Otolith microchemical analysis

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Otolith microchemical analysis is a technique used in fisheries management and fisheries biology to delineate stocks and characterize movements, and natal origin of fish. The concentrations of elements and isotopes in otoliths are compared to those in the water in which the fish inhabits in order to identify where it has been. In non-ostariophysian fishes, the largest of the three otoliths, or ear bones, the sagitta is analyzed by one of several methods to determine the concentrations of various trace elements and stable isotopes. In ostariophysian fishes, the lapilli is the largest otolith and may be more commonly analysed.

Contents

Relevance

Fisheries management requires intimate knowledge of fish life history traits. Migration patterns and spawning areas are key life history traits in the management of many species. If a fish is migrating between two regions that are managed separately then it will be managed as two separate stocks unless this migration can be understood. If this migration is not discovered then overfishing of the stock may occur because managers assume there is double the amount of fish. In the past costly and inefficient tag and recapture studies were needed to discover such migration patterns. Today otolith microchemistry provides a simpler way to assess migration patterns of fish. Otolith microchemistry has been used to identify and delineate Atlantic cod stocks in Canadian waters. [1] It has also been used to determine the migratory patterns of anadromous whitefish. [2]

Natal origin is equally critical to understand because areas where fish spawn and inhabit during their critical larval period must be identified and protected. Natal origin is also important in determining whether regions are sources or sinks for stocks of fish. In the past natal origin had to be assumed based upon collection on spawning grounds. In recent years otolith microchemistry has shown that this is not always the case. It has provided an accurate way to assess the natal origin of fish without collecting them on the spawning grounds. Otolith microchemistry has been used to accurately identify estuarine nursery areas of fish. [3]

Chemical Composition

The otoliths begin to form shortly after the fish hatches. Otoliths are composed of a crystalline calcium carbonate structure, in the form of aragonite, on a protein matrix. Calcium carbonate is diffused through the endolymph cell membrane and the aragonite layers are permanently deposited in discrete increments. These increments are permanently stored in layers and their composition is not altered over time. Along with calcium carbonate, other chemicals are deposited in trace amounts. The most common trace elements found in otoliths are the alkaline earth metals Strontium (Sr), Barium (Ba), and Magnesium (Mg) because they are in the alkaline earth metal group like Calcium and therefore have the same bonding affinity. This allows these alkaline earth metals to substitute in for calcium in the aragonite without affecting the crystalline structure. Other elements and stable isotopes can be deposited in lower concentrations within the aragonite structure and in the protein matrix. The uptake of chemicals into the otolith is multi-stage and complex, but the chemical composition of the discrete layers are proportional to that of the ambient water in which the fish is inhabiting at the time of deposition. [4] These discrete layers create a temporal record of the water in which the fish has inhabited. There are 3 pairs of otoliths in bony fish, but only the largest, known as the saggita, is commonly used for microchemical analysis. The core of the otolith corresponds to the earliest larval period of the fish's life. Thus the microchemistry of the core of the otolith can be used as a means of inferring natal origin of fish. [1]

Analysis Methods

Water

A recent advance in approach to otolith microchemical analyses involves water chemistry analysis in conjunction with otolith microchemical analysis. [5] In order to standardize chemical concentrations, all elemental concentrations are recorded as proportion to Ca. The difference between fresh and salt (marine) water is the simplest to differentiate. Salt water has much higher concentrations of dissolved chemicals than freshwater. Despite numerous differences in chemical composition the two environments can be easily distinguished with just two elemental concentrations; Ba and Sr. Ba occurs in higher concentrations in freshwater and lower concentrations in marine waters. Inversely, Sr occurs in higher concentrations in marine waters and lower concentrations in freshwater. This relationship is clearly evident in otolith chemistry.

While delineating fresh waters from marine is relatively straightforward, finer-scale resolution is required to examine spatial and temporal variation within biomes. In freshwater environments, examining Sr87/Sr86 isotope ratios is often employed to provide greater spatial resolution. [5]

Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) are two common techniques that work by directing superheated plasma at the water sample and analyzing the gasses given off for trace amounts of different chemicals. Another Common technique is a beam based approach known as Proton-Induced X-ray Emission. In this technique a beam of protons is directed at the sample and the subsequent x-ray emissions are analyzed to determine chemical makeup of the sample.

