What’s in your Tacos?

“I can see that it’s meat, but what species?” is a question that travelers may find themselves asking until they learn that it’s better not to. Oddly, few ever ask a similar question about fish. Restaurants commonly advertise fish tacos, fish chowder, or pasta with fish sauce without feeling any need to state the species. This is especially surprising given that fish represent roughly half of all living vertebrates meaning that, at least in terms of species precision, it would be less problematic to sell food labeled only as ‘mammal’ or ‘bird’.

This may soon change in California. State senator Alex Padilla has recently introduced SB1138, a bill that would require all seafood sold in California to be labeled with the fish’s common name and would make selling mislabeled seafood a crime. While I support this bill and think it’s a good first step, I personally think that fish should be labeled with its scientific name as well.

Organisms are usually referred to by their genus and species in the scientific literature. Genus is listed before species and capitalized, while species is written in all lowercase. While there can be multiple species with a genus such as lions, leopards, tigers, and jaguars all being members of the genus Panthera (P. leo, P. pardus, P. tigris, and P. onca respectively), every described species should have exactly one unique genus species combination.

Common names cannot achieve this level of precision. Many fish species are marketed under more than one common name, often because their original names were deemed unappealing to consumers. Classic examples of this include labeling Dissostichus eleginoides as Chilean seabass rather than Patagonian toothfish, Squatinia squatina as monkfish rather than angelshark, and Coryphaena hippurus as mahi-mahi or dorado rather than dolphinfish.

Furthermore, it is not unusual for very different fish species to share common names. Squatina squatina (angelshark) and anglerfish in the genus Lophius are all marketed as monkfish, four species of fish have the common name of black cod (http://en.wikipedia.org/wiki/Black_cod), and any species of fish in the family Lutjanidae (110 species total http://www.fishbase.org/summary/FamilySummary.php?ID=323) can be sold as snapper. As you can imagine this leaves room for a lot of variability in terms of well or poorly managed fisheries as well as levels of mercury contamination. This makes it hard for consumers to make good decisions regarding sustainability or their health. Labeling fish with its scientific as well as common name will help clarify this issue.

Lophius spp. I can see why they're usually sold as fillets.
Lophius spp. I can see why they’re usually sold as fillets.
Angelshark. And they say I have a big mouth. (Image from wikipedia.)
Angelshark. And they say I have a big mouth. (Image from wikipedia.)










It is true that few non-scientists are familiar with the scientific names of commonly consumed fishes, but non-scientists could still use this information. Smartphones have become ubiquitous in California and now most of us are never more than a few seconds away from finding out whether we are better off purchasing Pagrus auratus (New Zealand tai) or Aphareus rutilans (rusty jobfish). According to Seafood Watch the latter is much more sustainable.






The Ultimate Mesopredator

The idea of the apex predator has banged around popular culture long enough that almost everybody knows what it means. It refers to animals at the top of the food chain like killer whales, great white sharks, lions, tigers, and bears (oh my!). The term mesopredator, however, is rarely seen outside of scientific literature. Nonetheless, this label refers to animals such as raccoons, baboons, and stingrays. These carnivorous or omnivorous animals occupy the middle of the food chain hunting those at the bottom and being hunted by those at the top.

Sector Murcielago, Guanacaste, Costa Rica 2008. Don't worry, the grill was not on.
Sector Murcielago, Guanacaste, Costa Rica 2008. Don’t worry, the grill was not on.


As anyone on the mailing list for any environmental charity knows, apex predators are declining around the world. (The findings of Burgess et al. 2014 suggest that great white sharks in California may be an exception to this trend). While the decline of apex predators certainly results in a loss for biodiversity, it has led to extreme gains by mesopredators.


In their dramatically titled review “The Rise of the Mesopredator”, Prugh et al. (2009) introduce the concept of mesopredator release. This refers to the explosion of mesopredator populations that occurs once apex predators have been removed from an ecosystem. This can, in turn, lead to population collapses of the mesopredators’ prey. Humans may attempt to address this problem by culling mesopredators, but the high fertility rates of these species (Palomares et al. 1995) may reduce culling programs to ecological whack-a-mole.


Truthfully, controlling mesopredators may be difficult because of their ecological similarity to our own species. While humans currently occupy the top of the food chain, we had to fight our way to it. Once our ancestors learned to cooperate, use fire, throw rocks, and set traps they were able to drive their predators as well as much of their prey to extinction or increasingly small refuge habitat.


In spite of our newfound ecological dominance we still behave like mesopredators. We remain omnivorous and abundant (7 billion strong) and our numbers are increasing at a rate of roughly 80 million per year (http://www.worldometers.info/world-population/#growthrate). We may even be the most abundant mammalian mesopredator on the planet, although we will probably never know for sure because rats are difficult to census. Furthermore, I think we can claim the title of ‘Ultimate Mesopredator’ because the rise of our species paved the way for all the rest.


While humans celebrate the ascension of our own species, many of us are less than thrilled that other mesopredators came along for the ride. Rats are notorious plague vectors, baboons raid crops, and misunderstandings between humans and stingrays became infamous with the death of Steve Irwin. It is difficult for humans to control populations of these species, but apex predators seem to be quite good at it (Prugh et al. 2009). This means that any effort to reduce the negative impacts of mesopredator release will require allowing surviving apex predator species to go the way of the great white shark rather than the saber-toothed tiger. Obviously, this strategy will be somewhat scary to the Ultimate Mesopredator, but Steve Irwin would approve.



Burgess GH, Bruce BD, Caillet GM, Goldman KJ, Grubbs RD, Lowe CG, MacNeill MA, Mollet HF, Weng KC, O’Sullivan JB. 2014. A Re-Evaluation of the Size of the White Shark (Charcharodon carcharias) Population off California, USA. PLoS One 9(6). Burgess at al. 2014

Palomares F, Gaona P, Ferreras P, Delibes M. 1995. Positive Effects on Game Species of Top Predators by Controlling Smaller Predator Populations: An Example with Lynx, Mongooses, and Rabbits. Conservation Biology 9, 295-305 Palomares et al. 1995

Prugh LR, Stoner CJ, Epps CW, Bean WT, Ripple WJ, Laliberte AS, Brashares JS. 2009. The Rise of the Mesopredator. Bioscience 59(9), 779-791. the rise of the mesopredator