BASTERIA, 66:113-120, 2002 Mass stranding of cuttlebones ofSepia orbignyana Férussac, 1826, on Texel, the Netherlands, in July 2002 (Cephalopoda, Decapoda, Sepiidae) Gerhard+C. Cadée Netherlands Institute for Sea Research (NIOZ), EO. Box 59, NL 1790 AB Den Burg, The Netherlands; [email protected] A occurred the coast of mass stranding of hundreds of cuttlebones of Sepia orbignyana on in Texel, the Netherlands, July 2002. Up to now usually only low numbers were found on the Dutch coast. S. orbignyana does not live in the North Sea. Accompanying drift material such as thongweed Himanthaliaelongata indicates a SW origin from the Channel and skeletons of the Velella velella indicate By-the-wind-sailor (Cnidaria, Hydrozoa, Chondrophora)may even anorigin from as far as the Bay ofBiscay. Drift-bottle experiments in the past have indicated that it takes at least one to two months to drift from the entrance of the Channel near Plymouth to the Dutch coast. A large proportion of the cuttlebones (65%) showed peck 55% drif- marks by fulmars and had scratch marks probably also made by birds supportinga ting time ofthis length. Key words: Cephalopoda,Sepia orbignyana, mass stranding, North Sea, The Netherlands. INTRODUCTION Shells of the most common North Sea cuttlefish, Sepia officinalis L., 1758, often wash in ashore in large numbers together; thousands may be found on the beach the summer of Lacourt, 1957b; Lacourt Huwae, Cadee, some years (Altena, 1937; & 1981; 1997a,b). The same occurs along the German North Sea coast (Grimpe, 1925; Schafer, 1964). Such related the fact that after the of their mass strandings are partly to spawning, in summer second most female S. die. Lower numbers of two less year, officinalis common species, S. and S. from the viz. elegans Orbigny, 1839, orbignyana Ferussac, 1826, are reported Dutch coast and S. orbignyana is the least frequent according to Altena (1937) and the therefore Lacourt (1957a), who summarised older data for these species. It was a great surprise to find hundreds of S. orbignyana cuttlebones washed ashore on Texel be- and This this tween 8 12 July 2002. note reports on mass stranding. OBSERVATIONS A three km length ofbeach in the southern part ofTexel between Hoornderslag and de Hors - an area less frequented by tourists - was selected to collect and count all S. orbignyana cuttlebones stranded on four different days between 8 and 12 July. In total I cuttlebones. The picked up c. 600 specimens selecting only intact or almost intact intact specimens (240) enabled measurements to be taken to the nearest 0.1 mm of length (including the spine) and width (ofthe calcareous body of the cuttlebone, discarding the horny margins) using a vernier caliper. The length ranged from 24.0 to 117.5 mm. 114 BASTERIA, Vol. 66, No. 4-6, 2002 and width correlated =0.974, <0.0001, I measured the width Length were (r p fig. 1). only of 265 ofthe incomplete specimens in which length could not be measured. Histograms of length and width distribution could be constructed (figs. 2 and 3). Both histograms show distributionwith 'adult' between and clearly a bimodal an peak 100 110 mm length and 29 to 32 mm width and a 'juvenile' peak at 50 to 60 mm length and 14 to 17 mm width. No S. shells washed ashore after the 12th of because the wind new orbignyana July of winds direction changed for some time to the east. During a new period westerly at the end of July, however, S. orbignyana shells again washed ashore: 78 fresh shells were collected on the 26th ofJuly (intact and broken but larger than half cuttlebones; smaller the of the beach visited between 8 and 12 fragments were discarded), on same part July. The mass stranding was preceded and accompanied by numerous shells of S. officina- lis of which I collected the first washed ashore the southern of Texel the 4th on part on of July. Altena (1937) observed a similar sequence in 1924. During the mass stranding of S. shells those of S. remained the 9th of I orbignyana officinalis more numerous: on July counted 127 shells of S. officinalis against 43 of S. orbignyana in fresh drift along part of the beach. The large sample madeit possible to quantify the occurrenceof epiphytes and epizoa, as well as the damage by birds exemplified by peck marks, as has been reported earlier for cuttlebones ofSepia officinalis washed ashore on Texel (Cadee, 1997a,b). Remarkable the almost absence of S. shells: small barnacles was epizoa on orbignyana two (1 mm length, Elminius modestus Darwin, 1851) were found only on one specimen out of the 310 studied for this the and selected incom- purpose (all 240 intact specimens 70 randomly Green plete specimens). algae (Enteromorpha sp.) occurred on 70% of the cuttlebones, marks birds and rectilinear scratches of unknown peck by (fig. 4) on 65% (fig. 5) origin