of early-life-stage dynamics and connectivity within stocks. Moreover, the influence of environmental variability on potential recruitment success may be discerned from model hindcasts. Based on case studies, biophysical modelling results are shown to be capable of shedding light on whether stock management frameworks need re-evaluation. Hence, key modelling products were identified that will contribute to the development of viable stock recovery plans and management strategies. The study also suggests that approaches combining observation, process knowledge, and numerical modelling could be a promising way forward in understanding and simulating the dynamics of marine fish populations
Implications of fisheries-induced changes in stock structure and reproductive potential for stock recovery of a sex-dimorphic species, North Sea plaice
Rijnsdorp, A.D. ; Damme, C.J.G. van; Witthames, P.R. - \ 2010
ICES Journal of Marine Science 67 (2010). - ISSN 1054-3139 - p. 1931 - 1938.
cod gadus-morhua - pleuronectes-platessa l - maturation reaction norms - annual egg-production - atlantic cod - broadcast spawner - fecundity - growth - size - age
A key assumption in stock assessment and stock forecasts often is that spawning-stock biomass (SSB) and egg production are proportional and that the reproductive potential is independent of stock structure (age composition and sex ratio). Based on a 60-year time-series of total egg production (TEP) of North Sea plaice, we demonstrate that this assumption could result in a biased perception of the temporal trend in reproductive potential. The time-series incorporates: (i) annual observations on maturity, growth, and condition, (ii) a predictive model for interannual variations in fecundity caused by variations in body condition and by the probability of being a recruit spawner, and (iii) a cohort analysis of sex-specific landings-at-age since 1948. Following an increase in fishing mortality rate, TEP declined by a factor of 7–8 from a peak in the 1970s to a minimum in 1999–2000. Concurrent with this decline, the contribution of recruit spawners and the size difference between spawning males and females decreased. The implications of phenotypic plasticity and fisheries-induced evolutionary changes in growth and maturation for the recovery potential of the plaice stock are discussed.
Effects of chronic and periodic exposure to ammonia on growth and blood physiology in juvenile turbot (Scophthalmus maximus)
Foss, A. ; Imsland, A.K. ; Roth, B. ; Schram, E. ; Stefansson, S.O. - \ 2009
Aquaculture 296 (2009)1-2. - ISSN 0044-8486 - p. 45 - 50.
bass dicentrarchus-labrax - food utilization - nitrogen-excretion - external ammonia - chronic toxicity - atlantic cod - marine fish - water - trout - plasma
Juvenile turbot (Scophthalmus maximus) were exposed periodically and chronically to different levels of un-ionised ammonia (UIA-N) and the subsequent effect on growth and food conversion efficiency was studied. Fish with a mean (SD) initial weight 19.3 (3.9) g, were exposed to five treatments consisting of a control group, two groups (ChronicLow and ChronicHigh, UIA-N levels of 0.13 and 0.25 mg l- 1, respectively) chronically exposed to ammonia and two groups (LowPulse and HighPulse) exposed to the same levels as above for a short period daily. The fish were held for 64 days at 18 °C, a pH of 8.04 and a salinity of 33.5‰. At the end of the experiment, fish from the Control group had a significantly higher mean weight (95.5 g) compared to all other groups. Fish from the ChronicHigh group displayed the lowest mean weight (74.6 g), whereas fish in the ChronicLow, LowPulse and HighPulse groups displayed mean weights of: 79.3 g, 82.8 g and 81.9 g, respectively. Blood ion concentrations were not affected significantly in any of the treatments, whereas minor reductions in blood pH, partial pressure of CO2 and total CO2 content were found in ammonia exposed groups up until day 44 of the experiment. Feed conversion efficiency, daily feeding rate and total feed consumption did not vary significantly between treatments. The study demonstrate that short daily ammonia peaks may result in negative effects on growth, equivalent to that found under chronic ammonia exposure in juvenile turbot.
Regime shifts in marine ecosystems: detection, prediction and management
Deyoung, B. ; Barange, M. ; Beaugrand, G. ; Harris, R. ; Perry, R.I. ; Scheffer, M. ; Werner, F. - \ 2008
Trends in Ecology and Evolution 23 (2008)7. - ISSN 0169-5347 - p. 402 - 409.
long-term changes - cod gadus-morhua - north pacific - climate variability - coral-reef - fishery management - german bight - atlantic cod - ocean - sea
Regime shifts are abrupt changes between contrasting, persistent states of any complex system. The potential for their prediction in the ocean and possible management depends upon the characteristics of the regime shifts: their drivers (from anthropogenic to natural), scale (from the local to the basin) and potential for management action (from adaptation to mitigation). We present a conceptual framework that will enhance our ability to detect, predict and manage regime shifts in the ocean, illustrating our approach with three well-documented examples: the North Pacific, the North Sea and Caribbean coral reefs. We conclude that the ability to adapt to, or manage, regime shifts depends upon their uniqueness, our understanding of their causes and linkages among ecosystem components and our observational capabilities.
