8. Jan, 2018

Voices of the sea

Luckily our world is still  full  of birds and insects that produce a variety of  sounds. Even the sounds of some insects are pleasant  to listen to. Like the songs of  crickets  and  the Cicadas or Cigales of the Provence in France. The male cicadas can produce exceptionally loud sounds by using two small membranes under each wing  that vibrate rapidly when pulled by tiny muscles. The male abdomen is largely hollow, and acts as a sound box, similar to a cello instrument.  On hot summer days whole groups of males congregate in the plane- or pine trees and synchronize their sound to establish chorusing centers that fill entire streets or market squares. The reason why is to attract the females. And perhaps also to entertain the summerguests having  lunch under the pine trees with a  glas of  cold vin rosee  within reach.

..Oops, almost forgot that this is about fishes not cicadas!  In contrast  with birds and  insects  the reputation of fishes is  not mainly based on the sounds that they make. Nevertheless, many fishes in the Atlantic or tropical oceans create different types of sounds using different mechanisms and for different reasons.  Research of sound production in fish is still in its infancy. But scientists using recorded fish vocalizations with underwater microphones have  identified many fish species that make amazing sounds, either as individuals or in groups.  Based on this evidence, it now seems that hundreds of species of marine (and probably also freshwater) fishes are capable of generating acoustic signals

Left: Upper figure: the sound producing mechanism of the catfish in the base of  its left pectoral fin (source **). Lower figure: swimbladder (SB), sonic muscle (SM) and  sonic nerve (SN) in the northern searobin (adapted from ***)

Active sound production in fish often depends on time and space. Many fishes become ‘talkative’ in the breeding season, following a seasonal and/or diurnal cycle.  In contrast with the sophisticated sonar sounds of  marine mammals like whales and dolphins, the vocabulary of fish species is limited, and meant to communicate gross information. It could signal danger, distress, competition or attracting a female. Fish vocalizations can take a wide variety of forms, including clicks, purrs, grunts, groans, growls or barks. They  may be intentionally produced as signals to predators or competitors, to attract mates or as territorial display. 

There are globally  two ways in which fishes make sounds. One is  stridulation:  striking or rubbing together skeletal components. Crickets use stridulation, as well as marine catfish and seahorses. For example seahorse species  make  clicking and/or snapping sounds by rubbing together  bony edges of the skull and  the coronet, a crown-shaped plate on the its head. These sounds are possibly amplified by the swim bladder. Some marine catfishes (Arius felis and Bagre marinus) have specialized pectoral fin spines that make a stridulatory squeaking sound. They do so by  rubbing the base of the pectoral fin spine against the pectoral girdle (see picture above). The sound can even be heard at the surface by anglers. Trigger fishes can produce drumroll sounds that result from alternate sweeping movements of the right and left pectoral fins, which push a system of three scutes (bony scales) that are forced against the swimbladder wall. Other fishes use their  swim bladder to produce sounds. A muscle attached to the swim bladder called the sonic muscle contracts and relaxes in a rapid sequence (see picture above). This action causes the swim bladder to vibrate and produce a low-pitched drumming sound. Examples are the goliath grouper, black drum, toad fish and silver peak. Not to forget the oyster toadfish, that is able to contract its muscle at a rate of 200 times a second. The  swim bladder can either function as the actual sound generator itself, or as an amplifier for sounds generated by other body parts including e.g. the pectoral girdle, fin rays, various other bones or tooth in front of the mouth.

Along coral reefs of the Red Sea clownfish, triggerfish, damselfish and angelfish often make loud clicks, drum rolls, or ‘pangs’ during agonistic interactions, in distress and or when divers get too close to their territory  (see audio gallery).  Other  male fishes, mostly found in the greater oceans or their coastlines  are known to create  very  strange and often very loud sounds. The sounds mostly serve to attract females in the mating or spawning seasons.  Here follow examples of some notorious sound producing species.

Catfish   Catfish can become very large and are found in  the sea, coastal water and rivers. The squeeker catfish  (Synodontis eupterus)  make a  croaking sound by rubbing the spines located in their pectoral fins into grooves on their shoulders as shown in the picture above. Talking catfish (Platydoras armatulus) can produce sound in two ways—by vibrating their swim bladder or by vibrating their pectoral fin spines in their sockets.