but probably also by birds on 55%. Fig. 1. Length/width ratio of 240 Sepia orbignyana shells from Texel, collected 8-12 July 2002. Cade'e: Sepia orbignyana on Texel 115 DISCUSSION EarlierDutch reports Unfortunately, the olderrecords ofS. orbignyana not always give exact numbers ofcutt- lebones found the on beach, particularly when the numbers are somewhat higher, they often state whereas to count numbers simply 'many', we now usually try per length unit of beach. Nevertheless, from the records that S. cutt- it appears orbignyana and S. elegans lebones often wash ashore and in S. is the least of together general orbignyana common the two (Altena, 1937; Lacourt, 1957a). The largest numbers of S. orbignyana given by Altena 30 for aan Zee and 4 and also (1937) are Egmond (3 August 1924) once 'many' in the 26th of 1924 on July at Scheveningen. Since 1936many records are assembled in the "CentraalSysteem" (CS) of the "Strandwerkgroep" (SWG) of which the most important records are published regularly in Het Zeepaard. Lacourt (1957a, 1963) has published on these data and Dr. R de Wolf(NIOZ) has assembled all available data from the second half ofthe 19th century (published in Altena, 1937) to 2001 (CS-SWG). Tom Meijer col- lected now the number of S. the Dutch up to highest orbignyana on coast on one day (84 CS-SWG, comm. specimens in 1964, pers. P. de Wolf, 2002). This makes our observation of 600 3 km beach indeed also observed S. specimens per exceptional. Moreover, we cuttlebones orbignyana on the beach near the northern part ofTexel in the same period. This indicates that washed ashore the whole ofthe Sea they along length ca 30 km North coast ofTexel, and the total amount stranded injuly 2002 onTexel alonemust have been thousands. We did find shell of S. not one elegans in our rich material, although both Altena (1937) and Lacourt (1957) conclude that shells of S. orbignyana and S. elegans wash ashore in low numbers but often together, with S. elegans being the most abundant. According to al. S. SW Hayward et (1996) orbignyana is rare off Britain, S. elegans is uncommon in coastal waters of W Britain. So S. orbignyana lives farther to the SW than S. elegans. Hayward & Ryland (1995) do not even mentionS. orbignyana. As the cuttleboneswashed ashore in 2002 together with skeletons of Velella velella (L., 1758) (Cnidaria, Hydrozoa, & Cadee - Coenen, which Chondrophora) (Cadee 2002), is an open-ocean warm-water surface drifter, this indicates that the material washed ashore Texel had least on at part- ly an open oceanorigin. The shells of S. orbignyana must have drifted for weeks. Peck marks The triangular peck marks were similar to those observed earlier on cuttlebones of S. made Fulmarus officinalis; they are at sea by northernfulmars, glacialis glacialis (L., 1758), indicated the ofthe marks I do as by peculiar triangular shape (Cadee, 1997a). not agree with Brown et al. who describe (1987: p. 77) comparable triangular peck marks in cutt- lebones as due to common gulls. Lulmars might use the calcareous matter of the cuttle- but all bones, more probable they simply peck at floating objects, ingesting the smaller floating particles, including indigestable plastics (Van Lraneker & Meijboom, 2002) and at the pecking larger particles such as cuttlebones and styrofoam and other spongy plastics (Cadee, 2002). The rectilinear scratches are probably also madeby birds. My hypothesis is that some birds take the cuttlebones transverse in their bill, the scratches being due to the beak 116 BASTERIA, Vol. 66, No. 4-6, 2002 Figs 2-3. Size-frequency distributions of Sepia orbignyana shellsfrom Texel collected 8-12 July 2002. 2, length (in 10-mm classes) of 240 shells; 3, width of 505 shells (in 3-mm classes). in the of the which margins. They occur particular on convex centre part shells, supports this hypothesis. I have no direct observations, however, Herring gulls do transport Ensis directus (Conrad, 1845) also transverse in their bill (Cadee, 2000), which suggests gulls cuttlebones in might pick up of comparable shape and size a similar way. Cade'e: Sepia orbignyana on Texel 117 Origin ofthe cuttlebones Together with the shells of this warm and relatively deep water S. orbignyana (down to 450 m and avoiding shallow coastal waters according to Mangold-Wirz, 1963) thong weed Himanthalia elongata (L.) S.F. Gray washed ashore, which indicates a southern ori- of the drift, as the where this is the Channel west of gin nearest place alga grows English - Cotentin the line Wight (Den Hartog, 1959). Also hundreds of skeletons of the warm- Velella velella, which elsewhere water open-ocean By-the-wind-sailor on we reported (Cadee & Cadee - Coenen, 2002), were washed ashore. These species together are a cer- indication of south-western is tain a provenance of the drift.