Nature recently shared a list of the most-cited papers of all time in any scientific field. That got me thinking: what are the most-cited papers in my field? And do they have any traits in common?
Me at the New England Aquarium
Methods: Simple! I performed a Web of Science database search for “shark,” and sorted results by “Citations: Highest to Lowest.” I then manually confirmed whether or not a paper counts, which I defined as “focused primarily on sharks,” rather than, say, an ecosystem wide study that mentions but clearly does not focus on sharks.
For example, a 2003 paper in PNAS entitled “Interferon-inducible gene expression signature in peripheral blood cells of patients with severe lupus” has a coauthor whose last name is shark, which obviously does not count. Another 2003 paper from the British Medical Bulletin entitled “Hazards of heavy metal contamination” also does not count, because it mentions sharks only briefly as one of many possible sources of heavy metal exposure in humans. Shark Bay, Australia, is the site of a lot of fascinating shark research, but it’s also studied for it’s biogeochemistry, and I didn’t count any of that despite the name of the location. Though borderline, I did not count a 2005 papers with 3,207 citations in Philosophical Transactions of the Royal Society B entitled “DNA barcoding Australia’s fish species,” because it did include sharks but they were not the focus (out of 207 studied species, 61 were sharks and rays). Other papers that I did not count, and a brief explanation of why I did not count them, are found at the bottom of this article.
Without further delay, the top ten most-cited papers in shark science are
- Dulvy, N. K., et al (2014). Extinction risk and conservation of the world’s sharks and rays. elife, 3, e00590. 1,532 citations READ IT HERE:
Abstract: The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes—sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world’s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery. - Stevens, J. D., Bonfil, R., Dulvy, N. K., & Walker, P. A. (2000). The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. ICES Journal of Marine Science, 57(3), 476-494. 1,309 citations. READ IT HERE.
ABSTRACT: The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated from large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. - Cortes, E. (1997). A critical review of methods of studying fish feeding based on analysis of stomach contents: application to elasmobranch fishes. Canadian journal of fisheries and aquatic sciences, 54(3), 726-738. 1,019 citations READ IT HERE
ABSTRACT: Using real data sets of elasmobranch fishes as examples, this paper presents a critical review of selected methods and statistical approaches used in fish feeding studies and makes recommendations on the application of such methodology. The percent index of relative importance is proposed as a standardized measure in dietary analyses, and a three-dimensional graphical representation of the diet is introduced. Multiway contingency table (log-linear) analysis is recommended to test for dietary variations. Caution is advised when using rank correlation to study dietary overlap and parametric tests when stomach content data do not satisfy parametric assumptions. Sampling gear type, experimental design, and statistical tests can affect results on diel feeding chronology, and stomach content weights do not suffice to interpret diel feeding chronology. On the basis of sampling requirements and model assumptions, the Diana and Olson-Mullen methods appear to be the most appropriate approaches for estimating daily ration in sharks. Use of resampling techniques is highly desirable because they provide a measure of the error in daily ration estimates. Using several criteria to evaluate the best-fitting model of gastric evacuation in fishes is also strongly advocated. Overall, increased consolidation of methods and analyses is recommended to facilitate comparative studies. - Myers, R. A., Baum, J. K., Shepherd, T. D., Powers, S. P., & Peterson, C. H. (2007). Cascading effects of the loss of apex predatory sharks from a coastal ocean. Science, 315(5820), 1846-1850. 988 citations. READ IT HERE.
ABSTRACT: Impacts of chronic overfishing are evident in population depletions worldwide, yet indirect ecosystem effects induced by predator removal from oceanic food webs remain unpredictable. As abundances of all 11 great sharks that consume other elasmobranchs (rays, skates, and small sharks) fell over the past 35 years, 12 of 14 of these prey species increased in coastal northwest Atlantic ecosystems. Effects of this community restructuring have cascaded downward from the cownose ray, whose enhanced predation on its bay scallop prey was sufficient to terminate a century-long scallop fishery. Analogous top-down effects may be a predictable consequence of eliminating entire functional groups of predators. - Baum, J. K., Myers, R. A., Kehler, D. G., Worm, B., Harley, S. J., & Doherty, P. A. (2003). Collapse and conservation of shark populations in the Northwest Atlantic. Science, 299(5605), 389-392. 979 citations. READ IT HERE.
ABSTRACT: Overexploitation threatens the future of many large vertebrates. In the ocean, tunas and sea turtles are current conservation concerns because of this intense pressure. The status of most shark species, in contrast, remains uncertain. Using the largest data set in the Northwest Atlantic, we show rapid large declines in large coastal and oceanic shark populations. Scalloped hammerhead, white, and thresher sharks are each estimated to have declined by over 75% in the past 15 years. Closed-area models highlight priority areas for shark conservation, and the need to consider effort reallocation and site selection if marine reserves are to benefit multiple threatened species. - Cortés, E. (1999). Standardized diet compositions and trophic levels of sharks. ICES Journal of marine science, 56(5), 707-717. 770 citations. READ IT HERE.