Diet overlap and prey selection through metamorphosis in Irish Sea cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus)
Rowlands, W.L. ; Dickey-Collas, M. ; Geffen, A.J. ; Nash, R.D.M. - \ 2008
Canadian Journal of Fisheries and Aquatic Sciences 65 (2008)7. - ISSN 0706-652X - p. 1297 - 1306.
calanus-finmarchicus gunnerus - northern north-sea - fish larvae - helgolandicus claus - gadoid larvae - niche breadth - atlantic cod - early-life - food - size
Copepods in the genus Calanus are usually considered to be the preferred prey of gadoid larvae in many areas; however, in the Irish Sea, the abundances of these Calanus species are low and highly variable. We use this situation to test whether Calanus species are still actively selected by gadoid larvae in Calanus-poor environments. Diets of Irish Sea cod (Gadus morhua), haddock (Melanogrammus aeglefinus), and whiting (Merlangius merlangus) were studied from the yolk-sac stage to the juvenile stage. Prey from stomach contents were compared with in situ abundance via an index of prey preference. As expected, all larvae selected copepod nauplii at the onset of feeding. As the larvae developed, their prey preferences changed and varied with species. Cod and whiting showed a similar transition of prey species preference, with a clear preference for Calanus species after metamorphosis, even in this area of low abundance of these Calanus species. The diet composition of haddock differed from that of cod and whiting, as nauplii remained in their diet later into development and there was little preference for individual copepod species detected. The differences in prey selectivity suggested between these gadoids may be attributed to their population variability through the known variability of their preferred prey items
Population structure of the thornback ray (Raja clavata L.) in British waters
Chevolot, M. ; Ellis, J.R. ; Hoarau, G. ; Rijnsdorp, A.D. ; Stam, W.T. ; Olsen, J.L. - \ 2006
Journal of Sea Research 56 (2006)4. - ISSN 1385-1101 - p. 305 - 316.
cod gadus-morhua - pleuronectes-platessa l. - southern north-sea - gulf-of-mexico - genetic-structure - atlantic cod - multilocus genotypes - microsatellite data - geographic scales - reaction norms
Prior to the 1950s, thornback ray (Raja clavata L.) was common and widely distributed in the seas of Northwest Europe. Since then, it has decreased in abundance and geographic range due to over-fishing. The sustainability of ray populations is of concern to fisheries management because their slow growth rate, late maturity and low fecundity make them susceptible to exploitation as victims of by-catch. We investigated the population genetic structure of thornback rays from 14 locations in the southern North Sea, English Channel and Irish Sea. Adults comprised <4% of the total sampling despite heavy sampling effort over 47 hauls; thus our results apply mainly to sexually immature individuals. Using five microsatellite loci, weak but significant population differentiation was detected with a global FST = 0.013 (P <0.001). Pairwise Fst was significant for 75 out of 171 comparisons. Although earlier tagging studies suggest restricted foraging distances from home areas, the absence of genetic differentiation between some distant populations suggests that a substantial fraction of individuals migrate over wide areas. Autumn/winter locations appear to have a lower level of differentiation than spring/summer, which could be due to seasonal migration. Management and conservation of thornback ray populations will be challenging as population structure appears to be dynamic in space and time
Improving the definition of fishing effort for important European fleets by accounting for the skipper effect
Marchal, P. ; Andersen, B. ; Bromley, E.H.C. ; Iriondo, A. ; Mahevas, S. ; Quirijns, F.J. ; Tien, N.S.H. - \ 2006
Canadian Journal of Fisheries and Aquatic Sciences 63 (2006)3. - ISSN 0706-652X - p. 510 - 533.
ideal free distribution - north-sea - competitive interactions - spatial-distribution - catching efficiency - trawl fishery - gadus-morhua - atlantic cod - catchability - vessels
The scope of this paper is to quantify, for a wide selection of European fisheries, fishing tactics and strategies and to evaluate the benefits of adjusting the definition of. fishing effort using these elements. Fishing tactics and strategies were identified by metiers choices and a series of indices. These indices have been derived to reflect shifts in tactics (within a fishing trip) and in strategies (within a year). The Shannon-Wiener spatial diversity indices of fishing tactics (FT_SW) and strategies (YE_SW) had the greatest impact on catch rates. In particular, FT_SW was always negatively correlated to catch rates. One may anticipate that during a fishing trip, vessels with high FT_SW have been searching fish aggregations for a long time, while vessels with low FT_SW have been more efficient in finding these aggregations. The linkage between YE_SW and catch rates was of a more complex nature. Adjusting fishing effort by means of (i) the metier effect and (ii) the indices of tactics and strategies generally led to a substantial gain in the precision of the relationship between fishing mortality and fishing effort.
|Major histocompatibility lineages and immune gene function in teleost fishes: the road not taken
Stet, R.J.M. ; Kruiswijk, C.P. ; Dixon, B. - \ 2003
Critical Reviews in Immunology 23 (2003)5&6. - ISSN 1040-8401 - p. 441 - 471.
mhc class-i - trout oncorhynchus-mykiss - salmon salmo-salar - complex class-i - gadus-morhua l. - carp cyprinus-carpio - chain-encoding genes - mhccyca class-i - rainbow-trout - atlantic cod
It has become increasingly clear over the course of the past decade that the immune system genes of teleosts and tetrapods are plainly derived from common ancestral genes. The last 5 years, however, have also made it abundantly clear that in the teleost genome some of these genes are organized in a manner very different from that seen in mammals. These differences are probably the result of differences in life history traits, such as fecundancy, within each group of species when faced with an evolutionary fork in the road shortly after their divergence from each other. One group, the tetrapods, including mammals, chose a highly organized linked major histocompatibility complex, while in teleosts the major histocompatibility genes remained unlinked. In this review we will discuss the structural and functional implications of this different organization, particularly for major histocompatibility genes, but drawing on the current knowledge of some other genes for further support for the hypothesis that each group took a different road, one more traveled and one less taken.