Otolith

Once chemical signatures of regions of water are identified, the otoliths can be analyzed for comparison. Otoliths are examined and analyzed in one of two basic ways. The entire otolith can be sampled, or a portion of the otolith can be isolated through a targeted assay. [4] Both approaches begin with careful cleaning and preparation of the otoliths to be analyzed.

When data for fish movement over time or natal origin data is desired then a targeted portion approach is used. This approach is also known as a beam based approach because it uses a focused beam to analyze a small portion of the otolith at a time. All beam based techniques begin with cutting the otolith width wise through the core to reveal a cross section containing every layer from the origin outward. This section is placed in a polyester resin to hold it in position. A beam is then shot at the desired area and the chemical composition analyzed. For natal origin studies the core is analyzed. For temporal variation studies, a transect from the core through all the layers to the outer edge of the otolith is analyzed with the beam. Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICPMS) is the most accurate and versatile. LA-ICPMS has been used for numerous natal origin and temporal variation studies. [2] [6] The technique uses an extremely fine beam laser to ablate, or burn away, a very shallow layer of the otolith. The emissions from this are then analyzed for chemical composition.

Stable isotope values of otoliths have also been used to determine climate in the past [7] Fish otoliths as old as 172 million years have been used to study the environment in which the fish lived. [8] Robotic micromilling devices have been used to recover very high resolution records of diet, life history and temperatures throughout the life of the fish, including their natal origin [9]

Related Research Articles

Calcium Chemical element, symbol Ca and atomic number 20

Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The name derives from Latin calx "lime", which was obtained from heating limestone.

Limestone Sedimentary rocks made of calcium carbonate

Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes have likely been more important for the last 540 million years. Limestone often contains fossils, and these provide scientists with information on ancient environments and on the evolution of life.

Strontium Chemical element, symbol Sr and atomic number 38

Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to air. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these.

Calcite Carbonate mineral and polymorph of calcium carbonate

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 3 as "calcite".

Calcium carbonate Chemical compound

Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone, which is a type of sedimentary rock consisting mainly of calcite) and is the main component of eggshells, snail shells, seashells and pearls. Calcium carbonate is the active ingredient in agricultural lime and is created when calcium ions in hard water react with carbonate ions to create limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.

Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated by catabolism and excretion. Thus, the longer the biological half-life of a toxic substance, the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. Bioaccumulation, for example in fish, can be predicted by models. Hypotheses for molecular size cutoff criteria for use as bioaccumulation potential indicators are not supported by data. Biotransformation can strongly modify bioaccumulation of chemicals in an organism.

Isotope analysis

Isotope analysis is the identification of isotopic signature, the abundance of certain stable isotopes and chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web, to reconstruct past environmental and climatic conditions, to investigate human and animal diets in the past, for food authentification, and a variety of other physical, geological, palaeontological and chemical processes. Stable isotope ratios are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio.

Aragonite Calcium carbonate polymorph

Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, CaCO3 (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including precipitation from marine and freshwater environments.

Fish migration Movement of fishes from one part of a water body to another on a regular basis

Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Fish usually migrate to feed or to reproduce, but in other cases the reasons are unclear.

Short-finned eel Species of fish

The short-finned eel, also known as the shortfin eel, is one of the 15 species of eel in the family Anguillidae. It is native to the lakes, dams and coastal rivers of south-eastern Australia, New Zealand, and much of the South Pacific, including New Caledonia, Norfolk Island, Lord Howe Island, Tahiti, and Fiji.

Otolith

An otolith, also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The saccule and utricle, in turn, together make the otolith organs. These organs are what allows an organism, including humans, to perceive linear acceleration, both horizontally and vertically (gravity). They have been identified in both extinct and extant vertebrates.

Carbonate compensation depth (CCD) is the depth in the oceans below which the rate of supply of calcite lags behind the rate of solvation, such that no calcite is preserved. Shells of animals therefore dissolve and carbonate particles may not accumulate in the sediments on the sea floor below this depth. Aragonite compensation depth describes the same behaviour in reference to aragonitic carbonates. Aragonite is more soluble than calcite, so the aragonite compensation depth is generally shallower than the calcite compensation depth.

Hydroacoustics The study and technological application of sound in water

Hydroacoustics is the study and application of sound in water. Hydroacoustics, using sonar technology, is most commonly used for monitoring of underwater physical and biological characteristics.