ABSTRACT: Sharks are marine consumers believed to occupy top positions in marine food webs. But surprisingly, trophic level estimates for these predators are almost non-existent. With the hope of helping better define the ecological role of sharks in marine communities, this paper presents standardized diet compositions and trophic levels calculated for a suite of species. Dietary composition for each species was derived from published quantitative studies using a weighted average index that takes into account sample size in each study. The trophic level (TL) values of the 11 food types used to characterize the diet (obtained from published accounts) were then used to calculate fractional trophic levels for 149 species representing eight orders and 23 families. Sharks as a group are tertiary consumers (TL>4), and significant differences were found among the six orders compared, which were attributable to differences between orectolobiforms (TL<4) and all other orders, and between hexanchiforms and both carcharhiniforms and squatiniforms. Among four families of carcharhiniform sharks, carcharhinids (TL=4.1, n=39) had a significantly higher TL than triakids (TL=3.8, n=19) and scyliorhinids (TL=3.9, n=21), but not sphyrnids (TL=3.9, n=6). When compared to trophic levels for other top predators of marine communities obtained from the literature, mean TL for sharks was significantly higher than for seabirds (n=28), but not for marine mammals (n=97). Trophic level and body size were positively correlated (rs=0.33), with the fit increasing (rs=0.41) when the three predominantly zooplanktivorous sharks were omitted, and especially when considering only carcharhinid sharks (rs=0.55). - Ferretti, F., Worm, B., Britten, G. L., Heithaus, M. R., & Lotze, H. K. (2010). Patterns and ecosystem consequences of shark declines in the ocean. Ecology letters, 13(8), 1055-1071. 727 citations. READ IT HERE.
Abstract: Whereas many land predators disappeared before their ecological roles were studied, the decline of marine apex predators is still unfolding. Large sharks in particular have experienced rapid declines over the last decades. In this study, we review the documented changes in exploited elasmobranch communities in coastal, demersal, and pelagic habitats, and synthesize the effects of sharks on their prey and wider communities. We show that the high natural diversity and abundance of sharks is vulnerable to even light fishing pressure. The decline of large predatory sharks reduces natural mortality in a range of prey, contributing to changes in abundance, distribution, and behaviour of small elasmobranchs, marine mammals, and sea turtles that have few other predators. Through direct predation and behavioural modifications, top-down effects of sharks have led to cascading changes in some coastal ecosystems. In demersal and pelagic communities, there is increasing evidence of mesopredator release, but cascading effects are more hypothetical. Here, fishing pressure on mesopredators may mask or even reverse some ecosystem effects. In conclusion, large sharks can exert strong top-down forces with the potential to shape marine communities over large spatial and temporal scales. Yet more empirical evidence is needed to test the generality of these effects throughout the ocean. - Baum, J. K., & Worm, B. (2009). Cascading top‐down effects of changing oceanic predator abundances. Journal of animal ecology, 78(4), 699-714. 688 citations. READ IT HERE.
ABSTRACT: Top-down control can be an important determinant of ecosystem structure and function, but in oceanic ecosystems, where cascading effects of predator depletions, recoveries, and invasions could be significant, such effects had rarely been demonstrated until recently.Here we synthesize the evidence for oceanic top-down control that has emerged over the last decade, focusing on large, high trophic-level predators inhabiting continental shelves, seas, and the open ocean.In these ecosystems, where controlled manipulations are largely infeasible, ‘pseudo-experimental’ analyses of predator–prey interactions that treat independent predator populations as ‘replicates’, and temporal or spatial contrasts in predator populations and climate as ‘treatments’, are increasingly employed to help disentangle predator effects from environmental variation and noise.Substantial reductions in marine mammals, sharks, and piscivorous fishes have led to mesopredator and invertebrate predator increases. Conversely, abundant oceanic predators have suppressed prey abundances. Predation has also inhibited recovery of depleted species, sometimes through predator–prey role reversals. Trophic cascades have been initiated by oceanic predators linking to neritic food webs, but seem inconsistent in the pelagic realm with effects often attenuating at plankton.Top-down control is not uniformly strong in the ocean, and appears contingent on the intensity and nature of perturbations to predator abundances. Predator diversity may dampen cascading effects except where nonselective fisheries deplete entire predator functional groups. In other cases, simultaneous exploitation of predator and prey can inhibit prey responses. Explicit consideration of anthropogenic modifications to oceanic foodwebs should help inform predictions about trophic control.Synthesis and applications. Oceanic top-down control can have important socio-economic, conservation, and management implications as mesopredators and invertebrates assume dominance, and recovery of overexploited predators is impaired. Continued research aimed at integrating across trophic levels is needed to understand and forecast the ecosystem effects of changing oceanic predator abundances, the relative strength of top-down and bottom-up control, and interactions with intensifying anthropogenic stressors such as climate change. - Greenberg, A. S., Avila, D., Hughes, M., Hughes, A., McKinney, E. C., & Flajnik, M. F. (1995). A new antigen receptor gene family that undergoes rearrangement and extensive somatic diversification in sharks. nature, 374(6518), 168-173. 594 citations. READ IT HERE.