Oyster toadfish (Opsanus tau)   is a froglike fish from the  family  of Batrachoididae.  The fish has a distinctive "foghorn" sound used by males to attract females in the mating season (audio gallery and  toadfish song). Males make nests, and then attract females by "singing", that is, by releasing air by contracting muscles on their swim bladders.  Attracted by the foghorn sound, the female comes into the nest, lays eggs, and then leaves.The sound can be loud enough to be clearly audible from the surface. 

Plainfin midshipman (Porichthys notatus)  is bioluminescent. The plainfin midshipman is another type of toadfish, found off the west coast of North America from Alaska to Baja California. During the mating season the male midshipman hums—sometimes for long periods—by hitting his swim bladder with his sonic muscle. His humming serves to attract a female. Once she deposits her eggs, the midshipman resumes humming to attract another female to his nest. The male guards the eggs until they hatch. Typically these fishes are nocturnal and bury themselves in sand or mud in the intertidal zone during the day.

The black drum (Pogonias cromis) is a black or greyish fish that lives in the brackish water found in areas such as estuaries. The young fish have black stripes  that  fade as the fish matures. Black drums are mainly bottom feeders.  Adults can become very big and may weigh over a hundred pounds. Black drums become very noisy during the mating season  (audio gallery). The low pitched sounds that they produce travel long distances. Again,  males produce the sounds to attract females. The fish use their swim bladder and sonic muscle to create the vocalizations. Sometimes black drum  mating calls are conducted by the ground and the seawalls and then enter nearby houses on the shore.

Herring communicate with each other by expelling gas from the anal area, producing bubbles and a high-pitched sound. Inventive researchers have called this sound production a FRT (Fast Repetitive Tick). Both the Atlantic herring (Clupea harengus) and the Pacific herring (Clupea pallasii) produce FRTs. The fish swallow air from the water surface and then store it in the swim bladder, so the air is not the result of digesting food. During the night, in darkness and when surrounded by other herring, air is released through the anal duct. The purpose of the collective FRT sounds may be to ensure that the fish stay close together.

Corvina The physical act of reproduction can be a noisy affair for many fishes, but beats all records for the Gulf Corvina (Cynoscion othonopterus). Every spring, millions of these large gray fish migrate to the Colorado River delta and sync their spawning to the tides and the phases of the moon. The magnitude of their sounds (produced by rapidly beating their swim bladders with the sonic muscles) can become even deafening during simultaneous chorusing of males within the larger spawning aggregation.  These sounds  can even extend up to 27 km distance along the main channel of the Delta and include 1.5 million individuals during a single spawning period. At the loudest the sound level of the chorusing fishes was more than 150 decibels  (see  corvina). The corvina is endemic to the Northern Gulf of California and faces imminent risk of species extinction due to overfishing of its spawning aggregation,  and regulations that allow overfishing to persist*. In the spawning season local fisherman find it easy to locate the fishes by their sounds even from their small boats. With one net they often catch hundreds of corvina’s in a few minutes.

Sources and links

*Erisman BE, Rowell TJ. 2017 A sound worth saving: acoustic characteristics of a massive fish spawning aggregation. Biol. Lett. 13: 20170656

Popper AN, Fay RR, Platt C, Sand O. 2003 Sound detection mechanisms and capabilities of teleostfishes. In Sensory processing in aquatic environments(eds SP Collin, NJ Marshall), pp. 3–28. New York,NY: Berlin, Germany: Springer-Verlag.

Ben Wilson, Robert S. Batty and Lawrence M. Dill 2003. Pacific and Atlantic herring produce burst pulse sounds. Proc. R. Soc. Lond. B (Suppl.) 2003

**E. Parmentier et al. Functional study of the pectoral spine stridulation mechanism in different mochokid catfishes. Journal of Experimental Biology 2010 213: 1107-1114
Raick Xavier et al. Sound production mechanism in triggerfish (Balistidae): a synapomorphy
Journal of Experimental Biology 2017.  Published 23 November 2017
Tyack PL. 1998 Acoustic communication under the sea. In Animal acoustic communication (eds SL Hopp, MJ Owren, CS Evans), pp. 163–220. Berlin, Germany: Springer.
***Martin A. Connaughton  Sound generation in the searobin (Prionotus carolinus), a fish with alternate sonic muscle contraction. Journal of Experimental Biology 2004 207: 1643-1654

 Discovery of Sound in the Sea. University of Rhode Island and Inner Space Center. http://dosits.org/galleries/audio-gallery/fishes/ 

http://www.sfu.ca/biology/faculty/dill/publications/,FRTing_herring_Wilson_et_al.pdf (accessed August 26, 2017).