Natal homing, or natal philopatry, is the homing process by which some adult animals return to their birthplace to reproduce. This process is primarily used by aquatic animals, such as sea turtles and Pacific salmon. Scientists believe that the main cues used by the animals are geomagnetic imprinting and olfactory cues. The benefits of returning to the precise location of an animal's birth may be largely associated with its safety and suitability as a breeding ground. When seabirds, like the Atlantic puffin, return to their natal breeding colony, which are mostly on islands, they are assured of a suitable climate and a sufficient lack of land-based predators.

This is a glossary of terms used in fisheries, fisheries management and fisheries science.

Freshwater environmental quality parameters

Freshwater environmental quality parameters are those chemical, physical or biological parameters that can be used to characterise a freshwater body. Because almost all water bodies are dynamic in their composition, the relevant quality parameters are typically expressed as a range of expected concentrations.

Oolitic aragonite sand

Oolitic aragonite sand is composed of the calcium carbonate mineral, aragonite, with an egg-like shape and sand grain size. This sand type forms in tropical waters through precipitation, sedimentation, and microbial activity, and is indicative of high energy environments. The production of oolitic aragonite sand in the Bahamas surpasses anyplace else in the world. Changes in seawater chemistry and paleoenvironments can be interpreted by the sand's chemical composition and structure.

The following outline is provided as an overview of and topical guide to fisheries:

Shell growth in estuaries

Shell growth in estuaries is an aspect of marine biology that has attracted a number of scientific research studies. Many groups of marine organisms produce calcified exoskeletons, commonly known as shells, hard calcium carbonate structures which the organisms rely on for various specialized structural and defensive purposes. The rate at which these shells form is greatly influenced by physical and chemical characteristics of the water in which these organisms live. Estuaries are dynamic habitats which expose their inhabitants to a wide array of rapidly changing physical conditions, exaggerating the differences in physical and chemical properties of the water.

Stable isotope ratio

The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally, yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry.

References

  1. 1 2 Campana, S. E., Fowler, A. J. and C. M. Jones. 1994. Otolith elemental fingerprinting for stock identification of Atlantic cod (Gadus morhua). Canadian journal of fisheries and aquatic science 51: 1942–1950
  2. 1 2 Halden, N.M. and L.A. Friedrich. 2008. Trace-element distribution in fish otoliths: natural markers of life histories, environmental conditions and exposure to tailings effluence. Mineralogical Magazine 73:593-605.
  3. ↑ Thorrold, S. R., Jones, C. M., Swart, P. K. and T. E. Targett. 1998. Accurate classification of juvenile weakfish Cyniscion regalis to estuarine nursery areas based on chemical signatures in otoliths. Marine ecology progress series 173: 253-265
  4. 1 2 Campana, S. E. 1999. Chemistry and composition of fish otoliths: pathways, mechanisms and applications. Marine Ecology Progress Series 188: 263-297.
  5. 1 2 Starrs, D; Ebner, B; Fulton, C (November 25, 2014). "All in the ears: unlocking the early life history biology and spatial ecology of fishes". Biological Reviews. 91 (1): 86–105. doi:10.1111/brv.12162. PMID   25424431. S2CID   19533349.
  6. ↑ Mohan, J.A. 2009. Habitat utilization of juvenile striped bass (Morone saxatili)s in Albemarle Sound inferred from otolith and water chemistries. MS Thesis. East Carolina University, Greenville, NC
  7. ↑ Patterson, William P.; Smith, Gerald R.; Lohmann, Kyger C. (2013). "Continental Paleothermometry and Seasonality Using the Isotopic Composition of Aragonitic Otoliths of Freshwater Fishes". Climate Change in Continental Isotopic Records. Geophysical Monograph Series. pp. 191–202. doi:10.1029/GM078p0191. ISBN   9781118664025.
  8. ↑ Patterson, William P. (1999). "Oldest isotopically characterized fish otoliths provide insight to Jurassic continental climate of Europe". Geology. 27 (3): 199. doi:10.1130/0091-7613(1999)027<0199:OICFOP>2.3.CO;2.
  9. ↑ Zazzo, A.; Smith, G.R.; Patterson, W.P.; Dufour, E. (2006). "Life history reconstruction of modern and fossil sockeye salmon (Oncorhynchus nerka) by oxygen isotopic analysis of otoliths, vertebrae, and teeth: Implication for paleoenvironmental reconstructions" (PDF). Earth and Planetary Science Letters. 249 (3–4): 200–215. doi:10.1016/j.epsl.2006.07.003.
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