ABSTRACT: IMMUNOGLOBULIN and T-cell receptor (TCR) molecules are central to the adaptive immune system. Sequence conservation, similarities in domain structure, and usage of similar recombination signal sequences and recombination machinery indicate that there was probably a time during evolution when an ancestral receptor diverged to the modern-day immunoglobulin and TCR1–3. Other molecules that undergo rearrangement have not been described in vertebrates, nor have intermediates been identified that have features of both these gene families. We report here the isolation of a new member of the immunoglobulin superfamily from the nurse shark, Ginglymostoma cirratum, which contains one variable and five constant domains and is found as a dimer in serum. Analyses of complementary DNA clones show extensive sequence diversity within variable domains, which is generated by both rearrangement and somatic diversification mechanisms. Our results suggest that rearranging loci distinct from immunoglobulin and TCR have arisen during evolution. - Heupel, M. R., Carlson, J. K., & Simpfendorfer, C. A. (2007). Shark nursery areas: concepts, definition, characterization and assumptions. Marine ecology progress series, 337, 287-297. 585 citations. READ IT HERE.
ABSTRACT: The concept of elasmobranch species using nursery areas was introduced in the early 1900s and has been an accepted aspect of shark biology and behavior for several decades. Despite several descriptions of how shark species use nursery areas and what types of regions nurseries may be found in, no explicit definition of what constitutes a shark nursery area has been presented. Here we evaluate the assumptions of the current shark nursery paradigm in light of available data. Based on examination of these assumptions and available methods of quantifying and accurately describing shark nursery areas, a new more quantitative definition of shark nursery areas is proposed. This definition requires 3 criteria to be met for an area to be identified as a nursery: (1) sharks are more commonly encountered in the area than other areas; (2) sharks have a tendency to remain or return for extended periods; and (3) the area or habitat is repeatedly used across years. These criteria make the definition of shark nursery areas more compatible with those for other aquatic species. The improved definition of this concept will provide more valuable information for fisheries managers and shark biologists.
Some overall thoughts:
A lot of these papers focus on conservation, including the negative impacts of shark population declines that are often used as an argument for conservation.
Several of them are “how to use a method” type papers, which are subsequently cited by anyone in the future who uses that method.
Several of them are reviews and synthesis, turning a vast literature into a one-stop-shop summary.
One of these papers includes more than ten coauthors, people from all over the world, showing the value of collaboration- though two are written by just one author. In both cases, the single-author paper included on this list was written by the same author.
One of these papers has been thoroughly rebutted in the literature.
One of these papers is still cited regularly despite a more recent and more up-to-date similar analysis.
Some of them are in Big Name journals like Science, but many are in very technical and focused journals.
I’ve read nine of these papers, and I have cited six of them more than once. Eight are referenced in my book.
And making the list of the “most cited papers of all time” requires around 100,000 citations, no shark papers come close to that.
Papers that I did not count:
Edgar, G. J., Stuart-Smith, R. D., Willis, T. J., Kininmonth, S., Baker, S. C., Banks, S., … & Thomson, R. J. (2014). Global conservation outcomes depend on marine protected areas with five key features. Nature, 506(7487), 216-220. (1,365 citations) This paper is about MPAs in general, and while it mentions sharks they are not the foucs.
Hoffmann, M., et al.. (2010). The impact of conservation on the status of the world’s vertebrates. science, 330(6010), 1503-1509. (1,070 citations). This paper is about vertebrate conservation in general, and while it includes sharks it does not focus on them.
Block, B. A., et al. . (2011). Tracking apex marine predator movements in a dynamic ocean. Nature, 475(7354), 86-90. (1,003 citations). Six of the 23 species included in this study are sharks.
Maunder, M. N., & Punt, A. E. (2004). Standardizing catch and effort data: a review of recent approaches. Fisheries research, 70(2-3), 141-159. (1,003 citations). This paper focused on tunas but mentioned shark as bycatch in tuna fisheries.
Sims, D. W., Southall, E. J., Humphries, N. E., Hays, G. C., Bradshaw, C. J., Pitchford, J. W., … & Metcalfe, J. D. (2008). Scaling laws of marine predator search behaviour. Nature, 451(7182), 1098-1102. (770 citations). This paper is a review of animal telemetry work in general, which includes but does not focus on sharks.
Sandin, S. A., Smith, J. E., DeMartini, E. E., Dinsdale, E. A., Donner, S. D., Friedlander, A. M., … & Sala, E. (2008). Baselines and degradation of coral reefs in the Northern Line Islands. PloS one, 3(2), e1548. (713 citations). This was about overall reef ecosystems and not just sharks.
Humphries, N. E. et al.. (2010). Environmental context explains Lévy and Brownian movement patterns of marine predators. Nature, 465(7301), 1066-1069. (706 citations). This was about marine predators in general and not just sharks.
Taylor, G. K., Nudds, R. L., & Thomas, A. L. (2003). Flying and swimming animals cruise at a Strouhal number tuned for high power efficiency. Nature, 425(6959), 707-711. (699 citations). This was about a variety of marine animals not just sharks.